研究者データベース

武次 徹也(タケツグ テツヤ)
理学研究院 化学部門 物理化学分野
教授

基本情報

所属

  • 理学研究院 化学部門 物理化学分野

職名

  • 教授

ホームページURL

J-Global ID

研究キーワード

  • 量子化学   反応動力学   理論化学   計算化学   

研究分野

  • ナノテク・材料 / 基礎物理化学 / 理論化学

職歴

  • 2005年04月 - 現在 北海道大学 大学院理学研究院化学部門 教授
  • 1999年04月 - 2005年03月 お茶の水女子大学 理学部化学科 助教授
  • 1995年11月 - 1999年03月 東京大学 大学院工学系研究科応用化学専攻 助手
  • 1994年 - 1995年 アイオワ州立大学 博士研究員
  • 1994年 - 1995年 Researcher,Iowa State University

学歴

  •         - 1994年   東京大学   大学院工学系研究科   工業化学専攻 博士後期課程
  •         - 1994年   東京大学
  •         - 1991年   東京大学   大学院工学系研究科   合成化学専攻 修士課程
  •         - 1991年   東京大学
  •         - 1989年   東京大学   工学部   合成化学科

所属学協会

  • 理論化学会   American Chemical Society   分子科学会   日本化学会   

研究活動情報

論文

  • Geometric Analysis of Anharmonic Downward Distortion Following Paths
    Shuichi Ebisawa, Takuro Tsutsumi, Tetsuya Taketsugu
    Journal of Computational Chemistry 2020年10月 [査読有り][通常論文]
  • Satoshi HINOKUMA, Takeshi IWASA, Kento ARAKI, Yusuke KAWABATA, Shun MATSUKI, Tetsuya SATO, Yoshihiro KON, Tetsuya TAKETSUGU, Kazuhiko SATO, Masato MACHIDA
    Journal of the Japan Petroleum Institute 63 5 274 - 281 2020年09月01日 [査読有り][通常論文]
  • Masato Kobayashi, Mei Harada, Hideo Takakura, Kanta Ando, Yuto Goto, Takao Tsuneda, Mikako Ogawa, Tetsuya Taketsugu
    ChemPlusChem 85 9 1959 - 1963 2020年09月 [査読有り][通常論文]
  • Takuro Tsutsumi, Yuriko Ono, Zin Arai, Tetsuya Taketsugu
    Journal of Chemical Theory and Computation 16 7 4029 - 4037 2020年07月14日 [査読有り][通常論文]
  • Ahmed S. Abdel-Bary, Dina A. Tolan, Mostafa Y. Nassar, Tetsuya Taketsugu, Ahmed M. El-Nahas
    International Journal of Biological Macromolecules 154 621 - 633 2020年07月 [査読有り][通常論文]
  • Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada, Kenta Kokado
    Chemistry – A European Journal 26 36 8028 - 8034 2020年06月26日 [査読有り][通常論文]
  • Yusuke Ootani, Aya Satoh, Yu Harabuchi, Tetsuya Taketsugu
    Journal of Computational Chemistry 41 16 1549 - 1556 2020年06月15日 [査読有り][通常論文]
  • Masato Takenaka, Tetsuya Taketsugu, Takeshi Iwasa
    The Journal of Chemical Physics 152 16 164103 - 164103 2020年04月30日 [査読有り][通常論文]
  • Jiade Li, Min Gao, Shengfu Tong, Cuiping Luo, Huaiyong Zhu, Tetsuya Taketsugu, Kohei Uosaki, Mingmei Wu
    Electrochimica Acta 340 135977 - 135977 2020年04月 [査読有り][通常論文]
  • Rui Han, Jiangyong Diao, Sonu Kumar, Andrey Lyalin, Tetsuya Taketsugu, Gilberto Casillas, Christopher Richardson, Feng Liu, Chang Won Yoon, Hongyang Liu, Xudong Sun, Zhenguo Huang
    Journal of Energy Chemistry 2020年04月 [査読有り][通常論文]
  • Ken Sakaushi, Andrey Lyalin, Tetsuya Taketsugu
    Current Opinion in Electrochemistry 19 96 - 105 2020年02月 [査読有り][招待有り]
  • Jaculbia, R.B, Imada, H, Miwa, K, Iwasa, T, Takenaka, M, Yang, B, Kazuma, E, Hayazawa, N, Taketsugu, T, Kim, Y
    Nature Nanotechnology 15 105 - 110 2020年01月20日 [査読有り][通常論文]
  • Ben Wang, Min Gao, Kohei Uosaki, Tetsuya Taketsugu
    Physical Chemistry Chemical Physics 22 21 12200 - 12208 2020年 [査読有り][通常論文]
     

    A periodicity implemented scheme of NBO theory and normal mode analysis has been employed to investigate the chemical bond strength tendency for aryl isocyanide molecules with different para-substituted groups adsorbed on the Pt(111) surface.

  • Nikolay A. Vinogradov, Andrey Lyalin, Tetsuya Taketsugu, Alexander S. Vinogradov, Alexei Preobrajenski
    ACS Nano 13 12 14511 - 14518 2019年12月24日 [査読有り][通常論文]
  • Masato KOBAYASHI, Haruka ONODA, Yusuke KURODA, Tetsuya TAKETSUGU
    Journal of Computer Chemistry, Japan 18 5 251 - 253 2019年12月 [査読有り][通常論文]
  • Takao Tsuneda, Takeshi Iwasa, Tetsuya Taketsugu
    The Journal of Chemical Physics 151 9 094102 - 094102 2019年09月07日 [査読有り][通常論文]
  • Wei Shyang Tan, Ting‐Yin Lee, Sheng‐Fang Tseng, Ying‐Feng Hsu, Masanori Ebina, Tetsuya Taketsugu, Shing‐Jong Huang, Jye‐Shane Yang
    Journal of the Chinese Chemical Society 66 9 1141 - 1156 2019年09月 [査読有り][通常論文]
  • Yu Harabuchi, Ryosuke Tani, Nuwan De Silva, Bosiljka Njegic, Mark S. Gordon, Tetsuya Taketsugu
    The Journal of Chemical Physics 151 6 064104 - 064104 2019年08月14日 [査読有り][通常論文]
  • Ahmed A. Galhoum, Emad A. Elshehy, Dina A. Tolan, Ahmed M. El-Nahas, Tetsuya Taketsugu, Kaoru Nishikiori, Takaya Akashi, Asmaa S. Morshedy, Eric Guibal
    Chemical Engineering Journal 375 121932-1 - 121932-16 2019年06月 [査読有り][通常論文]
  • Xinlong Li, Min Gao, Naoki Hiroyoshi, Carlito Baltazar Tabelin, Tetsuya Taketsugu, Mayumi Ito
    Minerals Engineering 138 226 - 237 2019年05月 [査読有り][通常論文]
  • Yukatsu Shichibu, Mingzhe Zhang, Takeshi Iwasa, Yuriko Ono, Tetsuya Taketsugu, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, Katsuaki Konishi
    Journal of Physical Chemistry C 123 11 6934 - 6939 2019年03月21日 [査読有り][通常論文]
     
    © Copyright 2019 American Chemical Society. The use of multidentate chelating ligands enriches the geometric diversity of coordinated gold clusters, offering much knowledge to benefit the understanding of their unique electronic structures and optical properties. Herein we report different behaviors of [core+exo]-type Au6 clusters bearing C3- and C4-bridged diphosphines (1 and 2), highlighting profound effects of the steric constraints of the ligand environments on the excited-state structural dynamics. Although the Au6 geometries of 1 and 2 in the crystalline states were somewhat different, their absorption spectra in solution were almost similar. However, marked differences were found in the photoluminescence properties; phosphorescent-type emission was dominantly observed for 1, whereas 2 gave both fluorescence- and phosphorescence-type emissions. Theoretical calculations showed that the bridging chains influence the geometries of the Au6 unit in the excited states, leading to the observed differences in emission behaviors.
  • Ebina Masanori, Kondo Yusuke, Iwasa Takeshi, Taketsugu Tetsuya
    INORGANIC CHEMISTRY 58 7 4686 - 4698 2019年03月 [査読有り][通常論文]
  • Hinokuma Satoshi, Araki Kento, Iwasa Takeshi, Kiritoshi Saaya, Kawabata Yusuke, Taketsugu Tetsuya, Machida Masato
    CATALYSIS COMMUNICATIONS 123 64 - 68 2019年02月 [査読有り][通常論文]
  • Tetsuya Taketsugu, Yuta Kobayashi
    Computational and Theoretical Chemistry 1150 1 - 9 2019年02月 [査読有り][招待有り]
  • Lyalin Andrey, Kuznetsov Vladimir G, Nakayama Akira, Abarenkov Igor V, Tupitsyn Ilya I, Gabis Igor E, Uosaki Kohei, Taketsugu Tetsuya
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 166 3 A5362 - A5368 2019年01月19日 [査読有り][通常論文]
  • Muneaki Kamiya, Tetsuya Taketsugu
    Journal of Computational Chemistry 40 2 456 - 463 2019年01月15日 [査読有り][招待有り]
  • Kondo Yusuke, Takahara Rina, Mohri Hirono, Takagi Makito, Maeda Satoshi, Iwasa Takeshi, Taketsugu Tetsuya
    JOURNAL OF COMPUTER CHEMISTRY-JAPAN 18 1 64 - 69 2019年01月 [査読有り][通常論文]
  • Markus Eckardt, Ken Sakaushi, Andrey Lyalin, Maximilian Wassner, Nicola Hüsing, Tetsuya Taketsugu, Rolf Jürgen Behm
    Electrochimica Acta 299 736 - 748 2019年01月 [査読有り][通常論文]
  • Konstantin A. Simonov, Alexander V. Generalov, Alexander S. Vinogradov, Gleb I. Svirskiy, Attilio A. Cafolla, Cormac McGuinness, Tetsuya Taketsugu, Andrey Lyalin, Nils Mårtensson, Alexei B. Preobrajenski
    Scientific Reports 8 1 3506  2018年12月01日 [査読有り][通常論文]
     
    We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules on Ag(111) with the focus on the role of the organometallic (OM) intermediates. It is demonstrated that DBBA molecules on Ag(111) are partially debrominated at room temperature and lose all bromine atoms at elevated temperatures. Similar to DBBA on Cu(111), debrominated molecules form OM chains on Ag(111). Nevertheless, in contrast with the Cu(111) substrate, formation of polyanthracene chains from OM intermediates via an Ullmann-type reaction is feasible on Ag(111). Cleavage of C-Ag bonds occurs before the thermal threshold for the surface-catalyzed activation of C-H bonds on Ag(111) is reached, while on Cu(111) activation of C-H bonds occurs in parallel with the cleavage of the stronger C-Cu bonds. Consequently, while OM intermediates obstruct the Ullmann reaction between DBBA molecules on the Cu(111) substrate, they are required for the formation of polyanthracene chains on Ag(111). If the Ullmann-type reaction on Ag(111) is inhibited, heating of the OM chains produces nanographenes instead. Heating of the polyanthracene chains produces 7-AGNRs, while heating of nanographenes causes the formation of the disordered structures with the possible admixture of short GNRs.
  • Takeshi Iwasa, Takaaki Sato, Makito Takagi, Min Gao, Andrey Lyalin, Masato Kobayashi, Ken-ichi Shimizu, Satoshi Maeda, Tetsuya Taketsugu
    The Journal of Physical Chemistry A 123 210 - 217 2018年12月 [査読有り][通常論文]
  • Sreekanta Debnath, Xiaowei Song, Matias Fagiani, Marissa Weichman, Min Gao, Satoshi Maeda, Tetsuya Taketsugu, Wieland Schöllkopf, Andrey Lyalin, Daniel Neumark, Knut Asmis
    The Journal of Physical Chemistry C 123 8439 - 8446 2018年12月 [査読有り][招待有り]
  • Saaya Kiritoshi, Takeshi Iwasa, Kento Araki, Yusuke Kawabata, Tetsuya Taketsugu, Satoshi Hinokuma, Masato Machida
    RSC Advances 8 41491 - 41498 2018年12月 [査読有り][通常論文]
  • Yusuke Kuroda, Masato Kobayashi, Tetsuya Taketsugu
    Chemistry Letters 48 137 - 139 2018年12月 [査読有り][通常論文]
  • Ken Sakaushi, Andrey Lyalin, Tetsuya Taketsugu, Kohei Uosaki
    Physical Review Letters 121 236001  2018年12月 [査読有り][通常論文]
  • Masato Takenaka, Yoshikazu Hashimoto, Takeshi Iwasa, Tetsuya Taketsugu, Gediminas Seniutinas, Armandas Balčytis, Saulius Juodkazise, Yoshiaki Nishijima
    Journal of Computational Chemistry 40 925 - 932 2018年10月 [査読有り][通常論文]
  • Takao Tsuneda, Tetsuya Taketsugu
    Physical Chemistry Chemical Physics 20 24992 - 24999 2018年09月 [査読有り][通常論文]
  • Yasuchika Hasegawa, Yui Miura, Yuichi Kitagawa, Satoshi Wada, Takayuki Nakanishi, Koji Fushimi, Tomohiro Seki, Hajime Ito, Takeshi Iwasa, Tetsuya Taketsugu, Masayuki Gon, Kazuo Tanaka, Yoshiki Chujo, Shingo Hattori, Masanobu Karasawa, Kazuyuki Ishii
    ChemComm 54 10695 - 10697 2018年08月 [査読有り][招待有り]
  • Takuro Tsutsumi, Yu Harabuchi, Rina Yamamoto, Satoshi Maeda, Tetsuya Taketsugu
    Chemical Physics 515 564 - 571 2018年08月 [査読有り][招待有り]
  • Yang Cao, Phornphimon Maitarad, Min Gao, Tetsuya Taketsugu, Hongrui Li, Tingting Yan, Liyi Shi, Dengsong Zhang
    Applied Catalysis B: Environmental 238 51 - 60 2018年07月 [査読有り][通常論文]
  • Ken Sakaushi, Markus Eckardt, Andrey Lyalin, Tetsuya Taketsugu, R. Jurgen Behm, Kohei Uosaki
    ACS Catalysis 8 8162 - 8176 American Chemical Society ({ACS}) 2018年07月 [査読有り][通常論文]
  • Takuro Tsutsumi, Yuriko Ono, Zin Arai, Tetsuya Taketsugu
    Journal of Chemical Theory and Computation 14 4263 - 4270 American Chemical Society ({ACS}) 2018年07月 [査読有り][通常論文]
  • Yusuke Kondo, Masato Kobayashi, Tomoko Akama, Takeshi Noro, Tetsuya Taketsugu
    Journal of Computational Chemistry 39 16 964 - 972 2018年06月15日 [査読有り][通常論文]
     
    Ab initio all-electron computations have been carried out for Ce+ and CeF, including the electron correlation, scalar relativistic, and spin–orbit coupling effects in a quantitative manner. First, the n-electron valence state second-order multireference perturbation theory (NEVPT2) and spin–orbit configuration interaction (SOCI) based on the state-averaged restricted active space multiconfigurational self-consistent field (SA-RASSCF) and state-averaged complete active space multiconfigurational self-consistent field (SA-CASSCF) wavefunctions have been applied to evaluations of the low-lying energy levels of Ce+ with [Xe]4f15d16s1 and [Xe]4f15d2 configurations, to test the accuracy of several all-electron relativistic basis sets. It is shown that the mixing of quartet and doublet states is essential to reproduce the excitation energies. Then, SA-RASSCF(CASSCF)/NEVPT2 + SOCI computations with the Sapporo(-DKH3)-2012-QZP basis set were carried out to determine the energy levels of the low-lying electronic states of CeF. The calculated excitation energies, bond length, and vibrational frequency are shown to be in good agreement with the available experimental data. © 2018 Wiley Periodicals, Inc.
  • Masato Kobayashi, Toshikazu Fujimori, Tetsuya Taketsugu
    Journal of Computational Chemistry 39 15 909 - 916 2018年06月05日 [査読有り][通常論文]
     
    In linear-scaling divide-and-conquer (DC) electronic structure calculations, a buffer region is used to control the error introduced by the DC approximation. In this study, an energy-based error estimation scheme is proposed for the DC self-consistent field method with a two-layer buffer region scheme. Based on this scheme, a procedure to automatically determine the appropriate buffer region in the DC method is proposed. It was confirmed that the present method works satisfactorily in calculations of water clusters and proteins, although its performance was insufficient for the calculation of a delocalized graphene system. © 2018 Wiley Periodicals, Inc.
  • Andrey Lyalin, Vladimir G. Kuznetsov, Akira Nakayama, Igor V. Abarenkov, Ilya I. Tupitsyn, Igor E. Gabis, Kohei Uosaki, Tetsuya Taketsugu
    Journal of Physical Chemistry C 122 20 11096 - 11108 2018年05月24日 [査読有り][通常論文]
     
    Because of its exceptional lithium storage capacity, silicon is considered as a promising candidate for anode material in lithium-ion batteries (LIBs). In the present work, we demonstrate that methods of soft X-ray emission spectroscopy can be used as a powerful tool for the comprehensive analysis of the electronic and structural properties of lithium silicides LixSi forming in LIB's anode upon Si lithiation. On the basis of density functional theory and molecular dynamics simulations, it is shown that the coordination number of Si atoms in LixSi decreases with an increase in Li concentration both for the crystalline and amorphous phases. In amorphous a-LixSi alloys, Si tends to cluster, forming Si-Si covalent bonds even at the high lithium concentration. It is demonstrated that the Si-L2,3 emission bands of the crystalline and amorphous LixSi alloys show different spectral dependencies, reflecting the process of disintegration of Si-Si network into Si clusters and chains of the different sizes upon Si lithiation. The Si-L2,3 emission bands of LixSi alloys become narrower and shift toward higher energies with an increase in Li concentration. The shape of the emission band depends on the relative contribution of the X-ray radiation from the Si atoms having different coordination numbers. This feature of the Si-L2,3 spectra of LixSi alloys can be used for the detailed analysis of the Si lithiation process and LIB's anode structure identification.
  • Raman K. Singh, Takeshi Iwasa, Tetsuya Taketsugu
    Journal of Computational Chemistry 39 1878 - 1889 2018年05月 [査読有り][通常論文]
  • Andrey Lyalin, Kohei Uosaki, Tetsuya Taketsugu
    Electrocatalysis 9 2 182 - 188 2018年03月01日 [査読有り][通常論文]
     
    The catalytic activity for the oxygen reduction reaction (ORR) of a hexagonal boron nitride (h-BN) monolayer deposited on a Au(111) surface and decorated by a small planar Au8 cluster has been studied theoretically using density-functional theory. It is shown that gold nanoparticles (Au-NP) deposited on the h-BN/Au(111) surface can provide catalytically active sites for effective ORR at the perimeter interface with the support. Stabilization of oxygen at the perimeter interface between Au-NP and h-BN/Au(111) support promotes OOH* dissociation opening effective 4-electron pathway of ORR with formation of H2O. It is suggested that increase in the perimeter interface area between the supported Au-NP and the surface would result in increase of the ORR activity. Such increase in the perimeter interface area can be achieved by decreasing the size of Au-NP. Our calculations demonstrate the principal ability to functionalize inert materials such as stand-alone h-BN monolayer or Au surface for the ORR and open new way to design effective Pt-free catalysts for fuel cell technology. [Figure not available: see fulltext.].
  • Masanori Ebina, Takeshi Iwasa, Yu Harabuchi, Tetsuya Taketsugu
    The Journal of Physical Chemistry C 122 7 4097 - 4104 American Chemical Society ({ACS}) 2018年02月22日 [査読有り][通常論文]
     
    Gold-thiolate clusters of [Au25(SR)18]- are known to show multiple photoluminescence below and above 2.0 eV. Although recent theoretical studies have clarified the lowest energy emission from the S1 state originating from the Au13 core, the relaxation mechanism responsible for the higher-energy emissions remains unclear. Here, we present a theoretical study on the higher low-lying excited states of [Au25(SR)18]- (R = Me, EtPh: methyl, phenylethyl) using time-dependent density functional theory computations to gain further insights. In particular, we focused on the S7 state because there is a large energy gap between S6 and S7 at the ground state geometry. Two minimum structures that are found for the S7 state of [Au25(SMe)18]- show different natures, namely, the Au sp-intraband and d-sp interband transitions. The intraband excited state has an energy close to the lower excited state, whereas the interband excited state has a substantial energy gap. Considering the underestimation of the excitation energy, the calculated emission energy originating from the S7 interband excited state is reasonably assigned to the highest-energy emission.
  • Yuriko Ono, Kiyoshi Yagi, Toshiyuki Takayanagi, Tetsuya Taketsugu
    Physical Chemistry Chemical Physics 20 5 3296 - 3302 2018年02月07日 [査読有り][招待有り]
     
    Anharmonic vibrational state calculations were performed for PtCO and Ar-PtCO via the direct vibrational configuration interaction (VCI) method based on CCSD(T) energies and CCSD dipole moments at tens of thousands of grids, to get insights into the anomalous effect of a solid argon matrix on the vibrational spectra of PtCO. It was shown that, through the binding of Ar to PtCO via a strong van der Waals interaction, the Pt-C-O bending fundamental level drastically loses the infrared intensity although the corresponding overtone band shows a relatively large intensity. The origin of this phenomenon was analyzed based on the dipole moment surfaces and electron densities around the equilibrium structure. The present computations have solved the inconsistency between the gas-phase and the matrix-isolation experiments for PtCO.
  • Ayako Furuhama, Takashi Imamura, Satoshi Maeda, Tetsuya Taketsugu
    Chemical Physics Letters 692 111 - 116 2018年01月16日 [査読有り][通常論文]
     
    We performed a systematic reaction path search for the initial reactions of methyl amine with ozone (O3) in gas phase, by using a single-component artificial force induced reaction (SC-AFIR) method. The reaction rate constants calculated by UCCSD(T) energies and UM062X frequencies, agreed well with the experimental observation. This agreement could support the proposed reaction pathway for H-abstraction from amine as an initial step. The high rate constant for the reaction of trimethyl amine with O3 could be explained by a formation of the cyclic transition state structure.
  • Kenta Kokado, Takashi Machida, Takeshi Iwasa, Tetsuya Taketsugu, Kazuki Sada
    The Journal of Physical Chemistry C 122 1 245 - 251 American Chemical Society ({ACS}) 2018年01月11日 [査読有り][通常論文]
     
    Aggregation-induced emission (AIE) has emerged as a new class of attractive photoluminescence behavior. Understanding the precise mechanism of the AIE phenomenon will lead to the rational molecular design of novel molecules with AIE properties (AIEgens). In this work, we selected disubstituted derivatives of tetraphenylethene (TPE), a well-known archetypal AIEgen, as the model compounds to elucidate the AIE mechanism. As the result of photochemical experiments and quantum chemical computations, π-bond twist (π twist), including E-Z isomerization (EZI), was found to be the major factor for quenching the photoexcited state of TPE derivatives in the solution state, differently from the well-accepted propeller-like rotation of the side phenyl groups in earlier research. In photochemical experiments, the prepared TPE derivatives exhibited EZI in the solution state upon photoirradiation, and a negative correlation was observed between this isomerization and the AIE phenomenon. The theoretical computations verified the crucial role of π twist triggered by photoirradiation in the solution state, rather than intramolecular rotation. In the crystal state, π twist was efficiently suppressed by the surrounding molecules. Our results will support the realization of novel smart AIEgens that can respond to various external stimuli.
  • Kinoshita, Shin-nosuke, Kinoshita, Shin-nosuke, Miyazaki, Yasunori, Miyazaki, Yasunori, Sumida, Masataka, Sumida, Masataka, Onitsuka, Yuuki, Onitsuka, Yuuki, Kohguchi, Hiroshi, Kohguchi, Hiroshi, Inokuchi, Yoshiya, Inokuchi, Yoshiya, Akai, Nobuyuki, Akai, Nobuyuki, Shiraogawa, Takafumi, Shiraogawa, Takafumi, Ehara, Masahiro, Ehara, Masahiro, Yamazaki, Kaoru, Yamazaki, Kaoru, Harabuchi, Yu, Harabuchi, Yu, Maeda, Satoshi, Maeda, Satoshi, Taketsugu, Tetsuya, Taketsugu, Tetsuya, Ebata, Takayuki, Ebata, Takayuki
    Physical Chemistry Chemical Physics 20 17583 - 17598 2018年 [査読有り][通常論文]
  • Takuro Tsutsumi, Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    Physical Chemistry Chemical Physics 20 3 1364 - 1372 2018年 [査読有り][通常論文]
     
    A methodology to analyze a trajectory on-the-fly (TOF) based on a global reaction route map consisting of intrinsic reaction coordinate (IRC) pathways is proposed. By using the distance functions in the configurational space, the location of each point on the trajectories is detected, providing a dynamical picture that the molecular system goes over several minima and transition states in the reaction path network. In its application to structural transformations of an Au5 cluster, a variety of reaction routes are obtained, and the hopping from one IRC to another IRC (IRC-jump) is analyzed. The branching of trajectories over many minima on the potential energy surface via valley-ridge transition points is also discussed.
  • Yoshiaki Nishijima, Shogo Shimizu, Keisuke Kurihara, Yoshikazu Hashimoto, Hajime Takahashi, Armandas Balcytis, Gediminas Seniutinas, Shinji Okazaki, Jurga Juodkazyte, Takeshi Iwasa, Tetsuya Taketsugu, Yoriko Tominaga, Saulius Juodkazis
    OPTICS EXPRESS 25 20 24081 - 24092 2017年10月 [査読有り][通常論文]
     
    For hydrogen sensor and storage applications, films of Au and Pd were (i) co-sputtered at different rates or (ii) deposited in a sequentially alternating fashion to create a layered structure on a cover glass. Peculiarities of hydrogen uptake and release were optically monitored using 1.3 mu m wavelength light. Increase of optical transmission was observed for hydrogenated Pd-rich films of 10-30 nm thickness. Up to a three times slower hydrogen release took place as compared with the hydrogen uptake. Compositional ratio of Au: Pd and thermal treatment of films provided control over the optical extinction changes and hydrogen uptake/ release time constants. Higher uptake and release rates were observed in the annealed Au: Pd films as compared to those deposited at room temperature and were faster for the Au-richer films. Three main parameters relevant for sensors: sensitivity, selectivity, stability (reproducibility) are discussed together with the hydrogenation mechanism in Au: Pd alloys. (C) 2017 Optical Society of America
  • Kei Yanagisawa, Yuichi Kitagawa, Takayuki Nakanishi, Tomoko Akama, Masato Kobayashi, Tomohiro Seki, Koji Fushimi, Hajime Ito, Tetsuya Taketsugu, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2017 32 3843 - 3848 2017年09月 [査読有り][招待有り]
     
    Luminescent mononuclear seven-coordinate Eu-III complexes, with monocapped-octahedral (point group: C-3v), monocapped-trigonal-prismatic (C-2v), and pentagonal-bipyramidal (D-5h) coordination structures, are reported. The complexes each consist of a Eu-III ion, three tetramethylheptanedionates, and a phosphine oxide derivative. Controlling steric hindrance by means of introducing methyl groups into the phosphine oxide ligands resulted in the formation of three types of coordination polyhedral structures. The coordination geometrical structures of the Eu-III complexes were evaluated by single-crystal X-ray diffraction analysis and shape-factor calculations. The radiative rate constant of the Eu-III complex with a monocapped-octahedral structure was larger than those with monocapped-trigonal-prismatic and pentagonal-bipyramidal structures. Characteristic photophysical properties of the seven-coordinate Eu-III complexes are discussed with TD-DFT calculations and Arrhenius analysis of the ligand-to-metal charge transfer.
  • Xiaowei Song, Matias R. Fagiani, Sreekanta Debnath, Min Gao, Satoshi Maeda, Tetsuya Taketsugu, Sandy Gewinner, Wieland Schoellkopf, Knut R. Asmis, Andrey Lyalin
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 34 23154 - 23161 2017年09月 [査読有り][通常論文]
     
    The mechanism of dissociative D-2 adsorption on Ti2O4-, which serves as a model for an oxygen vacancy on a titania surface, is studied using infrared photodissociation spectroscopy in combination with density functional theory calculations and a recently developed single-component artificial force induced reaction method. Ti2O4- readily reacts with D-2 under multiple collision conditions in a gas-filled ion trap held at 16 K forming a global minimum-energy structure (DO-Ti-(O)(2)-Ti(D)-O)(-). The highly exergonic reaction proceeds quasi barrier-free via several intermediate species, involving heterolytic D-2-bond cleavage followed by D-atom migration. We show that, compared to neutral Ti2O4, the excess negative charge in Ti2O4- is responsible for the substantial lowering of the D-2 dissociation barrier, but does not affect the molecular D-2 adsorption energy in the initial physisorption step.
  • Xue-fang Yu, Shohei Yamazaki, Tetsuya Taketsugu
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 34 23289 - 23301 2017年09月 [査読有り][通常論文]
     
    Solvent effects on the excited-state double proton transfer (ESDPT) mechanism in the 7-azaindole (7AI) dimer were investigated using the time-dependent density functional theory (TDDFT) method. Excited-state potential energy profiles along the reaction paths in a locally excited (LE) state and a charge transfer (CT) state were calculated using the polarizable continuum model (PCM) to include the solvent effect. A series of non-polar and polar solvents with different dielectric constants were used to examine the polarity effect on the ESDPT mechanism. The present results suggest that in a non-polar solvent and a polar solvent with a small dielectric constant, ESDPT follows a concerted mechanism, similar to the case in the gas phase. In a polar solvent with a relatively large dielectric constant, however, ESDPT is likely to follow a stepwise mechanism via a stable zwitterionic intermediate in the LE state on the adiabatic potential energy surface, although inclusion of zero-point vibrational energy (ZPE) corrections again suggests the concerted mechanism. In the meantime, the stepwise reaction path involving the CT state with neutral intermediates is also examined, and is found to be less competitive than the concerted or stepwise path in the LE state in both non-polar and polar solvents. The present study provides a new insight into the experimental controversy of the ESDPT mechanism of the 7AI dimer in a solution.
  • Eiji Yamamoto, Satoshi Maedab, Tetsuya Taketsugub, Hajime Ito
    SYNLETT 28 11 1258 - 1267 2017年07月 [査読有り][通常論文]
     
    Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe2Si-B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This borylation reaction is further applied to the first direct dimesitylboryl (BMes(2)) substitution of aryl halides using Ph2MeSi-BMes(2) and Na(O-t-Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials. 1 Introduction 2 Boryl Substitution of Organohalides with PhMe2Si-B(pin)/Alkoxy Bases 3 Mechanistic Investigations 4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method 5 Dimesitylboryl Substitution of Aryl Halides with Ph2MeSi-BMes(2)/Na(O-t-Bu) 6 Conclusion
  • Ryohei Uematsu, Chihiro Saka, Yosuke Sumiya, Tomoya Ichino, Tetsuya Taketsugu, Satoshi Maeda
    CHEMICAL COMMUNICATIONS 53 53 7302 - 7305 2017年07月 [査読有り][通常論文]
     
    An autocatalytic cycle was found in the mechanism of autoxidation of triethylborane using density functional theory calculations. The reaction starts with the generation of an ethyl radical via slow homolytic substitution. Fast radical propagation then takes place through a catalytic cycle in which the ethyl radical acts as a catalyst.
  • Takayoshi Yoshimura, Satoshi Maeda, Tetsuya Taketsugu, Masaya Sawamura, Keiji Morokuma, Seiji Mori
    CHEMICAL SCIENCE 8 6 4475 - 4488 2017年06月 [査読有り][通常論文]
     
    We explored the reaction mechanism of the cationic rhodium(I)-BINAP complex catalysed isomerisation of allylic amines using the artificial force induced reaction method with the global reaction route mapping strategy, which enabled us to search for various reaction paths without assumption of transition states. The entire reaction network was reproduced in the form of a graph, and reasonable paths were selected from the complicated network using Prim's algorithm. As a result, a new dissociative reaction mechanism was proposed. Our comprehensive reaction path search provided rationales for the E/Z and S/R selectivities of the stereoselective reaction.
  • Makito Takagi, Tetsuya Taketsugu, Hiori Kino, Yoshitaka Tateyama, Kiyoyuki Terakura, Satoshi Maeda
    PHYSICAL REVIEW B 95 18 184110  2017年05月 [査読有り][通常論文]
     
    We propose an approach to perform the global search for low-lying crystal structures from first principles, by combining the artificial force induced reaction (AFIR) method and the periodic boundary conditions (PBCs). The AFIR method has been applied extensively to molecular systems to elucidate the mechanism of chemical reactions such as homogeneous catalysis. The present PBC/AFIR approach found 274 local minima for carbon crystals in the C-8 unit cell described by the generalized gradient approximation-Perdew-Burke-Ernzerhof functional. Among many newly predicted structures, three low-lying structures, which exhibit somewhat higher energy compared with those previously predicted, such as Cco-C-8 (Z-carbon) and M-carbon, are further discussed with calculations of phonon and band dispersion curves. Furthermore, approaches to systematically explore two- or one-dimensional periodic structures are proposed and applied to the C-8 unit cell with the slab model. These results suggest that the present approach is highly promising for predicting crystal structures.
  • Tomohiro Seki, Noriaki Tokodai, Shun Omagari, Takayuki Nakanishi, Yasuchika Hasegawa, Takeshi Iwasa, Tetsuya Taketsugu, Hajime Ito
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 139 19 6514 - 6517 2017年05月 [査読有り][通常論文]
     
    Upon mechanical stimulation, 9-anthryl gold(I) isocyanide complex 3 exhibited a bathochromic shift of its emission color from the visible to the infrared (IR) region, which is unprecedented in its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs 3 alpha and 3 beta exhibit emission wavelength maxima (lambda(em,max)) at 448 and 710 nm, respectively. Upon grinding, the lambda(em,max) of 3 alpha(ground) and 3 beta(ground) are bathochromically shifted to 900 nm, i.e., Delta lambda(em,max) (3 alpha) = 452 nm or 1.39 eV. Polymorphs 3 alpha and 3 beta thus represent the first examples of mechanochromic luminescent materials with lambda(em,max) in the IR region.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    CHEMICAL PHYSICS LETTERS 674 141 - 145 2017年04月 [査読有り][通常論文]
     
    We report a new approach to search for structures of minimum energy conical intersection (MECIs) automatically. Gradient projection (GP) method and single component artificial force induced reaction (SC-AFIR) method were combined in the present approach. As case studies, MECIs of benzene and naphthalene between their ground and first excited singlet electronic states (S-0/S-1-MECIs) were explored. All S-0/S-1-MECIs reported previously were obtained automatically. Furthermore, the number of force calculations was reduced compared to the one required in the previous search. Improved convergence in a step in which various geometrical displacements are induced by SC-AFIR would contribute to the cost reduction. (C) 2017 Elsevier B.V. All rights reserved.
  • Min Gao, Daisuke Horita, Yuriko Ono, Andrey Lyalin, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 121 5 2661 - 2668 2017年02月 [査読有り][招待有り]
     
    A systematic investigation is performed on structural transformations in small neutral gold clusters (Au-3-Au-12) induced by O-2 adsorption, with the use of the fully automated reaction path search techniques, i.e., anharrnonic downward distortion following (APDF) and artificial force induced reaction (AFIR) methods, implemented in the global reaction route mapping (GRRM) program. For each size of Au cluster, the most stable structure, low-energy isomers, and a network of isomerization pathways are determined. The located Au-n-O-2 adsorption forms can be classified into two groups: eta(1)-AunO2, where only one oxygen atom is adsorbed on Au-n, and eta(2)=AunO2, where both oxygen atoms are adsorbed on Au-n in a hridged manner. These two adsorption forms can be transformed to eath other with a low barrier. The isornerization pathways of gold clusters upon O-2 adsorption are compared with those obtained for the pure gold cluSters Without O-2. It is demonstrated that O-2 adsorption promotes structural transformations in gold clusters considerably by lowering the isomerization battlers. The presence of the unpaired electron is a necessary condition for O-2 adsorption in the eta(1)-Au O-2 form, as well as the subsequent cluster isomerization and the O-O bond activation. These conclusions ate consistent with the recent experimental resits by Fielicke et al.
  • Andrey Lyalin, Ken-ichi Shimizu, Tetsuya Taketsugu
    The Journal of Physical Chemistry C 121 6 3488 - 3495 American Chemical Society ({ACS}) 2017年02月 [査読有り][通常論文]
     
    We present results of theoretical investigation on catalytic hydrogen elimination from isopropanol (C3H8O) by free and (theta-Al2O3(010)-supported Ni-13 cluster. The specific role played by the perimeter interface between the nickel cluster and alumina support is discussed. It is demonstrated that dehydrogenation of C3H8O on the free Ni-13 cluster is a two-step process with the first hydrogen elimination from the alcohol hydroxyl group, followed by C-H bond cleavage. Our calculations show that H elimination from OH group of C3H8O to Ni-13 cluster is the rate-determining step with the barrier of 0.95 eV, while the C-H bond cleavage requires overcoming the barrier of 0.41 eV. In the case of Ni-13 cluster supported on (theta-Al2O3(010) the isopropanol molecule adsorbs on top of the surface Al atom in the close vicinity of the nickel cluster, which results in considerable decrease in barrier for H elimination due to formation of the complementary adsorption sites at the metal/support interface. It is demonstrated that intermediate formation of the Ni-C bond considerably promotes C-H bond cleavage. The described mechanism provides fundamental understanding of the process of the oxidant-free catalytic hydrogen elimination from alcohols on supported nickel clusters and can serve as a tool for rational design of novel type of nanocatalysts based on abundant noble-metal-free materials.
  • Ken Sakaushi, Andrey Lyalin, Satoshi Tominaka, Tetsuya Taketsugu, Kohei Uosaki
    ACS NANO 11 2 1770 - 1779 2017年02月 [査読有り][通常論文]
     
    The material choice for efficient electrocatalysts is limited because it is necessary to be highly active as well as highly stable. One direction to solve this issue is to understand elementary steps of electrode processes and build an unconventional strategy for a conversion of inert and, therefore, stable materials into efficient catalysts. Herein, we propose a simple concept for obtaining catalysts from inert and hence stable materials by forming their heterojunctions, namely, covering inert Au with corrugated carbon nitrogen-based two-dimensional porous frameworks. It shows more than 10 times better activity for the hydrogen evolution reaction than for the pure Au surface, and it also demonstrates the high catalytic activity for the oxygen reduction reaction (ORR) via an effective four-electron reduction mechanism, which is different from the usual two electron reduction typical for ORR on Au surfaces. This activity induced by formation of a heterojunction was analyzed by a conjugation of computational and experimental methods and found to originate from alternative efficient reaction pathways that emerged by the corrugated porous framework and the Au surface. This work provides not only the method for creating active surface but also the knowledge on elementary steps of such complicated multielectron transfer reactions, thereby leading to intriguing strategies for developing energy conversion reactions based on materials which had never been considered as catalysts before.
  • Majharul Haque Khan, Sina S. Jamali, Andrey Lyalin, Paul J. Molino, Lei Jiang, Hua Kun Liu, Tetsuya Taketsugu, Zhenguo Huang
    ADVANCED MATERIALS 29 4 1603937  2017年01月 [査読有り][通常論文]
     
    Outstanding protection of Cubyhigh-quality boron nitridenano film (B N N F) 1-2 atomic layers thick in salt water is observed, while defective BNNF accelerates the reaction of Cu toward water. The chemical stability, insulating nature, and impermeability of ions through the BN hexagons render BNNF a great choice for atomic-scale protection.
  • Yosuke Sumiya, Tetsuya Taketsugu, Satoshi Maeda
    JOURNAL OF COMPUTATIONAL CHEMISTRY 38 2 101 - 109 2017年01月 [査読有り][通常論文]
     
    The branching ratio of unimolecular decomposition can be evaluated by solving the rate equations. Recent advances in automated reaction path search methods have enabled efficient construction of the rate equations based on quantum chemical calculations. However, it is still difficult to solve the rate equations composed of hundreds or more elementary steps. This problem is especially serious when elementary steps that occur in highly different timescales coexist. In this article, we introduce an efficient approach to obtain the branching ratio from a given set of rate equations. It has been derived from a recently proposed rate constant matrix contraction (RCMC) method, and termed full-RCMC (f-RCMC). The f-RCMC gives the branching ratio without solving the rate equations. Its performance was tested numerically for unimolecular decomposition of C3H5 and C4H5. Branching ratios obtained by the f-RCMC precisely reproduced the values obtained by numerically solving the rate equations. It took about 95 h to solve the rate equations of C4H5 consisting of 234 elementary steps. In contrast, the f-RCMC gave the branching ratio in less than 1 s. The f-RCMC would thus be an efficient alternative of the conventional kinetic simulation approach. (C) 2016 Wiley Periodicals, Inc.
  • Masato Kobayashi, Tetsuya Taketsugu
    CHEMISTRY LETTERS 45 11 1268 - 1270 2016年11月 [査読有り][通常論文]
     
    The Hartree-Fock-Bogoliubov (HFB) theory has recently attracted considerable attention in quantum chemistry as a novel strategy to account for the static electron correlation, which plays an essential role when breaking chemical bonds and treating diradical systems. The linear-scaling divide-and-conquer (DC) method is applied to the HFB method to treat large-scale bond-breaking and/or diradical systems with reasonable computational effort.
  • Harabuchi Y, Yamamoto R, Maeda S, Takeuchi S, Tahara T, Taketsugu T
    The Journal of Physical Chemistry A 120 44 8804 - 8812 2016年11月 [査読有り][通常論文]
     
    Ab initio molecular dynamics (AIMD) simulations were carried out for pi pi*-excited 1,1'-dimethylstilbene (dmSB) at the spin-flip time-dependent density functional theory (SF-TDDFT) level with the T-sF-index technique, to get insights into the substitution effects on the photoisomerization dynamics of stilbene (SB). It is found that the reaction path from the Franck-Condon structure of cis-dmSB is oriented toward the 4,4-dihydrophenanthrene (DHP) side from the beginning, which is in contrast to the case of SB where the pathway is oriented toward the twist side in the initial stage. The optimized geometries of minima and the minimum-energy conical intersection (MECI) suggested that molecules in the DHP region could easily decay to the ground state. On the other hand, S-1/S-0-MECI and S-1-minimum in the twist region have a relatively different geometry from each other, which is consistent with the experimental observation of the long lifetime of the perpendicular structure. AIMD simulations showed that more trajectories enter the well of the DHP side than the well of the twist side and that all of the trajectories going to the DHP side reached the S-1/S-0-CI region within similar to 0.2 ps on average, while very few trajectories reached S-1/ S-0-CI even after 1 ps in the twist region. Decrease in the S-1 population in the cis and twist regions qualitatively reproduced the temporal profiles of the transient absorption bands of dmSB observed in the visible and ultraviolet regions, respectively.
  • Takako Kudo, Tetsuya Taketsugu, Mark S. Gordon
    JOURNAL OF PHYSICAL CHEMISTRY A 120 43 8699 - 8715 2016年11月 [査読有り][招待有り]
     
    The mechanism and dynamics for the formation of a hydrogen molecule in the cavity of POSS (polyhedral oligomeric silsesquioxane) compounds have been investigated by ab initio molecular orbital and ab initio molecular dynamics (AIMD) methods. The host molecules are two POSS compounds, T-8 ([HSiO1.5](8)) (O-h) and T-12 ( [HSiO1.5](12)) (D-2d). To investigate the H-2 formation reaction, two approaches were considered: trajectories were initiated by inserting a second hydrogen atom into (I) a hydrogen molecule encapsulated-POSS (H + H-2@T-n -> (H + H-2)@T-n; n = 8, 12), and (II) the hydrogen atom and hydrogen molecule-encapsulated-POSS (H + (H + H-2)@T-n -> 2 H-2@T-n; n = 8 and 12). A wide variety of reactions were observed depending on the system and the initial conditions, especially in process II. Therefore, for reaction II, an energy decomposition analysis was employed to examine the variation of the distribution of the translational, rotational and vibrational kinetic energies of the guest species along the reaction processes, and to determine the role of each energy component for the H-2-formation. This analysis provides important insights into the expected kinetic energy distributions among the products of encapsulation reactions.
  • Satoshi Maeda, Yu Harabuchi, Makito Takagi, Tetsuya Taketsugu, Keiji Morokuma
    CHEMICAL RECORD 16 5 2232 - 2248 2016年10月 [査読有り][通常論文]
     
    In this account, a technical overview of the artificial force induced reaction (AFIR) method is presented. The AFIR method is one of the automated reaction-path search methods developed by the authors, and has been applied extensively to a variety of chemical reactions, such as organocatalysis, organometallic catalysis, and photoreactions. There are two modes in the AFIR method, i.e., a multicomponent mode and a single-component mode. The former has been applied to bimolecular and multicomponent reactions and the latter to unimolecular isomerization and dissociation reactions. Five numerical examples are presented for an Aldol reaction, a Claisen rearrangement, a Co-catalyzed hydroformylation, a fullerene structure search, and a nonradiative decay path search in an electronically excited naphthalene molecule. Finally, possible applications of the AFIR method are discussed.
  • Andrey Lyalin, Min Gao, Tetsuya Taketsugu
    CHEMICAL RECORD 16 5 2324 - 2337 2016年10月 [査読有り][招待有り]
     
    In this Personal Account, we review the work of our group in the area of environmental and energy-related nanocatalysis over the past seven years. We focus on understanding the fundamental mechanisms that control the properties of atomic clusters and nanoparticles - a form of matter that is intermediate between atoms and their bulk counterpart. The emphasis is on the theoretical design of effective catalysts based on cheap and abundant elements. The main idea that stands behind our work is that even catalytically inactive or completely inert materials can be functionalized at the nanoscale via the size, structure, morphology, and support effects. Such an approach opens up new ways to design catalytically active systems based on materials never before considered as catalysts. In particular, we demonstrate that hexagonal boron nitride (h-BN), which has been traditionally considered an inert material, can be functionalized and become active for a number of catalytic reactions involving oxygen activation, oxidation by molecular oxygen, and the oxygen reduction reaction.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 138 41 13481 - 13484 2016年10月 [査読有り][通常論文]
     
    Two theoretically designed and one experimentally reported pincer-type phosphorus compounds are found to be active for the hydrogenation of carbon dioxide with ammonia borane. DFT, ONIOM(CCSD-(T):MP2), and CCSD(T) computational results demonstrated that the reaction occurs through phosphorus ligand cooperative catalysis, which provides an unprecedented protocol for metal-free CO2 conversion. The phosphorus compounds with the NNN ligand are more active than those with the ONO ligand. The planar conjugate ligand considerably improves the efficiency of the catalyst.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    CHEMISTRY LETTERS 45 8 940 - 942 2016年08月 [査読有り][通常論文]
     
    Automated searches for minimum energy conical intersection structures between the lowest two singlet electronic states (S-0/S-1-MECIs) of furan and dibenzofuran were made. In total, eight and sixty S-0/S-1-MECIs were found for furan and dibenzofuran, respectively, around their Franck-Condon (FC) regions. The difference in their experimental fluorescence quantum yields was discussed based on the barrier heights to reach S-0/S-1-MECIs from the FC regions. It was found that the stability of the FC region is the major factor giving the difference in their fluorescence quantum yields.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    ACS CATALYSIS 6 8 4859 - 4870 2016年08月 [査読有り][通常論文]
     
    Catalysis of phosphorus compound 10-P-3(2)3,7-di(tert-butyl)-5-aza-2,8-dioxa-l-phosphabicyclo[3.3.0]octa-2,4,6-triene 1P and its analogues in transfer hydrogenation of azobenzene with ammonia-borane (NH3BH3) using DFT, CCSD(T), and ONIOM(CCSD(T):MP2) methods. Theoretical calculations clearly reveal that this transfer hydrogenation reaction occurs through the phosphorus ligand cooperative catalysis function with a change in the phosphorus oxidation state between +I and +III. It is noteworthy that the change in phosphorus oxidation state is a characteristic feature of the cooperative catalysis by 1P: it is not easy for a main -group element to change its oxidation state. This characteristic feature differs from that of metal ligand cooperative catalysis in which the metal oxidation state does not change. Theoretical calculations also disclose that the catalytic activity of IP-like compound is improved by introducing electron -withdrawing substituents to the ligand and using the conjugated planar framework of the ligand. The best catalyst here is predicted to be active for transfer hydrogenations of various ketones and acetaldehyde with NH3BH3, indicating that IP-like compound exhibit a wide application scope as a catalyst.
  • Kohei Uosaki, Ganesan Elumalai, Hung Cuong Dinh, Andrey Lyalin, Tetsuya Taketsugu, Hidenori Noguchi
    SCIENTIFIC REPORTS 6 32217  2016年08月 [査読有り][通常論文]
     
    It is demonstrated that electrochemical hydrogen evolution reaction ( HER) proceeds very efficiently at Au electrode, an inert substrate for HER, modified with BNNS, an insulator. This combination has been reported to be an efficient electrocatalyst for oxygen reduction reaction. Higher efficiency is achieved by using the size controlled BNNS (<1 mu m) for the modification and the highest efficiency is achieved at Au electrode modified with the smallest BNNS ( 0.1-0.22 mu m) used in this study where overpotentials are only 30 mV and 40 mV larger than those at Pt electrode, which is known to be the best electrode for HER, at 5 mAcm(-2) and at 15 mAcm(-2), respectively. Theoretical evaluation suggests that some of edge atoms provide energetically favored sites for adsorbed hydrogen, i.e., the intermediate state of HER. This study opens a new route to develop HER electrocatalysts.
  • Kenichiro Saita, Yu Harabuchi, Tetsuya Taketsugu, Osamu Ishitani, Satoshi Maeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 26 17557 - 17564 2016年07月 [査読有り][通常論文]
     
    The mechanism of the CO ligand dissociation of fac-[Re-I(bpy)(CO)(3)P(OMe)(3)](+) has theoretically been investigated, as the dominant process of the photochemical ligand substitution (PLS) reactions of fac-[Re-I(bpy)(CO)(3)PR3](+), by using the (TD-)DFT method. The PLS reactivity can be determined by the topology of the T-1 potential energy surface because the photoexcited complex is able to decay into the T-1 state by internal conversions (through conical intersections) and intersystem crossings (via crossing seams) with sufficiently low energy barriers. The T-1 state has a character of the metal-to-ligand charge-transfer ((MLCT)-M-3) around the Franck-Condon region, and it changes to the metal-centered ((MC)-M-3) state as the Re-CO bond is elongated and bent. The equatorial CO ligand has a much higher energy barrier to leave than that of the axial CO, so that the axial CO ligand selectively dissociates in the PLS reaction. The single-component artificial force induced reaction (SC-AFIR) search reveals the CO dissociation pathway in photostable fac-[ReI(bpy)(CO)(3)Cl]; however, the dissociation barrier on the T-1 state is substantially higher than that in fac-[ReI(bpy)(CO)(3)PR3](+) and the minimum-energy seams of crossings (MESXs) are located before and below the barrier. The MESXs have also been searched in fac-[Re-I(bpy)(CO)(3)PR3](+) and no MESXs were found before and below the barrier.
  • Min Gao, Masashi Adachi, Andrey Lyalin, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 15993 - 16001 2016年07月 [査読有り][招待有り]
     
    Adsorption and catalytic activation of the molecular oxygen on the hexagonal boron nitride (h-BN) monolayer doped with carbon atom have been studied theoretically using density functional theory. It is demonstrated that C doping in B position of h-BN (C-B@h-BN) produces n-type semiconductor BN material with noticeable catalytic activity for O-2 activation in the large area extended far away from the C impurity. The adsorption energy of O2 on CB@h-BN decreasing slowly with the increase in distance from the CB defect, while O2 remains highly activated. No such effect is observed for monolayer h-BN doped with different atoms of group III, IV and V and transition-metal elements, such as B, N, Al, Si, Ge, Ni, Pt, Pd, and Au, where O-2 adsorbs only in the close vicinity of the dopant. It is shown that even small concentration of C dopants can functionalize the large surface area of monolayer BN making it promising catalytic material for oxygen activation and oxygen reduction reaction.
  • Kotaro Shimada, Atsushi Kobayashi, Yuriko Ono, Hiroki Ohara, Tatsuya Hasegawa, Tetsuya Taketsugu, Eri Sakuda, Soichiro Akagi, Noboru Kitamura, Masako Kato
    JOURNAL OF PHYSICAL CHEMISTRY C 120 29 16002 - 16011 2016年07月 [査読有り][招待有り]
     
    Thiolato-bridged dinuclear, tetranuclear, and hexanuclear Cu(I) complexes [Cu-2(P boolean AND S)(2)(PPh3)(2)], [Cu-4(P boolean AND S)(4)(CH3CN)(2)], and [Cu-6(P boolean AND S)(6)] (abbreviated as Cu-2, Cu-4, and Cu-6, respectively, P boolean AND S = 2-(diphenylphosphino)benzenethiolate, PPh3 = triphenylphosphine) were synthesized and characterized by elemental analyses and single-crystal X-ray diffraction measurements. These complexes had {Cu2S2}, {Cu4S4}, and {Cu6S6} cluster cores and exhibited strong luminescence at room temperature in solid states. Different luminescence properties were observed depending on the core structure. Cu-2, Cu-4, and Cu-6 exhibited blue-green (lambda(max) = 482 nm, Phi(em) = 0.52), green (lambda(max) = 526 nm, Phi(em) = 0.19), and yellow (lambda(max) = 553 nm, Phi(em) = 0.49) luminescence, respectively, at 298 K in the solid state; among them, only Cu6 showed luminescence thermochromism. Different radiative rate constants at room temperature and 78 K derived from the emission lifetimes and quantum yields indicate that the luminescence from Cu-2 and Cu-4 at room temperature originated from thermally activated delayed fluorescence (TADF), whereas the luminescence at low temperatures was attributed to the phosphorescence. The temperature dependence of the emission lifetimes was successfully analyzed by the singlettriplet two-state model with an energy difference (Delta ES1-T1) of 547 and 775 cm(-1) for Cu-2 and Cu-4, respectively. Based on the time-dependent density-functional theory calculations, the origin of the luminescence for Cu-2 and Cu-4 was attributed to the charge transfer from the cluster core to the ligand. Moreover, the small values of Delta ES1-T1 for Cu-2 and Cu-4 were supported by the excited state calculations. On the other hand, the emission origin of Cu-6 was attributed to the phosphorescence from the triplet cluster-centered (3CC) excited state in which the electron is located on a bonding in-phase orbital constructed from the 4s/4p orbitals of the Cu atoms because only Cu6 contains trigonal-planar Cu(I) ions in the cluster.
  • Ganesan Elumalai, Hidenori Noguchi, Andrey Lyalin, Tetsuya Taketsugu, Kohei Uosaki
    ELECTROCHEMISTRY COMMUNICATIONS 66 53 - 57 2016年05月 [査読有り][通常論文]
     
    Overpotential for oxygen reduction reaction (ORR) at Au electrode is reported to be reduced by 0.27 V by the modification with boron nitride nanosheet (BNNS) but oxygen is reduced only to H2O2 by 2-electron process at Au electrode. Here we demonstrate that the decoration of BNNS with gold nanoparticles (AuNP) not only reduces the overpotential for ORR further by ca. 50 mV, but also opens a 4-electron reduction route to water. Both rotating disk electrode experiments with Koutecky-Levich analysis and rotating ring disk electrode measurements show that more than 50% of oxygen is reduced to water via 4-electron process at Au-BNNS/Au electrode while less than 20 and 10% of oxygen are reduced to water at the BNNS/Au and bare Au electrodes, respectively. Theoretical analysis of free energy profiles for ORR at the BN monolayer with and without Au-8 cluster placed on Au(111) shows significant stabilization of adsorbed oxygen atom by the Au-8 cluster, opening a 4-electron reduction pathway. (C) 2016 Elsevier B.V. All rights reserved.
  • Yu Harabuchi, Julien Eng, Etienne Gindensperger, Tetsuya Taketsugu, Satoshi Maeda, Chantal Daniel
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 12 5 2335 - 2345 2016年05月 [査読有り][通常論文]
     
    The mechanism of ultrafast intersystem crossing in rhenium(I) carbonyl bipyridine halide complexes Re(X)(CO)(3)(bpy) (X = Cl, Br, I) is studied by exploring the structural deformations when going from Franck-Condon (FC) to critical geometries in the low-lying singlet and triplet excited states and by selecting the key vibrational modes. The luminescent decay observed in [Re(Br)(CO)(3)(bpy)] is investigated by means of wavepacket propagations.based on the multiconfiguration time-dependent Hartree (MCTDH) method. The dominant coordinates underlying the nonradiative decay process are extracted from minima, minimum energy seam of crossing (MESX) and minimum energy conical intersection (MECI) geometries obtained by the seam model function (SME)/Single-component artificial force induced reaction (SC-AFIR) approach. By choosing the normal modes used in MCTDH from the MECI and MESX geometries, not only the degenerate energy points but also the low-energy-gap regions are included. For this purpose a careful vibrational analysis is performed at each critical geometry and analyzed under the light of the pertinent nonadiabatic coupling terms obtained from the linear vibronic coupling (LVC) model augmented by spin orbit coupling (SOC) in the electronic diabatic representation.
  • Yuriko Ono, Yusuke Kondo, Masato Kobayashi, Tetsuya Taketsugu
    CHEMISTRY LETTERS 45 4 478 - 480 2016年04月 [査読有り][通常論文]
     
    It was demonstrated that spin-orbit coupling changed the lowest-lying electronic states of PtCN and PtNC from (2)Sigma to (2)Delta(5/2)d by highly correlated electronic structure theory, considering relativistic effects. On the other hand, the electronic ground states of PdCN and PdNC remained (2)Sigma(1/2), even after considering spin-orbit coupling effects.
  • Yutaka Nagahata, Satoshi Maeda, Hiroshi Teramoto, Takashi Horiyama, Tetsuya Taketsugu, Tamiki Komatsuzaki
    JOURNAL OF PHYSICAL CHEMISTRY B 120 8 1961 - 1971 2016年03月 [査読有り][通常論文]
     
    Markovian dynamics on complex reaction networks are one of the most intriguing subjects in a wide range of research fields including chemical reactions, biological physics, and ecology. To represent the global kinetics from one node (corresponding to a basin on an energy landscape) to another requires information on multiple pathways that directly or indirectly connect these two nodes through the entire network. In this paper we present a scheme to extract a hierarchical set of global transition states (TSs) over a discrete time Markov chain derived from first-order rate equations. The TSs can naturally take into account the multiple pathways connecting any pair of nodes. We also propose a new type of disconnectivity graph (DG) to capture the hierarchical organization of different time scales of reactions that can capture changes in the network due to changes in the observation. The crux is the introduction of the minimum conductance cut (MCC) in graph clustering, corresponding to the dividing surface across the network having the "smallest" transition probability between two disjoint subnetworks (superbasins on the energy landscape) in the network. We present a new combinatorial search algorithm for finding this MCC. We apply our method to a reaction network of Claisen rearrangement of allyl vinyl ether that consists of 23 nodes and 66 links (saddles on the energy landscape) connecting them. We compare the kinetic properties of our DG to those of the transition matrix of the rate equations and show that our graph can properly reveal the hierarchical, organization of time scales in a network.
  • Takeshi Iwasa, Masato Takenaka, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 144 12 124116  2016年03月 [査読有り][通常論文]
     
    A theoretical method to compute infrared absorption spectra when a molecule is interacting with an arbitrary nonuniform electric field such as near-fields is developed and numerically applied to simple model systems. The method is based on the multipolar Hamiltonian where the light-matter interaction is described by a spatial integral of the inner product of the molecular polarization and applied electric field. The computation scheme is developed under the harmonic approximation for the molecular vibrations and the framework of modern electronic structure calculations such as the density functional theory. Infrared reflection absorption and near-field infrared absorption are considered as model systems. The obtained IR spectra successfully reflect the spatial structure of the applied electric field and corresponding vibrational modes, demonstrating applicability of the present method to analyze modern nanovibrational spectroscopy using near-fields. The present method can use arbitral electric fields and thus can integrate two fields such as computational chemistry and electromagnetics. (C) 2016 AIP Publishing LLC.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu, Kristopher Keipert, Mark S. Gordon
    JOURNAL OF COMPUTATIONAL CHEMISTRY 37 5 487 - 493 2016年02月 [査読有り][通常論文]
     
    A new type of reaction pathway which involves a nontotally symmetric trifurcation was found and investigated for a typical S(N)2-type reaction, NC-+CH3X NCCH3+X- (X=F, Cl). A nontotally symmetric valley-ridge inflection (VRI) point was located along the C-3v reaction path. For X=F, the minimum energy path (MEP) starting from the transition state (TS) leads to a second-order saddle point with C-3v symmetry, which connects three product minima of C-s symmetry. For X=Cl, four product minima have been observed, of which three belong to C-s symmetry and one to C-3v symmetry. The branching path from the VRI point to the lower symmetry minima was determined by a linear interpolation technique. The branching mechanism is discussed based on the reaction path curvature and net atomic charges, and the possibility of a nonotally symmetric n-furcation is discussed. (c) 2015 Wiley Periodicals, Inc.
  • 小林正人, 黒田悠介, 秋葉欣哉, 武次徹也
    Journal of Computer Chemistry, Japan 14 199 - 200 2016年01月 [査読有り][通常論文]
  • Daniel Murdock, Rebecca A. Ingle, Igor V. Sazanovich, Ian P. Clark, Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda, Andrew J, Orr-Ewing, Michael, N.R. Ashfold
    Physical Chemistry Chemical Physics 18 4 2629 - 2638 2016年01月 [査読有り][通常論文]
     
    © the Owner Societies 2016. The photoisomerisation dynamics following excitation to the S 1 electronic state of two structurally related heterocyclic molecules, α-pyrone and coumarin, in acetonitrile solution have b een probed by time-resolved vibrational absorption spectroscopy. Following irradiation at 310 nm, α-pyrone relaxes rapidly from its initially excited state, with a quantum yield for parent molecule reformation of 68%. Probing the antisymmetric ketene stretch region between 2100 cm -1 and 2150 cm -1 confirms the presence of at least two isomeric ring-opened photoproducts, which are formed highly vibrationally excited and relax on a picosecond timescale. Following vibrational cooling, a secondary, thermally driven, isomerisation is observed with a 1.8(1) ns time constant. In contrast, coumarin reforms the parent molecule with essentially 100% efficiency following excitation at 330 nm. The conical intersections driving the non-radiative relaxation of α-pyrone have been investigated using an automated search algorithm. The two lowest energy conical intersections possess remarkably similar structures to the two energetically accessible conical intersections reported previously for coumarin, suggesting that the differing photochemistry is the result of dynamical effects occurring after passage through these intersections.
  • Yamazaki, Kaoru, Miyazaki, Yasunori, Harabuchi, Yu, Taketsugu, Tetsuya, Maeda, Satoshi, Inokuchi, Yoshiya, Kinoshita, Shin-nosuke, Sumida, Masataka, Onitsuka, Yuuki, Kohguchi, Hiroshi, Ehara, Masahiro, Ebata, Takayuki
    Journal of Physical Chemistry Letters 7 4001 - 4007 2016年 [査読有り][通常論文]
     
    © 2016 American Chemical Society. The nonradiative decay pathways of jet-cooled para-methoxy methylcinnamate (p-MMC) and para-methoxy ethylcinnamate (p-MEC) have been investigated by picosecond pump-probe and nanosecond UV-Deep UV pump-probe spectroscopy. The possible relaxation pathways were calculated by the (time-dependent) density functional theory. We found that p-MMC and p-MEC at low excess energy undergo multistep intersystem crossing (ISC) from the bright S 1 ( 1 ππ∗) state to the lowest triplet T 1 ( 3 ππ∗) state via two competing pathways through the T 2 state in the time scale of 100 ps: (a) stepwise ISC followed after the internal conversion (IC) from S 1 to the dark 1 nπ∗ state; (b) direct ISC from the S 1 to T 2 states. These picosecond multistep ISCs result in the torsion of C=C double bond by ∼95° in the T 1 state, whose measured adiabatic energy and lifetime are 16577 cm -1 and ∼20 ns, respectively, for p-MMC. These results suggest that the ISC processes play an indispensable role in the photoprotecting sunscreens in natural plants.
  • Ryo Iikubo, Taro Sekikawa, Yu Harabuchi, Tetsuya Taketsugu
    FARADAY DISCUSSIONS 194 147 - 160 2016年 [査読有り][通常論文]
     
    Femtosecond ring-opening dynamics of 1,3-cyclohexadiene (CHD) in gas phase upon two-photon excitation at 400 nm (=3.1 eV) was investigated by time-resolved photoelectron spectroscopy using 42 nm (=29.5 eV) high harmonic photons probing the dynamics of the lower-lying occupied molecular orbitals (MOs), which are the fingerprints of the molecular structure. After 500 fs, the photoelectron intensity of the MO constituting the C=C sigma bond (sigma(C=C)) of CHD was enhanced, while that of the MO forming the C-C sigma bond (sigma(CC)) of CHD was decreased. The changes in the photoelectron spectra suggest that the ring of CHD opens to form a 1,3,5-hexatriene (HT) after 500 fs. The dynamics of the sigma(C=C) and sigma(CC) bands between 200 and 500 fs reflects the ring deformation to a conical intersection between the 2(1)A and 1(1)A potential energy surfaces prior to the ring-opening reaction.
  • Yosuke Sumiya, Yutaka Nagahata, Tamiki Komatsuzaki, Tetsuya Taketsugu, Satoshi Maeda
    JOURNAL OF PHYSICAL CHEMISTRY A 119 48 11641 - 11649 2015年12月 [査読有り][通常論文]
     
    The significance of kinetic analysis as a tool for understanding the reactivity and selectivity of organic reactions has recently been recognized. However, conventional simulation approaches that solve rate equations numerically are not amenable to multistep reaction profiles consisting of fast and slow elementary steps. Herein, we present an efficient and robust approach for evaluating the overall rate constants of multistep reactions via the recursive contraction of the rate equations to give the overall rate constants for the products and byproducts. This new method was applied to the Claisen rearrangement of allyl vinyl ether, as well as a substituted allyl vinyl ether. Notably, the profiles of these reactions contained 23 and 84 local minima, and 66 and 278 transition states, respectively. The overall rate constant for the Claisen rearrangement of allyl vinyl ether was consistent with the experimental value. The selectivity of the Claisen rearrangement reaction has also been assessed using a substituted allyl vinyl ether. The results of this study showed that the conformational entropy in these flexible chain molecules had a substantial impact on the overall rate constants. This new method could therefore be used to estimate the overall rate constants of various other organic reactions involving flexible molecules.
  • Masato Kobayashi, Yusuke Kuroda, Kin-ya Akiba, Tetsuya Taketsugu
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 11 1584 - 1590 2015年11月 [査読有り][通常論文]
     
    The ligand coupling reaction (LCR) of hypervalent pentacoordinate antimony compounds (Ar(n)Tol(5-n)Sb; Ar = p-tri-fluoromethylphenyl, Tol = p-methylphenyl; n = 0-5) was analyzed via the long-range-corrected density functional theory. Although previous experimental or computational investigations have suggested apical apical or equatorial equatorial coupling of Ar(n)Tol(5-n)Sb compounds, the present results lead to apical equatorial coupling. The biased experimental ratios of the coupling products, which were grounds for apical apical coupling, can be explained by the stability of the transition-state (TS) structure for the apical equatorial coupling, where n-pi* interaction plays an important role to the stabilization. We further investigated the potential energy surface of H5Sb, for which the intrinsic reaction coordinate (IRC) from the TS structure for LCR indicates the equatorial equatorial coupling. It is found that the valley-ridge transition occurs along the IRC near the TS structure and the transverse vibrational mode with imaginary frequency, orthogonal to the IRC, directs to the reactant structure corresponding to the apical equatorial coupling.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    The Journal of Chemical Physics 143 17 177102  {AIP} Publishing 2015年11月 [査読有り][通常論文]
  • Kei Yanagisawa, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Tomoko Akama, Masato Kobayashi, Tetsuya Taketsugu, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2015 28 4769 - 4774 2015年10月 [査読有り][通常論文]
     
    Enhanced luminescence properties of mononuclear lanthanide complexes with asymmetric seven-coordination structures are reported for the first time. The lanthanide complexes are composed of a lanthanide ion (Eu-III or Tb-III), three tetramethyl heptanedionato ligands, and one triphenylphosphine oxide ligand. The coordination geometries of the lanthanide complexes have been evaluated by using single-crystal X-ray analyses and shape-measurement calculations. The complexes are categorized to be seven-coordinate monocapped octahedral structures (point group C-3v). The seven-coordinate lanthanide complexes show high intrinsic emission quantum yields, extra-large radiative rate constants, and unexpected small nonradiative rate constants. The brilliant luminescence properties have been elucidated in terms of the asymmetric coordination geometry and small vibrational quanta related to thermal relaxation.
  • Konstantin A. Simonov, Nikolay A. Vinogradov, Alexander S. Vinogradov, Alexander V. Generalov, Elena M. Zagrebina, Gleb I. Svirskiy, Attilio A. Cafolla, Thomas Carpy, John P. Cunniffe, Tetsuya Taketsugu, Andrey Lyalin, Nils Martensson, Alexei B. Preobrajenski
    ACS NANO 9 9 8997 - 9011 2015年09月 [査読有り][通常論文]
     
    Bottom-up strategies can be effectively implemented for the fabrication of atomically precise graphene nanoribbons. Recently, using 10,10'-dibromo-9,9'-bianthracene (DBBA) as a molecular precursor to grow armchair nanoribbons on Au(111) and Cu(111), we have shown that substrate activity considerably affects the dynamics of ribbon formation, nonetheless without significant modifications in the growth mechanism. In this paper we compare the on-surface reaction pathways for DBBA molecules on Cu(111) and Cu(110). Evolution of both systems has been studied via a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and theoretical calculations. Experimental and theoretical results reveal a significant increase in reactivity for the open and anisotropic Cu(110) surface in comparison with the close-packed Cu(111). This increased reactivity results in a predominance of the molecular substrate interaction over the intermolecular one, which has a critical impact on the transformations of DBBA on Cu(110). Unlike DBBA on Cu(111), the Ullmann coupling cannot be realized for DBBA/Cu(110) and the growth of nanoribbons via this mechanism is blocked. Instead, annealing of DBBA on Cu(110) at 250 degrees C results in the formation of a new structure: quasi-zero-dimensional flat nanographenes. Each nanographene unit has dehydrogenated zigzag edges bonded to the underlying Cu rows and oriented with the hydrogen-terminated armchair edge parallel to the [1-10] direction. Strong bonding of nanographene to the substrate manifests itself in a high adsorption energy of -12.7 eV and significant charge transfer of 3.46e from the copper surface. Nanographene units coordinated with bromine adatoms are able to arrange in highly regular arrays potentially suitable for nanotemplating.
  • Masato Kobayashi, Tetsuya Taketsugu
    Theoretical Chemistry Accounts 134 9 107  2015年08月 [査読有り][招待有り]
     
    © 2015, Springer-Verlag Berlin Heidelberg. In 2005, Surján showed two explicit formulas for evaluating the second-order Møller–Plesset perturbation (MP2) energy as a functional of the Hartree–Fock density matrix $$\varvec{D}$$D (Chem Phys Lett 406:318, 2005), which are referred to as the $$\Delta E_\text {MP2}[\varvec{D}]$$ΔEMP2[D] functionals. In this paper, we present the finite-temperature (FT) MP2 energy functionals of the FT Hartree–Fock density matrix. There are also two formulas for the FT-MP2, namely the conventional and renormalized ones; the latter of which has recently been formulated by Hirata and He (J Chem Phys 138:204112, 2013). We proved that there exists one-to-one correspondence between the formulas of two FT-MP2 and the $$\Delta E_\text {MP2}[\varvec{D}]$$ΔEMP2[D] functionals. This fact can explain the different behavior of two $$\Delta E_\text {MP2}[\varvec{D}]$$ΔEMP2[D] functionals when an approximate Hartree–Fock density matrix is applied, which was previously investigated by Kobayashi and Nakai (Chem Phys Lett 420:250, 2006). We also applied the FT-MP2 formalisms to the linear-scaling divide-and-conquer method for improving the accuracy with tiny addition of the computational efforts.
  • Ahmed M. El-Nahas, John M. Simmie, Ahmed H. Mangood, Kimihiko Hirao, Jong-Won Song, Mark A. Watson, Tetsuya Taketsugu, Nobuaki Koga
    MOLECULAR PHYSICS 113 13-14 1630 - 1635 2015年07月 [査読有り][招待有り]
     
    The enthalpies of formation for some selected oxygenates have been calculated by the atomisation energy approach using B3LYP, BHandHLYP, MPW3LYP, MPW1K, MPWB1K, BB1K, MPW1B95, BMK, and long-range corrected (LC-omega PBE, LC-BOP, LCgau-BOP, LC-BOP12, LCgau-B97) density functionals, as well as the composite CBS-QB3 method. Compared with experiment, BMK, LC-omega PBE, LCgau-BOP, LC-BOP12, LCgau-B97, MPW195, MPW3LYP functionals and CBS-QB3 give root mean square errors (RMSE) in enthalpies of formation no greater than 4 kcal/mol, whilst MPW1K and BHandHLYP show much worse performance (RMSE of 20-40 kcal/mol). The B3LYP, MPWB1K, and BB1K results fall between the two extremes. Energy barriers for the dominant paths in the unimolecular decomposition of simple esters (HCO2CH3, C2H5CO2C2H5), C1-C3 acids, and 1-butanol are reproduced well by CBS-QB3, BMK, BB1K, LCgau-B97, and PW1B95 (RMSE = 1-2 kcal/mol), while other LC methods (LC-omega PBE, LC-BOP, LCgau-BOP, and LC-BOP12) show a deviation of up to 4 kcal/mol. For the ionisation potentials, calculated from Koopman's theorem, all of the investigated LC-methods give good results compared with other density functional theory functionals with a maximum deviation of 0.4 eV, except for LCgau-B97, which has an RMSE of 0.7 eV.
  • Ryo Iikubo, Takehisa Fujiwara, Taro Sekikawa, Yu Harabuchi, Sota Satoh, Tetsuya Taketsugu, Yosuke Kayanuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 6 13 2463 - 2468 2015年07月 [査読有り][通常論文]
     
    Using 42 nm high harmonic pulses, the dissociation dynamics of 1,2-butadiene was investigated by time-resolved photoelectron spectroscopy (TRPES), enabling us to observe dynamical changes of multiple molecular orbitals (MOs) with higher temporal resolution than conventional light sources. Because each lower-lying occupied MO has particular spatial electron distribution, the structural dynamics of photochemical reaction can be revealed. On the femtosecond time scale, a short-lived excited state with a lifetime of 37 +/- 15 Is and the coherent oscillation of the photoelectron yield stimulated by Hertzberg-Teller coupling were observed. Ab initio molecular dynamics simulations in the electronically excited state find three relaxation pathways from the vertically excited structure in S-1 to the ground state, and one of them is the dominant relaxation pathway, observed as the short-lived excited state. On the picosecond time scale, the photoelectron yields related to the C-C bond decreased upon photoexcitation, indicating C-C bond cleavage.
  • Yu Harabuchi, Yuriko Ono, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 143 1 014301  2015年07月 [査読有り][通常論文]
     
    A global reaction route map is generated for Au-5 by the anharmonic downward distortion following method in which 5 minima and 14 transition states (TSs) are located. Through vibrational analyses in the 3N - 7 (N = 5) dimensional space orthogonal to the intrinsic reaction coordinate (IRC), along all the IRCs, four IRCs are found to have valley-ridge transition (VRT) points on the way where a potential curvature changes its sign from positive to negative in a direction orthogonal to the IRC. The detailed mechanisms of bifurcations related to the VRTs are discussed by surveying a landscape of the global reaction route map, and the connectivity of VRT points and minima is clarified. Branching of the products through bifurcations is confirmed by ab initio molecular dynamics simulations starting from the TSs. A new feature of the reaction pathways, unification, is found and discussed. (C) 2015 AIP Publishing LLC.
  • Min Gao, Andrey Lyalin, Makito Takagi, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 119 20 11120 - 11130 2015年05月 [査読有り][招待有り]
     
    This work present results of a systematic investigation of adsorption and dissociation of H-2 on the neutral, positively, and negatively charged gold clusters Au-n(q) (n = 2-11; q = 0; +/- 1) using the global reaction route mapping (GRRM) technique combined with the anharmonic downward distortion following (ADDF) and the artificial force-induced reaction (AFIR) methods. An exhaustive search for H-2 dissociation pathways is performed not only on the most stable cluster structures but also on the large number of low-energy isomers, allowing structural transformations between them. The present strategy can automatically identify the structure-dependent lowest transition states (TS) for H-2 dissociation with a systematic procedure in the regime of the structural fluxionality of gold clusters at finite temperature. Temperature effects, cluster isomerization, and influence of the charge state of gold clusters on H-2 adsorption and dissociation are studied. It is demonstrated that the most stable structures of the gold clusters are not always highly reactive, and an ensemble of isomeric structures must be taken into account for adequate description of the reaction rates at finite temperatures. The proposed approach can serve as a promising tool for a systematic analysis and prediction of reactivity of small metal clusters.
  • Ryohei Uematsu, Eiji Yamamoto, Satoshi Maeda, Hajime Ito, Tetsuya Taketsugu
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 12 4090 - 4099 2015年04月 [査読有り][通常論文]
     
    Theoretical and experimental studies have been conducted to elucidate the mechanism of the formal nucleophilic boryl substitution of aryl and alkyl bromides with silylborane in the presence of potassium methoxide. Density functional theory was used in conjunction with the artificial force induced reaction method in the current study to determine the mechanism of this reaction. The results of this analysis led to the identification of a unique carbanion-mediated mechanism involving the halogenophilic attack of a silyl nucleophile on the bromine atom of the substrate. These calculations have, therefore, provided a mechanistic rationale for this counterintuitive borylation reaction. Furthermore, the good functional group compatibility and high reactivity exhibited by this reaction toward sterically hindered substrates can be understood in terms of the low activation energy required for the reaction of the silyl nucleophile with the bromine atom of the substrate and the subsequent rapid and selective consumption of the carbanion species by the in situ generated boron electrophile. The results of an experimental study involving the capture of the anion intermediate provided further evidence in support of the generation of a carbanion species during the course of this reaction. The anomalous formal nucleophilic borylation mechanism reported in this study could be used to provide new insights into silicon and boron chemistry.
  • Satoshi Maeda, Yu Harabuchi, Yuriko Ono, Tetsuya Taketsugu, Keiji Morokuma
    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 115 5 258 - 269 2015年03月 [査読有り][招待有り]
     
    The intrinsic reaction coordinate (IRC) approach has been used extensively in quantum chemical analysis and prediction of the mechanism of chemical reactions. The IRC gives a unique connection from a given transition structure to local minima of the reactant and product sides. This allows for easy understanding of complicated multistep mechanisms as a set of simple elementary reaction steps. In this article, three topics concerning the IRC approach are discussed. In the first topic, the first ab initio study of the IRC and a recent development of an IRC calculation algorithm for enzyme reactions are introduced. In the second topic, cases are presented in which dynamical trajectories bifurcate and corresponding IRC connections can be inaccurate. In the third topic, a recent development of an automated reaction path search method and its application to systematic construction of IRC networks are described. Finally, combining these three topics, future perspectives are discussed. (c) 2014 Wiley Periodicals, Inc.
  • Satoshi Maeda, Tetsuya Taketsugu, Koichi Ohno, Keiji Morokuma
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 10 3433 - 3445 2015年03月 [査読有り][招待有り]
     
    The photodissociation of small molecules occurs upon irradiation by ultraviolet visible light, and it is a very important Chemical process in Earth's atmosphere, in the atmospheres of other planets, and in interstellar media. Photodissociation is an important method used to thoroughly investigate the fundamental issues of chemical,reactivity. Photodissociation involves Molecules and reaction fragments moving over ground and excited-state potential surfaces (PESs). Molecules can move on a single PES (adiabatic pathway) or can cross over from one PES to another (nondiabatic pathways). For a full theoretical understanding Of a photodissociation mechanism, all of the important nonadiabatic and adiabatic pathway must be determined. This is not an easy task. We have developed an efficient computational method, called the global reaction route mapping (GRRM) strategy, that allows a, theoretical exploration of ground- and excited-state PESs and their crossing seams in an automatic manner. In this Perspective, we summarize our approaches and present examples of their application together with newly determined chemical insights. These include the complex photodissociation mechanism of the formaldehyde molecule,, the exclusive excited-state roaming dynamics of the nitrate radical, and all product channels and conformational memory in the photodissociation of the formic acid molecule. Finally, perspectives for the theoretical design of photofunctional molecules ate discussed.
  • Cheng Zhu, Keisuke Niimi, Tetsuya Taketsugu, Masashi Tsuge, Akira Nakayama, Leonid Khriachtchev
    JOURNAL OF CHEMICAL PHYSICS 142 5 054305  2015年02月 [査読有り][通常論文]
     
    Experimental and theoretical studies of HXeI and HXeH molecules in Ar, Kr, and Xe matrices are presented. HXeI exhibits the H-Xe stretching bands at 1238.0 and 1239.0 cm(-1) in Ar and Kr matrices, respectively, that are blue-shifted from the HXeI band observed in a Xe matrix (1193 cm(-1)) by 45 and 46 cm(-1). These shifts are larger than those observed previously for HXeCl (27 and 16 cm(-1)) and HXeBr (37 and 23 cm(-1)); thus, the matrix effect is stronger for less stable molecules. The results for HXeI are qualitatively different from all previous results on noble-gas hydrides with respect to the frequency order between Ar and Kr matrices. For previously studied HXeCl, HXeBr, and HXeCCH, the H-Xe stretching frequency is reliably (by > 10 cm(-1)) higher in an Ar matrix than in a Kr matrix. In contrast, the H-Xe stretching frequency of HXeI in an Ar matrix is slightly lower than that in a Kr matrix. HXeH absorbs in Ar and Kr matrices at 1203.2 and 1192.1 cm(-1) (the stronger band for a Kr matrix), respectively. These bands are blue-shifted from the stronger band of HXeH in a Xe matrix (1166 cm(-1)) by 37 and 26 cm(-1), and this frequency order is the same as observed for HXeCl, HXeBr, and HXeCCH but different from HXeI. The present hybrid quantum-classical simulations successfully describe the main experimental findings. For HXeI in the < 110 > (double substitution) site, the order of the H-Xe stretching frequencies (nu(Xe) < nu(Ar) < nu(Kr)) is in accord with the experimental observations, and also the frequency shifts in Ar and Kr matrices from a Xe matrix are well predicted (30 and 34 cm(-1)). Both in the theory and experiment, the order of the H-Xe stretching frequencies differs from the case of HXeCl, which suggests the adequate theoretical description of the matrix effect. For HXeH in the < 100 > (single substitution) site, the order of the frequencies is nu(Xe) < nu(Kr) < nu(Ar), which also agrees with the experiments. The calculated frequency shifts for HXeH in Ar and Kr matrices with respect to a Xe matrix (36 and 23 cm(-1)) are in a good agreement with the experiments. The present calculations predict an increase of the H-Xe stretching frequencies in the noble-gas matrices with respect to vacuum. (C) 2015 AIP Publishing LLC.
  • Kosuke Namba, Ayumi Osawa, Akira Nakayama, Akane Mera, Fumi Tano, Yoshiro Chuman, Eri Sakuda, Tetsuya Taketsugu, Kazuyasu Sakaguchi, Noboru Kitamura, Keiji Tanino
    CHEMICAL SCIENCE 6 2 1083 - 1093 2015年 [査読有り][通常論文]
     
    To expand the originally developed fluorescent 1,3a, 6a-triazapentalenes as fluorescent labelling reagents, the fluorescence wavelength of the 1,3a, 6a-triazapentalenes was extended to the red color region. Based on the noteworthy correlation of the fluorescence wavelength with the inductive effect of the 2-substituent, electron-deficient 2-(2-cyano-4-methoxycarbonylphenyl)-1,3a, 6a-triazapentalene and 2-(2,6-dicyano-4-methoxycarbonylphenyl)-1,3a, 6a-triazapentalene were synthesized. The former exhibited yellow fluorescence and the latter exhibited red fluorescence, and both compounds exhibited large Stokes shifts, and the 1,3a, 6a-triazapentalene system enabled the same fluorescent chromophore to cover the entire region of visible wavelengths. The potential applications of the 1,3a, 6a-triazapentalenes as fluorescent probes in the fields of the life sciences were investigated, and the 1,3a, 6a-triazapentalene system was clearly proven to be useful as a fluorescent reagent for live cell imaging. Quantum chemical calculations were performed to investigate the optical properties of the 1,3a, 6a-triazapentalenes. These calculations revealed that the excitation involves a significant charge-transfer from the 1,3a, 6a-triazapentalene skeleton to the 2-substituent. The calculated absorption and fluorescence wavelengths showed a good correlation with the experimental ones, and thus the system could enable the theoretical design of substituents with the desired optical properties.
  • Yu Harabuchi, Tetsuya Taketsugu, Satoshi Maeda
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 35 22561 - 22565 2015年 [査読有り][通常論文]
     
    Minimum energy conical intersection (MECI) geometries were searched for polycyclic aromatic hydrocarbons (PAHs) consisting of up to 26 atoms. The energy barriers to the obtained MECIs showed a correlation with their fluorescence quantum yields. This provides a theoretical rationale for the size dependence of the fluorescence quantum yields seen in these PAHs.
  • Keisuke Niimi, Tetsuya Taketsugu, Akira Nakayama
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 17 12 7872 - 7880 2015年 [査読有り][通常論文]
     
    The matrix shifts of the H-Xe stretching frequency of noble-gas hydrides, HXeCCH, HXeBr, and HXeI in various noble-gas matrices (in Ne, Ar, Kr, and Xe matrices) are investigated via the hybrid quantum-classical simulations. The order of the H-Xe stretching frequencies is found to be v(gas) < v(Ne) < v(Xe) < v(Kr) < v(Ar) for HXeCCH and HXeBr, while it is v(gas) < v(Ne) < v(Xe) < v(Ar) < v(Kr) for HXeI. This order is anomalous with respect to the matrix dielectric constants, and the calculated results reproduce the experimentally observed shifts quite successfully. We also find that the matrix shifts from the gas-phase values are Delta v(HXeCCH) approximate to Delta v(HXeCl) < Delta v(HXeBr) < Delta v(HXeI) in the same noble-gas matrix environments, which implies that the weakly bound molecules exhibit large matrix shifts. The local trapping site is analyzed in detail, and it is shown that a realistic modeling of the surrounding matrix environments is essential to describe the unusual matrix shifts accurately.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma, Koichi Ohno
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 87 12 1315 - 1334 2014年12月 [査読有り][招待有り]
     
    This article gives a comprehensive review of the anharmonic downward distortion following (ADDF) method. The ADDF method has been developed as an automated reaction path search method. This method follows the anharmonic downward distortion (ADD) toward transition states and dissociation channels starting from a local minimum on the potential energy surface (PES). Systematic applications of the ADDF method to all local minima provide a global network of reaction pathways on the PES of given chemical formulas. Various extensions have been proposed and applied to many interesting chemical problems such as elucidation of photodissociation mechanisms, structure prediction of H-bonded clusters, mechanistic studies of organometallic catalysis, design of generation-conversion routes of amino acid molecules, and so on. It has also been employed in efficient construction of anharmonic PESs for highly accurate vibrational analysis. These developments and applications are illustrated with some representative results.
  • Satoshi Maeda, Yu Harahuchi, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY A 118 51 12050 - 12058 2014年12月 [査読有り][招待有り]
     
    Locating accessible conical intersections (CIs), especially minimum energy CI (MECI) structures, near the Franck-Condon (FC) region is one of the most important tasks in theoretical analyses of photoreactions. Many MECIs may exist around a FC point in molecules with many vibrational degrees of freedom. Usually, MECIs are optimized one by one starting from arbitrary chosen initial structures. In order to eliminate the arbitrariness, we have developed automated MECI search methods. In this paper, a new approach is described. It combines the seam model function approach with the recently proposed single-component artificial force induced reaction method. Starting from a FC point, the present method finds MECIs systematically. It requires neither a Hessian nor a derivative coupling vector. In an example of the automated search, the spin-flip TDDFT was employed as an efficient electronic structure calculation method, which, together with an automated algorithm to recognize proper electronic states, allowed for evaluation of energy and gradient in a black-box fashion. The present approach was tested with trans- and cis-1,3-butadiene, thymine, and coumarin molecules. The usefulness of the present approach was demonstrated by comparing obtained MECIs with those in the literature. It is hoped that the present technique will be useful in exploration of unknown photoreaction pathways.
  • Yu Harabuchi, Kristopher Keipert, Federico Zahariev, Tetsuya Taketsugu, Mark S. Gordon
    The Journal of Physical Chemistry A 118 51 11987 - 11998 2014年12月 [査読有り][招待有り]
     
    © 2014 American Chemical Society. On-the-fly dynamics simulations were carried out using spinflip time dependent density functional theory (SF-TDDFT) to examine the photoisomerization and photocyclization mechanisms of cis-stilbene following excitation to the ππ∗ state. A state tracking method was devised to follow the target state among nearly degenerate electronic states during the dynamics simulations. The steepest descent path from the Franck-Condon structure of cis-stilbene in the ππ∗ state is shown to reach the S 1 -minimum of 4,4-dihydrophenanthrene (DHP) via a cis-stilbene-like structure (referred to as (S 1 ) cis-min ) on a very flat region of the S 1 -potential energy surface. From the dynamics simulations, the branching ratio of the photoisomerization is calculated as trans:DHP = 35:13, in very good agreement with the experimental data, trans:DHP = 35:10. The discrepancy between the steepest descent pathway and the significant trans-stilbene presence in the branching ratio observed experimentally and herein computationally is clarified from an analysis of geometrical features along the reaction pathway, as well as the low barrier of 0.1 eV for the pathway from (S 1 ) cis-min to the twisted pyramidal structure on the S 1 -potential energy surface. It is concluded that ππ∗-excited cis-stilbene propagates primarily toward the twisted structural region due to dynamic effects, with partial branching to the DHP structural region via the flat-surface region around (S 1 ) cis-min . (Figure Presented).
  • Akira Nakayama, Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 118 40 9429 - 9437 2014年10月 [査読有り][通常論文]
     
    The nonradiative deactivation pathways of cytosine derivatives (cytosine, 5-fluorocytosine, 5-methylcytosine, and 1-methyc-ytosine) and their tautomers are investigated by quantum chemical calculations, and the substituent effects on the deactivation process are examined. The MS-CASPT2 method is employed in the excited-state geometry optimization and also in the search for conical intersection points, and the potential energy profiles connecting the Franck-Condon point, excited-state minimum energy structures, and the conical intersection points are investigated. Our calculated vertical and adiabatic excitation energies are in quite good agreement with the experimental results, and the relative barrier heights leading to the conical intersections are correlated with the experimentally observed excite-state lifetimes, where the calculated barrier heights are in the order of cytosine < 5-methylcytosine < 5-fluorocytosine.
  • Andrey Lyalin, Akira Nakayama, Kohei Uosaki, Tetsuya Taketsugu
    TOPICS IN CATALYSIS 57 10-13 1032 - 1041 2014年06月 [査読有り][招待有り]
     
    Adsorption and catalytic activation of the molecular oxygen on the hexagonal boron nitride (h-BN) monolayer supported on Ni(111) and Cu(111) surfaces have been studied theoretically using density functional theory. It is demonstrated that an inert h-BN monolayer can be functionalized and become catalytically active on the transition metal support as a result of mixing of the metal d and h-BN pi bands.
  • Kohei Uosaki, Ganesan Elumalai, Hidenori Noguchi, Takuya Masuda, Andrey Lyalin, Akira Nakayama, Tetsuya Taketsugu
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 18 6542 - 6545 2014年05月 [査読有り][通常論文]
     
    Boron nitride (BN), which is an insulator with a wide band gap, supported on Au is theoretically suggested and experimentally proved to act as an electrocatalyst for oxygen reduction reaction (ORR). Density-functional theory calculations show that the band gap of a free h-BN monolayer is 4.6 eV but a slight protrusion of the unoccupied BN states toward the Fermi level is observed if BN is supported on Au(III) due to the BN-Au interaction. A theoretically predicted metastable configuration of O-2 on h-BN/Au(III), which can serve as precursors for ORR, and free energy diagrams for ORR on h-BN/Au(III) via two- and four-electron pathways show that ORR to H2O2 is possible at this electrode. It is experimentally proved that overpotential for ORR at the gold electrode is significantly reduced by depositing BN nanosheets. No such effect is observed at the glassy carbon electrode, demonstrating the importance of BN substrate interaction for h-BN to act as the ORR electrocatalyst. A possible role of the edge of the BN islands for ORR is also discussed.
  • 前田理, 畑中美穂, 植松遼平, 武次徹也, 諸熊奎治
    有機合成化学協会誌 72 5 567 - 579 2014年05月 [査読有り][招待有り]
     
    Theory has become one of important tools in synthetic organic chemistry. The transition state (TS) of chemical reactions can be visualized by geometry optimizations. This helps to design novel reactions. However, there has been a serious problem. That is, how to prepare initial structures for all relevant TSs. An optimization starting from a bad structure fails to converge. Moreover, geometry optimization cannot find unexpected TSs. The latter prohibits reliable analysis and prediction of mechanisms in highly complicated, multistep reactions. In order to solve this problem, we have developed automated reaction path search methods. In this paper, the artificial force induced reaction (AFIR) method and some examples of its applications are described. The AFIR method would expand applicability of theory dramatically.
  • Ayumu Makida, Hironori Igarashi, Takehisa Fujiwara, Taro Sekikawa, Yu Harabuchi, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 5 10 1760 - 1765 2014年05月 [査読有り][通常論文]
     
    In trans-1,3-butadiene, the ultrafast relaxation from the doubly excited state 2(1)A(g) and the corresponding recovery of the ground state 1(1)A(g) were observed simultaneously for the first time by time-resolved photoelectron spectroscopy (TRPES) using 29.5 eV high harmonic pulses. The fast recovery of 1(1)A(g) shows that the following dissociation upon photoexcitation takes place after returning to the ground state. At 427 fs after photoexcitation, only the ionization energy from the C=C sigma bond was found to remain shifted. Accompanying theoretical calculations with an assumption of Koopmans' theorem show that the ionization energy of the C=C sigma bond is modulated by vibrational excitation of the antisymmetric C=C stretching mode. TRPES by high harmonics can probe the changes in the molecular structure sensitively.
  • Guixiang Zeng, Satoshi Maeda, Tetsuya Taketsugu, Shigeyoshi Sakaki
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 53 18 4633 - 4637 2014年04月 [査読有り][通常論文]
     
    Main-group-element catalysts are a desirable alternative to transition-metal catalysts because of natural abundance and cost. However, the examples are very limited. Catalytic cycles involving a redox process and E-ligand cooperation (E=main-group element), which are often found in catalytic cycles of transition-metal catalysts, have not been reported. Herein theoretical investigations of a catalytic hydrogenation of azobenzene with ammonia-borane using a trivalent phosphorus compound, which was experimentally proposed to occur through P-III/P-V redox processes via an unusual pentavalent dihydridophosphorane, were performed. DFT and ONIOM(CCSD(T):MP2) calculations disclosed that this catalytic reaction occurs through a P-O cooperation mechanism, which resembles the metal-ligand cooperation mechanism of transition-metal catalysts.
  • Min Gao, Andrey Lyalin, Satoshi Maeda, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 10 4 1623 - 1630 2014年04月 [査読有り][通常論文]
     
    A new theoretical approach to find metal-cluster-catalyzed single bond activation pathways is introduced. The proposed approach combines two automated reaction path search techniques: the anharmonic downward distortion following (ADDF) and the artificial force induced reaction (AFIR) methods, developed in our previous works [Maeda, S.; Ohno, K.; Morokuma, K. Phys. Chem. Chem. Phys. 2013, IS, 3683-3701]. A simple model reaction of the H-H bond activation catalyzed by Au-n (n = 7,8) clusters is considered as an example. We have automatically found 33 and 20 transition-state (TS) structures for H-2 dissociation on Au-7 and Au-8 clusters, respectively, and successfully identified the best dissociation pathways with the lowest barrier. Systematic analysis of the structure-dependent reactivity of small gold clusters is performed. It is demonstrated that the most stable structures of the gold clusters are not always highly reactive and several isomeric structures must be taken into account for adequate description of the reaction rates at finite temperatures. The proposed approach can serve as a promising tool for investigation of the chemical reactions catalyzed by small metal clusters.
  • Shohei Yamazaki, Shu-hei Urashima, Hiroyuki Saigusa, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 118 6 1132 - 1141 2014年02月 [査読有り][通常論文]
     
    The photophysical behavior of three lowest-energy tautomers of uric acid and seven most stable isomers of uric acid monohydrate is comprehensively studied by ab initio calculations. Ground-state energies are calculated with the CCSD(T) method, while excitation and ionization energies as well as excited-state potential energy profiles of photoinduced processes are calculated with the CC2 method. For the (1)pi pi* state, it is found that the excitation energy of the monohydrate cluster is significantly lower than that of isolated uric acid when the water molecule is hydrogen-bonded at a specific carbonyl group. The calculated excited-state potential energy profiles suggest that some monohydrate isomers can undergo a migration of the water molecule from one site to another site in the (1)pi pi* state with a small energy barrier. It is also found for both uric acid and its monohydrate that nonradiative decay via the NH bond dissociation in the (1)pi sigma* state is likely to occur at higher excitation energies. On the basis of the computational results, possible mechanisms for the absence of specific isomers of uric acid monohydrate from the resonant two-photon ionization spectrum are discussed.
  • Yu Harabuchi, Satoshi Maeda, Tetsuya Taketsugu, Koichi Ohno
    CHEMISTRY LETTERS 43 2 193 - 195 2014年02月 [査読有り][通常論文]
     
    A direct reaction pathway for water gas shift reaction (WGSR) in gas phase, H2O + CO -> H-2 + CO2, was discovered by using anharmonic downward distortion following method. The direct WGSR is accompanied by a roaming-like mechanism. To examine the initial conditions of the direct WGSR, we carried out ab initio molecular dynamics simulations and showed that cooperative excitations of OH-stretching vibrational modes and the orientational control of reactants are required for the direct WGSR.
  • Ryohei Uematsu, Satoshi Maeda, Tetsuya Taketsugu
    CHEMISTRY-AN ASIAN JOURNAL 9 1 305 - 312 2014年01月 [査読有り][通常論文]
     
    A systematic search for reaction pathways for the vinylogous Mannich-type reaction was performed by the artificial force induced reaction method. This reaction affords -amino--butenolide in one pot by mixing 2-trimethylsiloxyfuran, imine, and water under solvent-free conditions. Surprisingly, the search identified as many as five working pathways. Among them, two concertedly produce anti and syn isomers of the product. Another two give an intermediate, which is a regioisomer of the main product. This intermediate can undergo a retro-Mannich reaction to give a pair of intermediates: an imine and 2-furanol. The remaining pathway directly generates this intermediate pair. The imine and 2-furanol easily react with each other to afford the product. Thus, all of these stepwise pathways finally converge to give the main product. The rate-determining step of all five (two concerted and three stepwise) pathways have a common mechanism: concerted SiO bond formation through the nucleophilic attack of a water molecule on the silicon atom followed by proton transfer from the water molecule to the imine. Therefore, these five pathways have comparable barriers and compete with each other.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF COMPUTATIONAL CHEMISTRY 35 2 166 - 173 2014年01月 [査読有り][通常論文]
     
    Finding all required transition state (TS) structures is an important but hard task in theoretical study of complex reaction mechanisms. In the present article, an efficient automated TS search method, artificial force induced reaction (AFIR), was extended to intramolecular reactions. The AFIR method has been developed for intermolecular associative pathways between two or more reactants. Although it has also been applied to intramolecular reactions by dividing molecules manually into fragments, the fragmentation scheme was not automated. In this work, we propose an automated fragmentation scheme. Using this fragmentation scheme and the AFIR method, a fully automated search algorithm for intramolecular pathways is introduced. This version for intramolecular reactions is called single-component AFIR (SC-AFIR), to distinguish it from multicomponent AFIR for intermolecular reactions. SC-AFIR was tested with two reactions, the Claisen rearrangement and the first step of cobalt-catalyzed hydroformylation, and successfully located all important pathways reported in the literature. (c) 2013 Wiley Periodicals, Inc.
  • Keisuke Niimi, Akira Nakayama, Yuriko Ono, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 118 2 380 - 387 2014年01月 [査読有り][通常論文]
     
    The hybrid quantum-classical simulations are performed to investigate the unusual vibrational spectral shifts of a noble-gas hydride HXeCl in matrix environments (in Ne, Ar, Kr, and Xe matrixes). The high-level ab initio calculations at the CCSD(T) level are employed to construct interaction potential energy surfaces between HXeCl and noble-gas atoms (Ne, Ar, Kr, and Xe). The configurations of noble-gas atoms are sampled by the Monte Carlo simulations and the vibrational levels of HXeCl in the presence of the surrounding noble-gas atoms are solved by the DVR approach. It is found that the H-Xe stretching frequencies are blue-shifted from the isolated gas-phase value in all matrix environments and that the relative blue shifts are in good agreement with the experimental results (Ne < Xe < Kr), demonstrating that the explicit treatment of matrix environments around HXeCl is essential to reproduce the observed unusual vibrational shifts.
  • Akira Nakayama, Gaku Arai, Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 139 21 214304  2013年12月 [査読有り][通常論文]
     
    On-the-fly excited-state quantum mechanics/molecular mechanics molecular dynamics (QM/MM-MD) simulations of thymine in aqueous solution are performed to investigate the role of solvent water molecules on the nonradiative deactivation process. The complete active space second-order perturbation theory (CASPT2) method is employed for a thymine molecule as the QM part in order to provide a reliable description of the excited-state potential energies. It is found that, in addition to the previously reported deactivation pathway involving the twisting of the C-C double bond in the pyrimidine ring, another efficient deactivation pathway leading to conical intersections that accompanies the out-of-plane displacement of the carbonyl group is observed in aqueous solution. Decay through this pathway is not observed in the gas phase simulations, and our analysis indicates that the hydrogen bonds with solvent water molecules play a key role in stabilizing the potential energies of thymine in this additional decay pathway. (C) 2013 AIP Publishing LLC.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    Zeitschrift fur Physikalische Chemie 227 9-11 1421 - 1433 2013年11月 [査読有り][招待有り]
     
    The present study demonstrates a priori prediction of the mechanism of Paternò-Büchi (PB) reaction by automated search for reaction pathways using the artificial force induced reaction (AFIR) method, for the simplest set of reactants, H 2 CO + C 2 H 4 . The search found all previously suggested pathways automatically without using any guess about the reaction mechanism. Even the reaction product was not assumed. In addition, a comprehensive view of the reaction path network obtained in the present extensive search gave new insights into the mechanism. Barriers on excited states explained the preference of the initial bonding sites. A seam of crossing between the lowest triplet and first singlet excited state is suggested to make a significant contribution to an intersystem crossing and the reaction mechanism of the present system.© by Oldenbourg Wissenschaftsverlag, München.
  • Andrey Lyalin, Akira Nakayama, Kohei Uosaki, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 117 41 21359 - 21370 2013年10月 [査読有り][通常論文]
     
    The catalytic activity for the oxygen reduction reaction (ORR) of a hexagonal boron nitride (h-BN) monolayer supported on a Ni(111) surface has been studied theoretically using density-functional theory. It is shown that the Ni(111) support can critically change the chemical and physical properties of defect-free monolayer h-BN, considerably promoting the adsorption of O-2, OOH, OH, and O species, and therefore, it is demonstrated that inert defect-free monolayer h-BN can be functionalized by the metal support and become catalytically active for the ORR. Although simple potential-dependent modeling of the energetics of the ORR on h-BN/Ni(111) indicates the limitation of the ORR process due to the large overpotential, our calculations demonstrate the ability to fiinctionalize inert materials for the ORR and open new ways to design effective Pt-free catalysts for fuel-cell technology.
  • Yu Harabuchi, Satoshi Maeda, Tetsuya Taketsugu, Noriyuki Minezawa, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 9 9 4116 - 4123 2013年09月 [査読有り][通常論文]
     
    Automated search for minimum energy conical intersection geometries between the lowest two singlet states (S-0/S-1-MECIs) was performed by combining the anharmonic downward distortion following (ADDF) method, the seam model function (SMF) approach, and the spin-flip (SF) TDDFT method. SMF/ADDF has been employed previously in automated searches for MECIs on potential energy surfaces (PESs) with expensive multireference methods. In this work, we adopt the SF-TDDFT method that enables efficient optimization of S-0/S-1-MECIs in the framework of TDDFT. To evaluate the performance of the present approach, it was applied to ethylene and 1,3-butadiene. The present method automatically gave unknown S-0/S-1-MECIs as well as all previously reported ones. Therefore, the present hybrid method of SMF/ADDF and SF-TDDFT is shown to be a promising approach to locate S-0/S-1-MECIs of large systems automatically with modest computational costs.
  • Takeshi Matsumoto, Ho-Chol Chang, Masanori Wakizaka, Sho Ueno, Atsushi Kobayashi, Akira Nakayama, Tetsuya Taketsugu, Masako Kato
    Journal of the American Chemical Society 135 23 8646 - 8654 2013年06月12日 [査読有り][通常論文]
     
    The combination of o-phenylenediamine (opda), which possesses two proton- and electron-pooling capability, with Fe(II) leads to the photochemical hydrogen-evolution reaction (HER) in THF at room temperature without addition of photosensitizers. From the THF solution, the tris(o-phenylenediamine) iron(II) complex, [FeII(opda)3](ClO4)2 (1), was isolated as a photoactive species, while the deprotonated oxidized species was characterized by X-ray crystallographic analysis, electrospray ionization mass spectrometry, and UV-vis NIR spectra. Furthermore, the HER is photocatalyzed by hydroquinone, which serves as a H+/e- donor. The present work demonstrates that the use of a metal-bound aromatic amine as a H+/e- pooler opens an alternative strategy for designing nonprecious-metal-based molecular photochemical H2 production/storage materials. © 2013 American Chemical Society.
  • Harabuchi Y, Ishii M, Nakayama A, Noro T, Taketsugu T
    The Journal of Chemical Physics 138 6 064305  6 2013年02月14日 [査読有り][通常論文]
     
    A multireference second-order perturbation theory is applied to calculate equilibrium structures and vibrational frequencies of trans-azobenzene in the ground and nπ* excited states, as well as the reaction pathways for rotation and inversion mechanism in the nπ* excited state. It is found that the NN stretching frequency exhibits a slight increase at the minimum energy structure in the nπ* state, which is explained by the mixing of the NN stretching mode with the CN symmetric stretching mode. We also calculate the NN stretching frequency at several selected structures along the rotation and inversion pathways in the nπ* state, and show that the frequency decreases gradually along the rotation pathway while it increases by ca. 300 cm-1 along the inversion pathway. The frequencies and energy variations along the respective pathways indicate that the rotation pathway is more consistent with the experimental observation of the NN stretching frequency in nπ* excitation. © 2013 American Institute of Physics.
  • Min Gao, Andrey Lyalin, Tetsuya Taketsugu
    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 113 4 443 - 452 2013年02月 [査読有り][通常論文]
     
    Molecular and dissociative adsorption of O2 on Au atoms supported on the regular and defected hexagonal boron nitride (h-BN) surface has been studied theoretically using density functional theory. It is shown that even weak interaction of Au with the defect-free h-BN support has an unusually strong influence on the binding and catalytic activation of the molecular oxygen. The strong interaction of Au with vacancy point defects on the h-BN surface is accompanied by the large charge transfer to/from the adsorbate which can considerably affect the catalytic activity of the supported Au. It is demonstrated that activation of the molecular O2 and barriers for O2 dissociation on the supported Au atom can be affected by the interaction of Au with the pristine or defected h-BN support. Therefore, the h-BN surface cannot be considered as an absolutely inert support for Au. (C) 2012 Wiley Periodicals, Inc.
  • Min Gao, Andrey Lyalin, Tetsuya Taketsugu
    Journal of Chemical Physics 138 3 034701  2013年01月21日 [査読有り][通常論文]
     
    The mechanism of CO oxidation by O2 on Au atoms supported on the pristine and defected hexagonal boron nitride (h-BN) surface has been studied theoretically using density functional theory. It is found that O2 binds stronger than CO on an Au atom supported on the defect free h-BN surface and h-BN surface with nitrogen vacancy (VN@h-BN), but weaker than CO on a free Au atom or Au trapped by a boron vacancy (VB@h-BN). The excess of the positive or negative charge on Au can considerably change its catalytic properties and enhance activation of the adsorbed O2. Coadsorption of CO and O2 on Au, Au/VN@h-BN, and Au/V B@h-BN results in additional charge transfer to O2. Various pathways of the CO oxidation reaction by molecular oxygen are studied. We found two different pathways for CO oxidation: a two-step pathway where two CO2 molecules are formed independently, and a self-promotion pathway where oxidation of the first CO molecule is promoted by the second CO molecule. Interaction of Au with the defect-free and defected h-BN surface considerably affects the CO oxidation reaction pathways and barriers. Therefore, Au supported on the h-BN surface (pristine or defected) cannot be considered as pseudo-free atom and support effects have to be taken into account, even when the interaction of Au with the support is weak. © 2013 American Institute of Physics.
  • Andrey Lyalin, Akira Nakayama, Kohei Uosaki, Tetsuya Taketsugu
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 8 2809 - 2820 2013年 [査読有り][通常論文]
     
    The catalytic activity for the oxygen reduction reaction (ORR) of both the pristine and defect-possessing hexagonal boron nitride (h-BN) monolayer and H-terminated nanoribbon have been studied theoretically using density functional theory. It is demonstrated that an inert h-BN monolayer can be functionalized and become catalytically active by nitrogen doping. It is shown that the energetics of adsorption of O-2, O, OH, OOH, and H2O on N atom impurities in the h-BN monolayer (N-B@h-BN) is quite similar to that known for a Pt(111) surface. The specific mechanism of destructive and cooperative adsorption of ORR intermediates on the surface point defects is discussed. It is demonstrated that accounting for entropy and zero-point energy (ZPE) corrections results in destabilization of the ORR intermediates adsorbed on N-B@h-BN, while solvent effects lead to their stabilization. Therefore, entropy, ZPE and solvent effects partly cancel each other and have to be taken into account simultaneously. Analysis of the free energy changes along the ORR pathway allows us to suggest that a N-doped h-BN monolayer can demonstrate catalytic properties for the ORR under the condition that electron transport to the catalytically active center is provided.
  • Akira Nakayama, Yu Harabuchi, Shohei Yamazaki, Tetsuya Taketsugu
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 29 12322 - 12339 2013年 [査読有り][通常論文]
     
    A comprehensive picture of the ultrafast nonradiative decay mechanisms of three cytosine tautomers (amino-keto, imino-keto, and amino-enol forms) is revealed by high-level ab initio potential energy calculations using the multistate (MS) CASPT2 method and also by on-the-fly excited-state molecular dynamics simulations employing the CASSCF method. To obtain a reliable potential energy profile along the deactivation pathways, the MS-CASPT2 method is employed even for the optimization of minimum energy structures in the excited state and conical intersection (CI) structures between the ground and excited states. In the imino (imino-keto) form, we locate a new CI structure involving the twisting of the imino group, and the decay pathway leading to this CI is found to be barrierless, suggesting a remarkably efficient deactivation of imino cytosine. In the keto (amino-keto) form, the MS-CASPT2 calculations exhibit an efficient decay path to the ethylene-like CI involving the twisting of the C-C double bond in the six-membered ring, with a barrier of similar to 0.08 eV from the minimum of the (1)pi pi(star) state. In the enol (amino-enol) form, three types of CIs are identified for the first time. Among them, the ethylene-like CI with a similar molecular structure to the keto form provides the most preferred deactivation pathway in enol cytosine. This pathway exhibits a higher barrier of similar to 0.22 eV and a higher energy of CI than those of keto cytosine. Nonadiabatic molecular dynamics simulations provide a time-dependent picture of the deactivation processes, including the excited-state lifetime of each tautomer. In particular, the decay time of the imino tautomer is predicted to be only similar to 100 fs. Our computational results are in remarkably good agreement with the experimental findings of recent femtosecond pump-probe photoionization spectroscopy [J. Am. Chem. Soc., 2009, 131, 16939; J. Phys. Chem. A, 2011, 115, 8406], supporting the coexistence of more than one tautomer in the photophysics of isolated cytosine and that each tautomer exhibits a different excited-state lifetime.
  • Derrick Ethelbhert Yu, Akira Kikuchi, Tetsuya Taketsugu, Tamotsu Inabe
    Journal of Chemistry 2013 486318  2013年 [査読有り][通常論文]
     
    Axially-ligated iron phthalocyanines have been found to be good molecular conductors with giant negative magnetoresistance (GNMR) which originates from a strong intramolecular π-d interaction between the metal and phthalocyanine. Ab initio theoretical calculations showed that substitution of ruthenium into the phthalocyanine complex would result in a significant increase in the π-d interaction of the system, potentially intensifying GNMR. This paper presents the crystal preparation and X-ray structural characterization of bis(triphenylphosphine)iminium dichloro(phthalocyaninato(2-))ruthenium(III), PNP [Ru III(Pc 2-)Cl 2]. It is observed that [ Ru III(Pc 2-)Cl 2] system has a symmetric planar RuPc unit with perpendicular axial ligands which results in a unidirectional and uniform solid-state arrangement, suitable for π-d interaction-based molecular conductors with potentially exceptional GNMR. © 2013 Derrick Ethelbhert Yu et al.
  • Satoshi Maeda, Erika Abe, Miho Hatanaka, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 8 12 5058 - 5063 2012年12月 [査読有り][招待有り]
     
    Development of efficient methods for finding chemical reaction pathways has been one of the central subjects of theoretical chemistry. Recently, the artificial force induced reaction (AFIR) method enabled automated search for associative reaction pathways between multiple reactant molecules and has been applied to reactions involving a few tens of atoms. To expand its applicability to large systems, we combined it with the geometrical microiteration technique. With this extension, full optimization of transition state structures of enzymatic reactions in the protein became possible within the QM/MM framework. Performance of the microiteration-AFIR method was tested for a single water catalyzed Aldol reaction in (H2O)(299) cluster and for an enzymatic reaction of the isopenicillin N synthase, where the potential energy surfaces were calculated by the ONIOM(QM/MM) method. These numerical tests demonstrated that the present method is promising in predicting reaction pathways that take place within an active site (consisting of tens of atoms) in a very large environment such as protein and solution.
  • Xue-fang Yu, Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 116 43 10566 - 10573 2012年11月 [査読有り][通常論文]
     
    Excited-state multiple proton transfer (ESMPT) in the cluster of 7-azaindole with three water molecules [7-azaindole(H2O)(3)]is theoretically investigated by the TDDFT, CASPT2, and CC2 methods. Examination of the potential energy surface in the first excited state indicates that ESMPT in 7-azaindole(H2O)(3) proceeds initially with the rearrangement of hydrogen bond structure of water molecules from a bridged-planar isomer to a cyclic-nonplanar isomer, followed by triple proton transfer in the latter. This reaction is found to be energetically more favorable than quadruple proton transfer in the bridged-planar isomer without hydrogen bond reorganization. It is also shown that all proton-transfer processes follow a concerted mechanism rather than a stepwise mechanism. The computational results show good consistency with the unexpected experimental observations as to the electronic spectra and excited-state lifetime. In particular, the barrier of the hydrogen bond rearrangement is found to be less than 1 kcal/mol, consistent with the missing vibronic bands for 7azaindole(H2O)(3) with an excess energy of more than 200 cm(-1) in the SI state.
  • Yu Harabuchi, Akira Nakayama, Tetsuya Taketsugu
    COMPUTATIONAL AND THEORETICAL CHEMISTRY 1000 70 - 74 2012年11月 [査読有り][通常論文]
     
    A concept of trifurcation of a reaction pathway is introduced to analyze the case where a downhill path from the first-order saddle point accompanies three branches via the valley-ridge inflection region, leading to three different product minima on the potential energy surface. We provide a detailed analysis on the reaction path for an electron transfer reaction, HCHO- + CH3Cl -> OH2C-CH3 center dot center dot center dot Cl-, as an illustrative example of the trifurcating reaction path. (C) 2012 Elsevier B.V. All rights reserved.
  • Xue-Fang Yu, Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF COMPUTATIONAL CHEMISTRY 33 20 1701 - 1708 2012年07月 [査読有り][通常論文]
     
    Excited-state double proton transfer (ESDPT) in the (3-methyl-7-azaindole)-(7-azaindole) heterodimer is theoretically investigated by the long-range corrected time-dependent density functional theory method and the complete-active-space second-order perturbation theory method. The calculated potential energy profiles exhibit a lower barrier for the concerted mechanism in the locally excited state than for the stepwise mechanism through the charge-transfer state. This result suggests that the ESDPT in the isolated heterodimer is likely to follow the former mechanism, as has been exhibited for the ESDPT in the homodimer of 7-azaindole. (c) 2012 Wiley Periodicals, Inc.
  • Satoshi Maeda, Tetsuya Taketsugu, Keiji Morokuma
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 3 14 1900 - 1907 2012年07月 [査読有り][通常論文]
     
    To elucidate the photodissociation mechanism of HCOOH, we systematically explored reaction pathways starting from the first excited singlet state (S-1) by using automated reaction path search methods. All critical points, that is, minima, transition states, minimum energy conical intersections, and minima on seam of crossing, for the S-0, T-1, and S-1 potential energy surfaces (PESs) obtained in the present search were optimized at the CASPT2 level. The structure list obtained by the search explained all experimentally reported photolytic channels. A new mechanism for the previously suggested but unexplained conformational memory in the 193 nm photolysis is proposed, which involves two steps: partial dissociation and succeeding roaming of one of H atoms on the S-1 PES, followed by intramolecular recombination on the S-0 PES after radiationless transition through a conical intersection at a partially dissociated geometry. This is partially similar to the excited-state roaming recently discovered for the NO3 radical.
  • Tomokazu Tanaka, Toshiyuki Takayanagi, Tetsuya Taketsugu, Yuriko Ono
    CHEMICAL PHYSICS LETTERS 539 15 - 18 2012年06月 [査読有り][通常論文]
     
    A global three-dimensional potential energy surface for the HeCuF system, which has a relatively large helium binding energy of ca. 6.2 kcal/mol, has been developed using the high-level ab initio CCSD(T) electronic structure method with scalar relativistic effects taken into account. Using the developed potential energy surface, vibrational states of (HeCuF)-He-4 and (HeCuF)-He-3 have been calculated quantum mechanically. Spectroscopic detection of these helium-containing complexes has been discussed. (C) 2012 Elsevier B.V. All rights reserved.
  • Min Gao, Andrey Lyalin, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 116 16 9054 - 9062 2012年04月 [査読有り][通常論文]
     
    The structural, electronic, and catalytic properties of Au and Au-2 supported on the pristine and defected hexagonal boron nitride (h-BN) surface have been studied theoretically using density functional theory. It is demonstrated that adsorption and catalytic activation of O-2 on the h-BN supported Au and Au-2 can be affected by the interaction with the support via electron pushing and donor/acceptor mechanisms. It is shown that even weak interaction of Au and Au-2 with the defect-free "inert" h-BN surface can have an unusually strong influence on the binding and catalytic activation of the molecular oxygen. This effect occurs due to the mixing of the 5d orbitals of the supported Au and Au-2 with the N-p(z) orbitals. Although the defect-free h-BN surface does not act as a good electron donor for the supported O-2-Au, it promotes an electron transfer from the Au to O-2, pushing electrons from the gold to the adsorbed oxygen. In the case of the defected h-BN surface, Au and Au-2 can be trapped effectively by N or B vacancy and impurity point defects. Strong adsorption on the surface defects is accompanied by the large charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported Au and Au-2 can considerably promote their catalytic activity. Therefore, the h-BN surface (pristine or defected) cannot be considered as an inert support for Au and Au-2.
  • Akira Nakayama, Keisuke Niimi, Yuriko Ono, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 136 5 054506  2012年02月 [査読有り][通常論文]
     
    We investigate the vibrational shift of beryllium oxide (BeO) in Xe matrix as well as in Ar matrix environments by mixed quantum-classical simulation and examine the origin of spectral shift in details. BeO is known to form strong chemical complex with single rare gas atom, and it is predicted from the gas phase calculations that vibrational frequencies are blueshifted by 78 cm(-1) and 80 cm(-1) upon formation of XeBeO and ArBeO, respectively. When the effects of other surrounding rare gas atoms are included by Monte Carlo simulations, it is found that the vibrational frequencies are redshifted by 21 cm(-1) and 8 cm(-1) from the isolated XeBeO and ArBeO complexes, respectively. The vibrational shift of XeBeO in Ar matrix is also calculated and compared with experimental data. In all simulations examined in this paper, the calculated vibrational frequency shifts from the isolated BeO molecule are in reasonable agreement with experimental values. The spectral shift due to the rare-gas-complex formation of RgBeO (Rg = Xe or Ar) is not negligible as seen in the previous studies, but it is shown in this paper that the effects of other surrounding rare gas atoms should be carefully taken into account for quantitative description of the spectral shifts and that these two effects are competing in vibrational spectroscopy of BeO in matrix environments. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3680562]
  • Yusuke Ootani, Tetsuya Taketsugu
    JOURNAL OF COMPUTATIONAL CHEMISTRY 33 1 60 - 65 2012年01月 [査読有り][通常論文]
     
    An ab initio molecular dynamics approach is combined with the semiclassical tunneling method of Makri and Miller, which is applied to estimations of tunneling splitting in the umbrella inversion of ammonia and the intramolecular hydrogen transfer in malonaldehyde. In the application to malonaldehyde, effects of multidimensionality are examined by assigning quantum zero-point energies only to significant vibrational modes and changing the amount of energy given to other degrees of freedom. The calculated tunneling splitting values are in good agreement with the corresponding experimental values for both molecules. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 33: 60-65, 2012
  • Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 116 1 491 - 503 2012年01月 [査読有り][通常論文]
     
    The mechanisms of the ultrafast nonradiative deactivation of uracil and its substituted derivatives thymine (5-methyluracil) and 5-fluorouracil after absorption of UV light are explored and compared, by means of ab initio multistate (MS) CASPT2 calculations. The MS-CASPT2 method is applied for the calculation of potential energy profiles, especially for the geometry optimization in the electronically excited state, with the aim of an accurate prediction of deactivation pathways. The resulting,energy curves of each molecule exhibit that the conical intersection between the (1)pi pi* and ground states is accessible via small energy barriers from the minimum in the (1)pi pi* state as well as from that in the (1)n pi* state. The barrier of 5-fluorouracil in the (1)pi pi* state is calculated to be definitely higher than those of uracil and thymine, which is consistent with experiments and suggests that the elongation of the excited-state lifetime of uracil by fluorine substitution is significantly contributed from intrinsic electronic effect of the molecule. However, no evidence of the experimentally observed longer excited-state lifetime of thymine than uracil is found in the presently calculated MS-CASPT2 potential energy curves in the (1)pi pi* and (1)n pi* states, implying nonnegligible contribution of other factors such as solvation effect and substituent mass to the photoinduced dynamics of uracil derivatives.
  • Takumi Nakamura, Satoshi Takeuchi, Tetsuya Taketsugu, Tahei Tahara
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14 18 6225 - 6232 2012年 [査読有り][通常論文]
     
    We report a femtosecond time-resolved fluorescence study of cis-stilbene, a prototypical molecule showing ultrafast olefinic photoisomerization and photocyclization. The time-resolved fluorescence signals were measured in a nonpolar solvent over a wide ultraviolet-visible region with excitation at 270 nm. The time-resolved fluorescence traces exhibit non-single exponential decays which are well fit with bi-exponential functions with time constants of tau(A) = 0.23 ps and tau(B) = 1.2 ps, and they are associated with the fluorescence emitted from different regions of the S-1 potential energy surface (PES) in the course of the structural change. Quantitative analysis revealed that the two fluorescent components exhibit similar intrinsic time-resolved spectra extending from 320 nm to 700 nm with the (fluorescence) oscillator strength of f(A) = 0.32 and f(B) = 0.21, respectively. It was concluded that the first component is assignable to the fluorescence from the untwisted S-1 PES region where the molecule reaches immediately after the initial elongation of the central C=C bond, while the second component is the fluorescence from the substantially twisted region around a shallow S-1 potential minimum. The quantitative analysis of the femtosecond fluorescence data clearly showed that the whole isomerization process proceeds in the one-photon allowed S-1 state, thereby resolving a recent controversy in quantum chemical calculations about the reactive S-1 state. In addition, the evaluated oscillator strengths suggest that the population branching into the isomerization/cyclization pathways occurs in a very early stage when the S-1 molecule still retains a planar Ph-C-C-Ph skeletal structure. On the basis of the results obtained, we discuss the dynamics and mechanism of the isomerization/cyclization reactions of cis-stilbene, as well as the electronic structure of the reaction precursor.
  • Shohei Yamazaki, Tetsuya Taketsugu
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 14 25 8866 - 8877 2012年 [査読有り][通常論文]
     
    Photoinduced processes in the Watson-Crick guanine-cytosine base pair are comprehensively studied by means of long-range corrected (LC) TDDFT calculations of potential energy profiles using the LC-BLYP and CAM-B3LYP functionals. The ab initio CC2 method and the conventional TDDFT method with the B3LYP functional are also employed to assess the reliability of the LC-TDDFT method. The present approach allows us to compare the potential energy profiles at the same computational level for excited-state reactions of the base pair, including single and double proton transfer between the bases and nonradiative decay via ring puckering in each base. In particular, long-range correction to the TDDFT method is critical for a qualitatively correct description of the proton transfer reactions. The calculated energy profiles exhibit low barriers for out-of-plane deformation of the guanine moiety in the locally-excited state, which is expected to lead to a conical intersection with the ground state, as well as for single proton transfer from guanine to cytosine with the well-known electron-driven proton transfer mechanism. Thus the present results suggest that both processes can compete in hydrogen-bonded base pairs and play a significant role in the mechanism of photostability.
  • Min Gao, Andrey Lyalin, Tetsuya Taketsugu
    CATALYSTS 1 1 18 - 39 2011年12月 [査読有り][招待有り]
     
    It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered-the "inert" support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the "active" support of rutile TiO2(110). It is demonstrated that Au and Au-2 can be trapped effectively by the vacancy defects in h-BN. In that case, the strong adsorption on the surface defects is accompanied by the charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported gold clusters can considerably promote their catalytic activity. Therefore gold clusters supported on the defected h-BN surface can not be considered as pseudo-free clusters. We also demonstrate that the rutile TiO2(110) support energetically promotes H-2 dissociation on gold clusters. We show that the formation of the OH group near the supported gold cluster is an important condition for H-2 dissociation. We demonstrate that the active sites towards H-2 dissociation on the supported Au-n are located at corners and edges of the gold cluster in the vicinity of the low coordinated oxygen atoms on TiO2(110). Thus catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support.
  • Yu Harabuchi, Tetsuya Taketsugu
    THEORETICAL CHEMISTRY ACCOUNTS 130 2-3 305 - 315 2011年10月 [査読有り][招待有り]
     
    Appearance of the valley-ridge inflection (VRI) point on the intrinsic reaction path (IRP) introduces geometrical instability of the reaction coordinate and sometimes leads to two different product minima on the potential energy surface (PES). A significant role of the totally symmetric VRI point on the IRP is discussed from the viewpoint of branching of the reaction pathway. As illustrative examples, ab initio calculations were performed to determine the IRP for XCHO(-) + CH(3)Cl (X = H, CH(3)) at the Moller-Plesset second-order perturbation theory (MP2) level with 6-31+G(d) basis sets and geometric features of the PES around the IRP have been analyzed.
  • Akira Nakayama, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 115 32 8808 - 8815 2011年08月 [査読有り][通常論文]
     
    We have investigated the nonradiative deactivation process of malachite green in the singlet excited states, S-1 and S-2 by high-level ab initio quantum chemical calculations using the CASPT2//CASCF approach. The deactivation pathways connecting the Franck-Condon region and conical intersection regions are identified. The initial population in the S-1 state is on a flat surface and the relaxation involves a rotation of phenyl rings, which leads the molecule to reach the conical intersection between the S-1 and S-0 states, where it efficiently decays back to the ground state. There exists a small barrier connecting the Franck-Condon and conical intersection regions on the S-1 potential energy surface. The decay mechanism from the S-2 state also involves the twisting motion of phenyl rings. In contrast to the excitation to the S-1 state, the initial population is on a downhill ramp potential and the barrierless relaxation through the rotation of substituted phenyl rings is expected. During the course of relaxation, the molecule switches to the S-1 state at the conical intersection between S-2 and S-1 and then it decays back to the ground state through the intersection between S-1 and S-0. In relaxation from both S-1 and S-2, large distortion of phenyl rings is required for the ultrafast nonradiative decay to the ground state.
  • Takako Kudo, Tetsuya Taketsugu, Mark S. Gordon
    JOURNAL OF PHYSICAL CHEMISTRY A 115 13 2679 - 2691 2011年04月 [査読有り][通常論文]
     
    The mechanism and dynamics of the formation of a hydrogen molecule by incorporating two hydrogen atoms in a stepwise manner into the cavity of some POSS (polyhedral oligomeric silsesquioxanes) compounds has been investigated by ab initio molecular orbital and ab initio molecular dynamics (AIMD) methods. The host molecules in the present reactions are two types of POSS, T-8 ([HSiO1.5](8)) and T-12(D-2d) ([HSiO1.5](12)). AIMD simulations were performed at the CASSCF level of theory, in which two electrons and two orbitals of the colliding hydrogen atoms are included in the active space. The trajectories were started by inserting the second hydrogen atom into the hydrogen atom-encapsulated-POSS (H + H@T-n -> H-2@T-n; n = 8 and 12). In many cases, the gradual formation of a hydrogen molecule has been observed after frequent collisions of two hydrogen atoms within the cages. The effect of the introduction of an argon atom in T-12 is discussed as well.
  • Ahmed M. El-Nahas, Ahmed H. Mangood, Hikaru Takeuchi, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 115 13 2837 - 2846 2011年04月 [査読有り][通常論文]
     
    The thermochemistry and kinetics of the pyrolysis of 2-butanol have been conducted using ab initio methods (CBS-QB3 and CCSD(T)) and density functional theory (DFT). The enthalpies of formation and bond dissociation energies of some alcohols including 2-butanol and its derived radicals have been calculated. A variety of simple and complex dissociations have been examined. The results indicated that dehydration to 1- and 2-butene through four-center transition states is the most dominant channel at low to moderate temperatures (T <= 700 K), where formation of butenes is kinetically and thermodynamically more favorable than other complex and simple bond scission reactions. Although the C-C bond fission channels require more energy than needed for some complex decomposition reactions, the former pathways predominate at higher temperatures (T >= 800 K) due to the higher values of the pre-exponential factors. The progress of the complex decomposition reactions has been followed through intrinsic reaction coordinate (IRC) calculations to understand the mechanism of transformation of 2-butanol to different products.
  • Xue-fang Yu, Shohei Yamazaki, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL THEORY AND COMPUTATION 7 4 1006 - 1015 2011年04月 [査読有り][通常論文]
     
    Excited-state double proton transfer (ESDPT) in the 7-azaindole dimer is investigated using the complete active space second-order perturbation theory (CASPT2) method and the long-range corrected time-dependent density functional theory (LC-TDDFT) method. These methods are employed for geometry optimizations as well as single-point energy calculations of the excited-state potential energy profiles along the reaction paths. It is shown that three main reaction routes involving double proton transfer exist. In the first route, the ESDPT reaction takes place in the locally excited state through a single transition state following the concerted mechanism in which each proton-transfer process occurs simultaneously without forming any stable zwitterionic intermediate. The concerted ESDPT reaction is found to proceed asynchronously in C-s symmetry rather than synchronously in C-2h symmetry. In the second and third routes, on the other hand, the ESDPT reaction takes place following the stepwise mechanism in which each proton-transfer process occurs sequentially forming a neutral intermediate in the charge-transfer state. The calculated energy profiles of the three routes exhibit a lower barrier in the first route than in the other routes, suggesting that the ESDPT in the gas phase is likely to follow the asynchronous concerted mechanism at the lowest excitation energy.
  • Andrey Lyalin, Tetsuya Taketsugu
    FARADAY DISCUSSIONS 152 185 - 201 2011年 [査読有り][招待有り]
     
    The specific role played by small gold nanoparticles supported on the rutile TiO2(110) surface in the processes of adsorption and dissociation of H-2 is discussed. It is demonstrated that the molecular and dissociative adsorption of H-2 on Lambda u(n) clusters containing n = 1, 2, 8 and 20 atoms depends on cluster size, geometry structure, cluster flexibility and the interaction with the support material. Rutile TiO2(110) support energetically promotes H-2 dissociation on gold clusters. It is demonstrated that the active sites towards H-2 dissociation are located at corners and edges on the surface of the gold nanoparticle in the vicinity of the support. The low coordinated oxygen atoms on the TiO2(110) surface play a crucial role for H-2 dissociation. Therefore the catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support.
  • Andrey Lyalin, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY LETTERS 1 12 1752 - 1757 2010年06月 [査読有り][通常論文]
     
    The molecular and dissociative adorption of O-2 on pure odd-size Au-n, (n = 1,3,5,7,9) clusters and Au-n with a coadsorbed C2H4 molecule has been studied theoretically using density functional theory. It is demonstrated that catalytic activation of the adsorbed O-2 on pure gold clusters in the considered size range cannot lead to O-2 dissociation. Coadsorption of C2H4, however, involves an extra charge transfer from the gold cluster to O-2 energetically promoting oxygen dissociation. Our finding indicates that O-2 dissociation on the surface of small gold clusters in sensitive to the presence of other adsorbates, including the reactant molecule itself. This effect can be particularly important for understanding the mechanism of catalytic oxidation on gold clusters.
  • Manabu Kiguchi, Kunio Hashimoto, Yuriko Ono, Tetsuya Taketsugu, Kei Murakoshi
    PHYSICAL REVIEW B 81 19 195401  2010年05月 [査読有り][通常論文]
     
    The formation of a Pd atomic chain in a hydrogen atmosphere was investigated by measurements of conductance and vibrational spectroscopy of a single molecular junction and the theoretical calculation. While atomic chains were not formed for clean 3d and 4d metals, in the case of Pd (a 4d metal) atomic chains could be formed in the presence of hydrogen. Stable atomic chains with two different atomic configurations were formed when the Pd atomic contact was stretched in a H(2) atmosphere: highly conductive short hydrogen-adsorbed atomic chain and low conductive long hydrogen incorporated atomic chain.
  • Li Sheng, Yuriko Ono, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 114 8 3544 - 3548 2010年03月 [査読有り][通常論文]
     
    The adsorption of Xe on graphene has been systematically investigated by ab initio MP2 calculations Using Dunning's correlation-consistent basis sets. The polycyclic aromatic hydrocarbon (i.e., coronene) is employed to model the graphene surface. The adsorption energies at three high-symmetry sites oil the surface are calculated at the MP2/cc-pVTZ/cc-pVDZ-PP level. Our results show that Xe preferentially occupies the hollow site oil the graphene surface. The equilibrium distance of Xe at the hollow site is calculated as 3.56 angstrom, which is ill excellent agreement with the available experimental value of 3.59 +/- 0.05 angstrom. The corresponding binding energy at the hollow site is calculated as -142.9 meV, whereas the binding energies at the bridge and on-top sites are calculated as -130.8 and -127.4 meV, respectively. The adsorption of polar molecules, XeF and XeBeO, on graphene is also investigated to analyze the site preference.
  • Andrey Lyalin, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 114 6 2484 - 2493 2010年02月 [査読有り][通常論文]
     
    The adsorption of ethylene molecules on neutral, anionic, and cationic gold clusters consisting of up to 10 atoms has been investigated using density functional theory. It is demonstrated that C(2)H(4) can be adsorbed on small gold clusters in two different configurations, corresponding to the pi- and di-sigma-bonded species. Adsorption in the pi-bonded mode dominates over the di-sigma mode over all considered cluster sizes n, with the exception of the neutral C(2)H(4)-Au(5) system. A striking difference is found in the size dependence of the adsorption energy Of C(2)H(4) bonded to the neutral gold clusters in the pi and di-sigma configurations. The important role of the electronic shell effects in the di-sigma mode of ethylene adsorption on neutral gold Clusters is demonstrated. It is shown that the interaction of C(2)H(4) with small gold clusters strongly depends on their charge. The typical shift in the vibrational frequencies of C(2)H(4) adsorbed in the pi and the di-sigma configurations gives a guidance to experimentally distinguish between the two modes of adsorption.
  • Yuriko Taketsugu, Takeshi Noro, Tetsuya Taketsugu
    CHEMICAL PHYSICS LETTERS 484 4-6 139 - 143 2010年01月 [査読有り][通常論文]
     
    Ab initio calculations are performed for noble-gas complexes, Ar-PdCO and Ar-PtCO, by QCISD(T) with a Douglas-Kroll relativistic scheme. The electronic ground states of Ar-PdCO and Ar-PtCO are predicted to be (1)Sigma with linear equilibrium structure, and the binding energy of Ar is estimated as 5.3 and 8.2 kcal/mol for Ar-PdCO and Ar-PtCO, respectively. The M-C-O (M = Pd, Pt) bending frequency in MCO increases by similar to 10% in Ar-MCO. The present calculations suggest that the experimentally reported M-C-O bending frequencies for MCO measured in the solid argon matrix are possibly to be assigned to the overtone band of the M-C-O bending mode of Ar-MCO. (C) 2009 Elsevier B.V. All rights reserved.
  • Yusuke Ootani, Kiminori Satoh, Akira Nakayama, Takeshi Noro, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 131 19 194306  2009年11月 [査読有り][通常論文]
     
    Photoisomerization mechanism of azobenzene in the lowest excited state S-1(n pi(*)) is investigated by ab initio molecular dynamics (AIMD) simulation with the RATTLE algorithm, based on the state-averaged complete active space self-consistent field method. AIMD simulations show that cis to trans isomerization occurs via two-step rotation mechanism, accompanying rotations of the central NN part and two phenyl rings, and this process can be classified into two types, namely, clockwise and counterclockwise rotation pathways. On the other hand, trans to cis isomerization occurs via conventional rotation pathway where two phenyl rings rotate around the NN bond. The quantum yields are calculated to be 0.45 and 0.28 +/- 0.14 for cis to trans and trans to cis photoisomerizations, respectively, which are in very good agreement with the corresponding experimental results.
  • Akira Nakayama, Tetsuya Taketsugu, Motoyuki Shiga
    CHEMISTRY LETTERS 38 10 976 - 977 2009年10月 [査読有り][通常論文]
     
    Efficiency of the ab initio hybrid Monte Carlo and ab initio path integral hybrid Monte Carlo methods is enhanced by employing an auxiliary potential energy surface that is used to update the system configuration via molecular dynamics scheme. As a simple illustration of this method, a dual-level approach is introduced where potential energy gradients are evaluated by computationally less expensive ab initio electronic structure methods.
  • Daisuke Kina, Pooja Arora, Akira Nakayama, Takeshi Noro, Mark S. Gordon, Tetsuya Taketsugu
    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 109 10 2308 - 2318 2009年08月 [査読有り][招待有り]
     
    Ab initio molecular dynamics (AIMD) Simulations are performed to investigate the excited state dynamics of coumarin 151 (C151) in the gas phase and in water solution at the CASSCF level of theory with segmented DZP basis sets, where in the latter case effective fragment potentials (EFP) are used. The dipole moment of an isolated C151 molecule increases considerably upon electronic vertical excitation, from 5.0 D (S-0 state) to 11.1 D (S-1 state). Two equilibrium structures have been identified in the S, state, i.e., a charge-transfer state with a planar amino group and a deformed structure of the six-membered ring with the carbonyl group, and a structure that is similar to the S, equilibrium structure. In AIMD simulations for an isolated C151 molecule (presumably similar to dynamics in nonpolar solvents), C151 decays from S, to S, via a crossing point of the charge-transfer state in some trajectories, while in the AIMD simulations for C151-EFP (including solvent), the S, and S, energies show an almost parallel energy variation with structural changes, and no crossing point is observed. This result is in good agreement with the experimental observation. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 109: 2308-2318, 2009
  • Andrey Lyalin, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY C 113 30 12930 - 12934 2009年07月 [査読有り][通常論文]
     
    The adsorption Of O-2 and C2H4 molecules on small gold clusters consisting of up to 10 atoms has been investigated using theoretical methods based on density-functional theory. It is shown that, in addition to a conventional mechanism of the catalytic activation Of O-2 adsorbed oil a gold cluster, the interaction Of C2H4 with small gold clusters results in considerable weakening of the carbon-carbon double bond. Moreover, coadsorption Of O-2 and C2H4 on small gold clusters with an odd number of atoms leads to cooperative effect which further stabilizes the O-2-Au-N-C2H4 system. Hence, Simultaneous adsorption of the O-2 and C2H4 molecules on free gold clusters can considerably promote the oxidation process via the Langmuir-Hinshelwood mechanism.
  • Hongmei Liu, Wenbin Ni, Jianwei Zhao, Nan Wang, Yan Guo, Tetsuya Taketsugu, Manabu Kiguchi, Kei Murakoshi
    JOURNAL OF CHEMICAL PHYSICS 130 24 244501  2009年06月 [査読有り][通常論文]
     
    In the recent density functional-based calculations, it was found that the conductivity of naphthalene molecular wires can be modulated by altering the linking position of the molecule to the electrode [D. Walter, D. Neuhauser, and R. Baer, Chem. Phys. 299, 139 (2004)]. A quantum interference model was proposed to interpret the observation. In this paper, we further studied the conductance of a series of conjugated molecules containing aromatic rings using density functional theory combined with nonequilibrium Green's function method. For polyacene systems with different terminal connections, the conductivity is dependent on the substitution position of anchoring groups even with similar electron transport distance. The conductance of trans-substitution can be ten times or more as large as that of the cis-substitution. However, for the biphenyl system with different intramolecular connections, adding more connections between two benzene rings does not change the junction conductance. All these results indicate that the junction conductance is strongly dependent on the particular electron transport pathway. The alternating double-single linkage is the most probable one, since others are impeded by the single bonds.
  • Akira Nakayama, Nanami Seki, Tetsuya Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 130 2 024107  2009年01月 [査読有り][通常論文]
     
    An approach is developed to enhance sampling for ab initio Monte Carlo and ab initio path integral Monte Carlo calculations of molecular clusters by utilizing an approximate potential as a guide to move in the configuration space more efficiently. The interpolated potential energy obtained by the moving least-squares method is used as an approximate potential, and this scheme is applied to a water molecule and small protonated water clusters (H(3)O(+), H(5)O(2+)). It is found that the statistical errors are reduced by almost a factor of 3 in most calculations, which translates into a reduction in the computational cost by an order of magnitude. We also provide an automatic scheme where the ab initio data obtained during the simulation is added to the reference data set of interpolation dynamically, which further speeds up the convergence. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3055910]
  • Derrick Ethelbhert C. Yu, Masaki Matsuda, Hiroyuki Tajima, Akira Kikuchi, Tetsuya Taketsugu, Noriaki Hanasaki, Toshio Naito, Tamotsu Inabe
    JOURNAL OF MATERIALS CHEMISTRY 19 6 718 - 723 2009年 [査読有り][通常論文]
     
    A series of one-dimensional conductors, TPP[Fe-III(Pc)L-2](2) with L CN, Cl, and Br, have been prepared. These compounds show giant negative magnetoresistance due to the interaction between conduction pi-electrons and localized Fe-centered d-spins, but the magnitude is found to vary based on the axial ligand, suggesting that the strength of the pi-d interactions is sensitively influenced by the axial substituent. The magnetic susceptibility also shows the difference in the magnetic interactions by the axial substituent. The ab initio calculation of the isolated molecules has revealed that the Jahn-Teller effect in this system induces splitting of d(xz) and d(yz) orbitals, and that the energy shift of the d-orbital accommodating an unpaired electron is varied by the axial substituent. The axial-ligand dependence of the intramolecular pi-d interaction is found to correlate with the magnitude of the magnetoresistance.
  • Haruki Motegi, Akira Kakizaki, Toshiyuki Takayanagi, Yuriko Taketsugu, Tetsuya Takesugu, Motyuki Shiga
    CHEMICAL PHYSICS 354 1-3 38 - 43 2008年12月 [査読有り][通常論文]
     
    Path-integral molecular dynamics simulations have been performed to understand the quantum helium solvation structures in the He(n)BeO cluster up to n = 100. Our simulations show that one helium atom is strongly bound to BeO to form HeBeO and that the first solvation shell around the HeBeO complex includes roughly 12-14 helium atoms. The second solvation Structure was also observed for it > 20. Both the first and second solvation shells show an anisotropic behavior but the anisotropy for the second solvation shell Was found to be Much weaker than that for the first solvation shell, as expected. The present simulations Suggest that the HeBeO complex may be formed in large helium Clusters. (C) 2008 Elsevier B.V. All rights reserved.
  • Satoshi Takeuchi, Sanford Ruhman, Takao Tsuneda, Mahito Chiba, Tetsuya Taketsugu, Tahei Tahara
    SCIENCE 322 5904 1073 - 1077 2008年11月 [査読有り][通常論文]
     
    Understanding a chemical reaction ultimately requires the knowledge of how each atom in the reactants moves during product formation. Such knowledge is seldom complete and is often limited to an oversimplified reaction coordinate that neglects global motions across the molecular framework. To overcome this limit, we recorded transient impulsive Raman spectra during ultrafast photoisomerization of cis- stilbene in solution. The results demonstrate a gradual frequency shift of a low- frequency spectator vibration, reflecting changes in the restoring force along this coordinate throughout the isomerization. A high- level quantum- chemical calculation reproduces this feature and associates it with a continuous structural change leading to the twisted configuration. This combined spectroscopic and computational approach should be amenable to detailed reaction visualization in other photoisomerizing systems as well.
  • Daisuke Kina, Akira Nakayama, Takeshi Noro, Tetsuya Taketsugu, Mark S. Gordon
    JOURNAL OF PHYSICAL CHEMISTRY A 112 40 9675 - 9683 2008年10月 [査読有り][通常論文]
     
    Ab initio molecular dynamics (AIMD) simulations for the excited-state hydrogen transfer (ESHT) reaction of 7-azaindole (7AI-(H2O)(n); n = 1, 2) clusters in the gas phase and in water are presented. The effective fragment potential (EFP) is employed to model the surrounding water molecules. The AIMD simulations for 7AI-H2O and 7AI-(H2O)(2) clusters show an asynchronous hydrogen transfer at t similar to 50 fs after the photoexcitation. While the ESHT mechanism for 7AI-H2O in water does not change appreciably compared with that in the gas phase, the AIMD simulations on 7AI-(H2O)(2) in water solution exhibit two different mechanisms. Since the tautomer form is lower in energy compared to the normal form in the S, state, 7AI and (H2O)(n) fragments separate from each other after the ESHT. With the use of the results of the AIMD trajectories, the minimum energy conical intersection point in the tautomer region has also been located.
  • Kayanuma Megumi, Taketsugu Tetsuya, Ishii Keisaku
    Theoretical Chemistry Accounts 120 1-3 191 - 198 Springer 2008年05月 [査読有り][招待有り]
     
    An ab initio molecular dynamics simulations have been carried out for the dissociative recombination reaction of the deuterium-substituted hydronium cation, HD2O+ + e(-), at the state-averaged multiconfigurational self-consistent field level. In the present simulations, five electronic states of HD2O were included explicitly, and non-adiabatic transitions among adiabatic electronic states were taken into account by the Tully's fewest switches algorithm. It is shown that the dominant products, OD + D + H, were generated in 63% of trajectories, while the products, OH + 2D, were generated in o...
  • Toshiyuki Takayanagi, Haruki Motegi, Yuriko Taketsugu, Tetsuya Taketsugu
    CHEMICAL PHYSICS LETTERS 454 1-3 1 - 6 2008年03月 [査読有り][通常論文]
     
    A three-dimensional global potential energy surface for the simple helium-containing complex HeBeO is developed at a highly-accurate CASPT2 ab initio level with large basis sets. Both time-dependent and time-independent quantum dynamics calculations have subsequently been performed to obtain wavefunctions of bound vibrational states as well as resonance states on the newly developed potential surface. It has been found that the system has more than 10 bound vibrational states even for zero total angular momentum. Quantum number assignment for the obtained vibrational states is also given. (c) 2008 Elsevier B. V. All rights reserved.
  • Yuriko Taketsugu, Takeshi Noro, Tetsuya Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 112 5 1018 - 1023 2008年02月 [査読有り][通常論文]
     
    Ar-NiCO and Ne-NiCO have been predicted as novel neutral noble gas charge-transfer complexes, with binding energies of 7.70 and 2.16 kcal/mol, respectively, by the highly correlated coupled-cluster singles and doubles including a perturbational estimate of triple excitations calculations. The calculated shifts in the Ni-C-O bending frequency are 48 and 36 cm(-1) for Ar-NiCO and Ne-NiCO, while the corresponding experimental matrix shifts are 46 and 36 cm(-1), respectively. The anharmonicity effects for these frequencies are verified to be very small. The interaction between a noble gas atom and NiCO is discussed through natural population analyses and the electron density difference map. We further examined the noble gas matrix effects on the geometrical structure and vibrational frequencies of NiCO by performing density functional theory calculations for the Ng(31)-NiCO (Ng = At, Ne, He) system. The present results will inspire the further experimental investigation on the complexes of noble gas and transition metal compounds generated in the matrix isolation experiments.
  • Keisaku Ishii, Tetsuya Taketsugu, Koichi Yamashita
    JOURNAL OF CHEMICAL PHYSICS 127 19 194307  2007年11月 [査読有り][通常論文]
     
    The potential energy curves for the lowest (3)Sigma(-), (3)Pi, and (5)Sigma(-) states of the KN molecule have been calculated by the multireference singles and doubles configuration interaction method, including Davidson's corrections for quadruple excitations [MRCI(+Q)]. It is shown that the former two are bound, while the last one is repulsive. The electronic ground state of KN is predicted as (3)Sigma(-) state, although the term energy of the (3)Pi state is very small, 177.3 cm(-1). The binding energy for the (3)Sigma(-) state is evaluated as 0.838 eV, the rotational constant B-0 as 0.250 63 cm(-1), and harmonic frequency as 324.4 cm(-1). The spin-orbit coupling effects between the (3)Sigma(-) and (3)Pi states of KN are evaluated and discussed. The same MRCI(+Q) computational procedures are applied to the isovalent LiN, KC, KO, and KCl to confirm the accuracy of present calculations. Theoretical spectroscopic constants presented here will inspire experimental studies of KN. (c) 2007 American Institute of Physics.
  • Toshiyuki Takayanagi, Tomoko Asakura, Kenta Takahashi, Yuriko Taketsugu, Tetsuya Taketsugu, Takeshi Noro
    CHEMICAL PHYSICS LETTERS 446 1-3 14 - 19 2007年09月 [査読有り][通常論文]
     
    The simplest metastable Xe-containing compound HXeH has been theoretically investigated using highly-accurate CASPT2-level electronic structure calculations taking the relativistic effects into account. A new three-dimensional global potential energy surface has been developed and time-dependent wave packet quantum dynamics calculations were then performed to obtain vibrational energy levels of the metastable states for the HXeH, HXeD and DXeD systems. It has been found that low-lying vibrational states below and just above the H + Xe + H dissociation limit have extremely long lifetimes in a nanosecond time scale. The present theoretical results suggest that these rare-gas containing molecules can experimentally be detected in the gas phase. (C) 2007 Elsevier B.V. All rights reserved.
  • Valerie Rodriguez-Garcia, So Hirata, Kiyoshi Yagi, Kimihiko Hirao, Tetsuya Taketsugu, Igor Schweigert, Mitsuo Tasumi
    JOURNAL OF CHEMICAL PHYSICS 126 12 124303  2007年03月 [査読有り][通常論文]
     
    The authors present a first-principles prediction of the energies of the eight lowest-lying anharmonic vibrational states of CO2, including the fundamental symmetric stretching mode and the first overtone of the fundamental bending mode, which undergo a strong coupling known as Fermi resonance. They employ coupled-cluster singles, doubles, and (perturbative) triples [CCSD(T) and CCSDT] in conjunction with a range of Gaussian basis sets (up to cc-pV5Z, aug-cc-pVQZ, and aug-cc-pCVTZ) to calculate the potential energy surfaces (PESs) of the molecule, with the errors arising from the finite basis-set sizes eliminated by extrapolation. The resulting vibrational many-body problem is solved by the vibrational self-consistent-field and vibrational configuration-interaction (VCI) methods with the PESs represented by a fourth-order Taylor expansion or by numerical values on a Gauss-Hermite quadrature grid. With the VCI, the best theoretical estimates of the anharmonic energy levels agree excellently with experimental values within 3.5 cm(-1) (the mean absolute deviation). The theoretical (experimental) anharmonic frequencies of the Fermi doublet are 1288.9 (1285.4) and 1389.3 (1388.2) cm(-1). (c) 2007 American Institute of Physics.
  • Yuriko Taketsugu, Tetsuya Taketsugu, Takeshi Noro
    JOURNAL OF CHEMICAL PHYSICS 125 15 154308  2006年10月 [査読有り][通常論文]
     
    Following our recent study on Ng-Pt-Ng (Ng=Ar,Kr,Xe) [J. Chem. Phys. 123, 204321 (2005)], the binding of noble-gas atoms with Pd atom has been investigated by the ab initio coupled cluster CCSD(T) method with counterpoise corrections, including relativistic effects. It is shown that two Ng atoms bind with Pd atom in linear geometry due to the s-d(sigma) hybridization in Pd where the second Ng atom attaches with much larger binding energy than the first. The binding energies are evaluated as 4.0, 10.2, and 21.5 kcal/mol for Ar-Pd-Ar, Kr-Pd-Kr, and Xe-Pd-Xe, respectively, relative to the dissociation limit, Pd (S-1)+2Ng. In the hybrid Ng complexes, the binding energies for XePd and Ng (=Ar,Kr) are evaluated as 4.0 and 6.9 kcal/mol for XePd-Ar and XePd-Kr, respectively. The fundamental frequencies and low-lying vibrational-rotational energy levels are determined for each compound by the variational method, based on the three-dimensional near-equilibrium potential energy surface. Results of vibrational-rotational analyses for Ng-Pt-Ng (Ng=Ar,Kr,Xe) and Xe-Pt-Ng (Ng=He,Ne,Ar,Kr) compounds are also given. (c) 2006 American Institute of Physics.
  • Keisaku Ishii, Tetsuya Taketsugu, Koichi Yamashita
    CHEMICAL PHYSICS LETTERS 427 1-3 1 - 4 2006年08月 [査読有り][通常論文]
     
    Potential energy curves for the lowest (3)Sigma(-) (3)Pi, (1)Delta, and (5)Sigma(-) states of NaN have been calculated by the multireference singles and doubles configuration interaction method, including Davidson's correction for quadruple excitations (MR-SDCI(+Q). It is shown that the former three are bound states, while the last one has no minimum. The ground state of NaN is predicted to be (3)Sigma(-) for which the binding energy is evaluated as 0.859 eV, and the rotational constants are calculated as B-e = 11.632 and B-0 = 11.558 GHz. The spectroscopic constants presented here will help in the detection of NaN in interstellar space. (c) 2006 Elsevier B.V. All rights reserved.
  • C Oyanagi, K Yagi, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 124 6 64311  2006年02月 [査読有り][通常論文]
     
    Full-dimensional ab initio potential-energy surface (PES) and dipole moment surface are constructed for a methane molecule at the CCSD(T)/cc-pVTZ and MP2/cc-pVTZ levels of theory, respectively, by the modified Shepard interpolation method based on the fourth-order Taylor expansion [MSI(4th)]. The reference points for the interpolation have been set in the coupling region of CH symmetric and antisymmetric stretching modes so as to reproduce the vibrational energy levels related to CH stretching vibrations. The vibrational configuration-interaction calculations have been performed to obtain the energy levels and the absorption intensities up to 9000 cm(-1) with the use of MSI(4th)-PES. The calculated fundamental frequencies and low-lying vibrational energy levels show that MSI(4th) is superior to the widely employed quartic force field, giving a better agreement with the experimental values. The absorption bands of overtones as well as combination bands, which are caused by purely anharmonic effects, have been obtained up to 9000 cm(-1). Strongly coupled states with visible intensity have been found in the 6500-9000 cm(-1) region where the experimental data are still lacking.
  • M Kayanuma, T Taketsugu, K Ishii
    CHEMICAL PHYSICS LETTERS 418 4-6 511 - 518 2006年02月 [査読有り][通常論文]
     
    The dissociative recombination of H3O+ has been studied by the ab initio direct trajectory simulations at the state-averaged complete active space self-consistent field level to investigate tendency in the branching ratios of the dissociative products. Five electronic states of H3O including two Rydberg states have been taken into account in the simulations, and nonadiabatic transitions among adiabatic states were taken into account by the Tully's fewest switches algorithm. It is verified that the highest energy products, OH + 2H. were generated in 87% of trajectories, while the most exothermic products, H2O + H, were generated in 10% of trajectories. (c) 2005 Elsevier B.V. All rights reserved.
  • K Ishii, A Tajima, T Taketsugu, K Yamashita
    ASTROPHYSICAL JOURNAL 636 2 927 - 931 2006年01月 [査読有り][通常論文]
     
    In order to elucidate the unusually high [HNC]/[ HCN] abundance ratio observed in interstellar space, we have carried out wave packet simulations for the dissociative recombination reaction HCNH+ + e(-) -> HNC/HCN + H on the two-dimensional potential energy surfaces (PESs) of two dissociative electronic states of HCNH, 1 (2)Sigma(+) and 2 (2)Sigma(+). Two adiabatic PESs of 1 (2)Sigma(+) and 2 (2)Sigma(+) have been determined as functions of NH and CH bond lengths for a linear geometry of HCNH with a fixed CN bond length, by the multireference single and double configuration interaction plus Davidson's quadruple excitation correction [MR-SDCI(+Q)] method. The wave packets, generated from the low-lying vibrational eigenstates of HCNH+, have been put initially on the 2(2)Sigma(+) adiabatic PES. The resulting branching ratios of [ HNC]/[ HCN] vary from 0.77 to 1.32, depending on the initial vibrational quantum numbers, which support that HCNH+ is the precursor of both HNC and HCN in interstellar space.
  • T Takayanagi, T Taketsugu
    CHEMICAL PHYSICS LETTERS 417 1-3 143 - 148 2006年01月 [査読有り][通常論文]
     
    Nonadiabatic transitions through spin-orbit interaction for the C(P-3(J)) + H-2(B-2(1)) reaction were investigated by ab initio electronic structure calculations and quantum reactive scattering calculations. It has been found that the reactivity for the J = 0 and J = 1 states is quite large. Ab initio direct trajectory calculations oil the lowest doublet potential energy surface have also been carried out in order to understand the HNC production mechanism. We have found that HNC is mostly produced via direct mechanism, in which the H elinlination occurs directly from the CNH2 intermediate, initially formed by the addition of C to NH2. (c) 2005 Elsevier B.V. All rights reserved.
  • Keisaku Ishii, Tetsuya Taketsugu
    The Astrophysical Journal 634 2 L201 - L204 2005年12月 [査読有り][通常論文]
     
    Spectroscopic constants for the lowest 2 ∑, 4 ∑ - , 2 ∑ - , and 4 ∑ states of the CaN radical have been calculated by the multireference singles and doubles configuration interaction method, including Davidson's correction for quadruple excitations [MR-SDCI(+Q)], to aid in detection of the first Ca-bearing molecule in interstellar space. It is shown that the 2 ∏ state is the ground state of CaN and that the 4 ∑ - state is the first excited state, although their energy difference is very small (∼493.4 cm -1 ). This result is contrary to that for the isovalent species MgN. The calculated rotational constants for the 2 ∑ state are B e = 10.767 GHz and B 0 = 10.731 GHz, while those for the 4 ∑ - state are B e = 9.3807 GHz and B 0 = 9.3373 GHz. © 2005. The American Astronomical Society. All rights reserved.
  • Y Ono, T Taketsugu, T Noro
    JOURNAL OF CHEMICAL PHYSICS 123 20 204321  2005年11月 [査読有り][通常論文]
     
    We have investigated the binding of noble-gas (Ng) atoms (Ng=Ar,Kr,Xe) with Pt atom by the ab initio coupled-cluster CCSD(T) method, taking into account the relativistic effects. It is shown that two Ng atoms can bind with Pt atom in linear geometry in the singlet lowest state where the second Ng atom attaches to Pt with the larger binding energy than the first Ng atom. The binding energy is evaluated as 8.2, 17.9, and 33.4 kcal/mol for Ar-Pt-Ar, Kr-Pt-Kr, and Xe-Pt-Xe, respectively, relative to the triplet ground state of the dissociation limit Pt (D-3)+2Ng. The present results indicate that these Ng-Pt-Ng compounds are possible new gas-phase or matrix species. (c) 2005 American Institute of Physics.
  • T Taketsugu, K Yagi, MS Gordon
    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY 104 5 758 - 772 2005年09月 [査読有り][招待有り]
     
    Vibrational frequencies for the 7-azaindole and 7-azaindole-water complex are calculated by the vibrational self-consistent field (VSCF) and correlation-corrected VSCF (cc-VSCF) methods using second-order perturbation theory (MP2), with the 6-31G(d) basis set, and density functional theory with the B3LYP functional and the same basis set. The potential energies at quadrature points for VSCF calculations are estimated from the quartic force field (QFF) determined by the respective electronic structure methods. The comparison with experimental fundamentals for 7-azaindole indicates that MP2 gives better results for NH and CH stretching modes than B3LYP, while B3LYP gives better results for CC stretching and ring deforming modes. The vibrational modes for the 7-azaindole-water complex are discussed in terms of those of the isolated 7-azaindole and water. This VSCF/QFF approach will help quantitative evaluations of vibrational energies of a general polyatomic molecule with a reasonable computational cost. (c) 2005 Wiley Periodicals, Inc.
  • M Takahashi, Y Watanabe, T Taketsugu, DJ Wales
    JOURNAL OF CHEMICAL PHYSICS 123 4 044302  2005年07月 [査読有り][通常論文]
     
    Tunneling splittings in the water trimer have been determined by the semiclassical WKB method, based on pathways characterized at the computational level of second-order Moller-Plesset theory with basis sets of aug-cc-pVTZ quality. This calculation takes into account the single-flip and bifurcation tunneling rearrangements of the water trimer. The predicted splittings are 37.93 cm(-1) for the flip and 6.50x10(-3) cm(-1) for bifurcation, which agree quite well with the corresponding experimental values of 43.52 cm(-1) and 9.63x10(-3) cm(-1). (C) 2005 American Institute of Physics.
  • Y Ono, T Taketsugu
    MONATSHEFTE FUR CHEMIE 136 6 1087 - 1106 2005年06月 [査読有り][通常論文]
     
    Ab initio multireference and coupled cluster methods (MR-SDCI(+Q), CASPT2, CCSD(T)) and density functional theory methods (B3LYP, MPWPW91) have been applied to examine geometrical structures and vibrational frequencies of noble gas (Ng) - transition metal compounds, Ng-NiCO, Ng-NiN2, and Ng-CoCO (Ng = He, Ne, Ar, Kr, Xe). It is shown that the respective compounds can have a larger binding energy than a typical van der Waals interaction energy. The binding mechanism is explained by a partial electron transfer from a noble gas atom to the low-lying 4s and 3d vacant orbitals of the transition metal atom. Theoretical calculations show that the binding of noble gas atom results in a large shift of the bending frequency: 361.1 cm(-1) (NiCO) to 403.5 cm(-1) (Ar-NiCO); 308.5 cm(-1) (NiN2) to 354.8 cm(-1) (Ar-NiN2); 373.0 cm(-1) (CoCO) to 422.6 cm(-1) (Ar-CoCO). The corresponding experimental frequencies determined in solid argon are 409.1 cm(-1) (NiCO), 357.0 cm(-1) (NiN2), and 424.9 cm(-1) (CoCO), which are much closer to the corresponding frequency of Ar-NiCO, Ar-NiN2, and Ar-CoCO, respectively.
  • K Ishii, T Taketsugu
    ASTROPHYSICAL JOURNAL 626 1 L33 - L35 2005年06月 [査読有り][通常論文]
     
    Spectroscopic constants for the lowest (4)&USigma;(-) and (2)&UPi; states of the MgN radical have been calculated by the multireference singles and doubles configuration interaction method, including Davidson's correction for quadruple excitations [MR-SDCI(+Q)]. It is shown that the (4)&USigma;(-) state is the ground state of MgN and that the (2)&UPi; state is the first excited state, lying 6.5 kcal mol(-1) higher in energy. The binding energy for the X (4)&USigma;(-) state is evaluated as 11.1 kcal mol(-1), and the rotational constants are B-e = 13.357 and B-0 = 13.259 GHz. The spectroscopic constants presented here will help in the detection of the MgN radical in interstellar space.
  • T Takayanagi, M Shiga, T Taketsugu
    JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 4 1 197 - 207 2005年03月 [査読有り][招待有り]
     
    High-quality ab initio electronic structure calculations for the van der Waals interaction of He with Cl-2 in the electronic ground state have been carried out to develop a new three-dimensional potential energy surface for this system. The calculations were performed at the single and double excitation coupled-cluster level of theory with non-iterative perturbational treatment of triple excitations [CCSD(T)] with a very large basis set including an additional set of bond functions. The analytical potential surface developed were then used in the path-integral molecular dynamics calculations for the HenCl2 cluster, where quantum solvation structures of helium atoms in clusters were investigated. It has been found that the helium solvation structures are quite different between the electronic ground state and the electronically excited B(3)Pi state.
  • K Yagi, GV Mil'nikov, T Taketsugu, K Hirao, H Nakamura
    CHEMICAL PHYSICS LETTERS 397 4-6 435 - 440 2004年10月 [査読有り][通常論文]
     
    Tunneling splitting of the vibrational ground state is calculated for a planar model of malonaldehyde by the instanton method of Mil'nikov and Nakamura with use of ab initio potential energy surface. The planar model gives much larger tunneling splitting than the previous full dimensional calculations, indicating a strong effect of the anharmonic coupling between the in-plane and out-of-plane modes. The anharmonicity is related to the Coriolis coupling between the OH stretching vibration and the pseudo-rotation of the hindered rotor. The present results suggest that the multidimensional effects should be carefully taken into account in the tunneling dynamics of polyatomic molecules. (C) 2004 Elsevier B.V. All rights reserved.
  • M Yano, T Taketsuga, K Hori, H Okamoto, S Takenaka
    CHEMISTRY-A EUROPEAN JOURNAL 10 16 3991 - 3999 2004年08月 [査読有り][通常論文]
     
    The series of alkyl 4-[2-(perfluorooctyl)ethoxy]benzoates (F8-n) shows a systematic change of crystal structures depending on the length of the alkyl chain: separate packing of perfluorooctyl (R-f) and alkyl (R-h) chains from each other for shorter (n=2) and longer (n=11) members, alternate packing of R-f and R-h chains for middle (n=6,7) members, and an intermediate type of packing for n=4. Semiempirical MO calculations show slightly repulsive interactions between the R-f chains, and attractive ones between R-f and R-h chains and between R-h and the core of a molecular pair. It is concluded that fluorination determines the molecular shape of the crystal structures by making the chain rigid. It is confirmed that the interactions between R-f chains are small compared with those between other moieties and that they are forced to aggregate owing to the exclusion from other moieties. Thus, the effect is dependent on the geometries and intermolecular interactions of the other moieties.
  • K Yagi, K Hirao, T Taketsugu, MW Schmidt, MS Gordon
    JOURNAL OF CHEMICAL PHYSICS 121 3 1383 - 1389 2004年07月 [査読有り][通常論文]
     
    For polyatomic molecules, n-mode coupling representations of the quartic force field (nMR-QFF) are presented, which include terms up to n normal coordinate couplings in a fourth-order polynomial potential energy function. The computational scheme to evaluate third-and fourth-order derivatives by finite differentiations of the energy is fully described. The code to generate the nMR-QFF has been implemented into GAMESS program package and interfaced with the vibrational self-consistent field (VSCF) and correlation corrected VSCF (cc-VSCF) methods. As a demonstration, fundamental frequencies have been calculated by the cc-VSCF method: based on 2MR-QFF for formaldehyde, ethylene, methanol, propyne, and benzene. The applications show that 2MR-QFF is a highly accurate potential energy function, with errors of 1.0-1.9% relative to the experimental value in fundamental frequencies. This approach will help quantitative evaluations of vibrational energies of a general molecule with a reasonable computational cost. (C) 2004 American Institute of Physics.
  • K Yagi, T Takayanagi, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 120 22 10395 - 10403 2004年06月 [査読有り][通常論文]
     
    The effect of nonadiabatic transitions through the spin-orbit couplings has been investigated on the fast neutral reaction, O(P-3)+CH3-->CH3O. Adiabatic potential energies and the spin-orbit coupling terms have been evaluated for the four electronic states of CH3O (E-2, (2)A(2), E-4, and (4)A(2)) that correlate with the O(P-3)+CH3 asymptote, as a function of CO distance and OCH angle under the C-3v symmetry, by ab initio electronic structure calculations using multireference internally contracted single and double excitation configuration interaction method with the 6-311G(2df,2pd) basis sets. Multistate quantum reactive scattering calculations have been carried out with the use of thus obtained potential energies and spin-orbit coupling matrices, based on the generalized R-matrix propagation method. The calculated thermal rate constants show a slight positive dependence on temperature in a range between 50 and 2000 K, supporting the previous experimental results. It is shown that the spin-orbit coupled excited states give rise to reflections over the centrifugal barrier due to the quantum interference. Classical capture calculations yield larger rate constants due to the neglect of quantum reflections. It is concluded that the effect of nonadiabatic transitions is of minor importance on the overall reactivity in this reaction. (C) 2004 American Institute of Physics.
  • Tetsuya Taketsugu, Asami Tajima, Keisaku Ishii, Tsuneo Hirano
    The Astrophysical Journal 608 1 323 - 329 2004年06月 [査読有り][通常論文]
     
    The dissociative recombination reaction of HCNH + + e - via indirect radiative mechanism on relevant excited state potential energy surfaces has been studied to investigate the branching ratio of the products, HNC/HCN, by using an ab initio direct trajectory method at the state-averaged multiconfigurational self-consistent field level. In trajectory simulations using adiabatic potential energy surfaces, nonadiabatic transitions among the three electronic states of HCNH, i.e., 1 2 Π, 1 2 Σ + , and 2 2 Σ + , were explicitly treated by Tully's surface-hopping algorithm. We show that HNC and HCN are produced with almost the same ratio from this reaction, supporting the picture that HCNH + plays a significant role as the precursor for both HNC and HCN production in interstellar clouds.
  • Y Ono, T Taketsugu
    JOURNAL OF PHYSICAL CHEMISTRY A 108 25 5464 - 5467 2004年06月 [査読有り][通常論文]
     
    It is shown that Ar combines with CoCO (X (2)Delta) with the binding energy of 7.18 kcal/mol (CASPT2), 6.25 kcal/mol (RCCSD(T)), and 5.05 kcal/mol (UMPWPW91) in which a counterpoise correction and zero-point vibrational energy correction have been included. The Co-C-O bending frequency has been calculated, by the UMPWPW91 method, as 373.0 and 422.9 cm(-1) for CoCO and Ar-CoCO, respectively, the latter of which is in good agreement with the corresponding experimental frequency, 424.9 cm(-1), determined for CoCO isolated in solid argon.
  • Y Watanabe, T Taketsugufoot, DJ Wales
    JOURNAL OF CHEMICAL PHYSICS 120 13 5993 - 5999 2004年04月 [査読有り][通常論文]
     
    Tunneling splittings in the water dimer have been determined by the semiclassical WKB method, based on pathways characterized at the computational level of second-order Moller-Plesset (MP2) theory with basis sets of aug-cc-pVTZ quality. This calculation takes into account all three acceptor tunneling, donor-acceptor interchange, and bifurcation tunneling rearrangements of the water dimer. The tunneling splittings were evaluated as 7.73 cm(-1) (large splitting) and 0.42 cm(-1) (small splitting), which are in good agreement with the corresponding experimental values of 11.18 cm(-1) and 0.70 cm(-1), respectively. (C) 2004 American Institute of Physics.
  • Y Ono, T Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 120 13 6035 - 6040 2004年04月 [査読有り][通常論文]
     
    It is shown that NiN2 and noble gas atoms, Ar, Ne, and He, combine with the binding energy of 11.52, 4.06, and 7.37 kcal/mol, respectively, by the multireference perturbational (CASPT2) method. By the density functional theory calculations using MPWPW91 functionals, the Ni-N-N bending frequency in NiN2 and Ar-NiN2 is estimated as 310.7 and 358.7 cm(-1), respectively, the latter of which is in good agreement with the corresponding experimental frequency, 357.0 cm(-1), determined for NiN2 isolated in solid argon. (C) 2004 American Institute of Physics.
  • GV Mil'nikova, K Yagi, T Taketsugu, H Nakamura, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 120 11 5036 - 5045 2004年03月 [査読有り][通常論文]
     
    A practical and accurate semiclassical method for calculating the tunneling splitting of the ground state in polyatomic molecules is presented based on a recent version of the instanton theory [J. Chem. Phys. 115, 6881 (2001)]. The method uses ab initio quantum chemical data for the potential energy surface without any concomitant extrapolation and requires only a small number of ab initio data points to get convergence even for large molecules. This enables one to use an advanced level of electronic structure theory and achieve a high accuracy of the result. The method is applied to the 9-atomic malonaldehyde molecule by making use of the potential energy surface at the level of CCSD(T) with the hybrid basis set of aug-cc-pVTZ (for oxygen atoms and the transferred hydrogen atom) and cc-pVTZ (for other atoms). (C) 2004 American Institute of Physics.
  • Y Ono, T Taketsugu
    CHEMICAL PHYSICS LETTERS 385 1-2 85 - 91 2004年02月 [査読有り][通常論文]
     
    It was shown that nickel monocarbonyl and noble gas atoms, Ar, Ne, and He combine with the binding energy of 9.55, 3.71, and 5.97 kcal/mol, respectively, at the CCSD(T) level. The fundamental for Ni-C-O bending frequency in Ar-NiCO was estimated as 454.3 cm(-1) which is largely shifted from the corresponding value for NiCO, 418.6 cm(-1). It was discussed whether the experimental fundamentals for NiCO in argon matrix should be attributed to NiCO or Ar-NiCO. (C) 2003 Elsevier B.V. All rights reserved.
  • K Sato, B Klotz, T Taketsugu, T Takayanagi
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 6 15 3969 - 3976 2004年 [査読有り][通常論文]
     
    The rate coefficients for the reactions of O-3 with six unsaturated carbonyls have been measured with the relative-rate method in the presence of a sufficient radical scavenger. The experiments were conducted using a 6-m(3) reaction chamber combined with a long-path FTIR system. The rate coefficients (measured in 10(-18) cm(3) molecule(-1) s(-1)) were 1.58+/-0.23 for crotonaldehyde, 1.59+/-0.22 for trans-2-pentenal, 1.82+/-0.26 for 3-methyl-2-butenal, 5.34+/-0.73 for trans-2-methyl-2-butenal, 29.5+/-4.1 for 3-pentene-2-one and 8.3+/-1.1 for mesityl oxide. Conventional transition-state theory (CTST) calculations based on ab initio molecular orbital and density functional methods were performed to evaluate the rate constants for nine unsaturated carbonyls including six compounds examined in the present experiment as well as acrolein, methacrolein, and methyl vinyl ketone. A log-log plot of the rate coefficients measured in the present and previous works vs. the calculated results of the rate constants, showed a linear relationship.
  • Tetsuya Taketsugu, Keisaku Ishii, Stuart Carter
    Chemical Physics Letters 380 1-2 213 - 222 2003年10月 [査読有り][通常論文]
     
    The spin-rovibronic spectrum of the à 2 Π←X̃ 2 Σ + electronic transition of MgNC has been determined variationally by RVIB3 [Mol. Phys. 98 (2000) 1697], based on the three-dimensional near-equilibrium potential energy surfaces of the 1 2 A ′ , 2 2 A ′ and 1 2 A″ states together with the transition moment functions between these electronic states. The theoretically determined spectrum is shown to be in very good agreement with the corresponding gas-phase high-resolution experimental spectrum. © 2003 Elsevier B.V. All rights reserved.
  • GV Mil'nikov, K Yagi, T Taketsugu, H Nakamura, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 119 1 10 - 13 2003年07月 [査読有り][通常論文]
     
    We report an accurate and efficient full dimensional semiclassical ab initio method for calculation of energy level splitting due to tunneling in polyatomic system. The method is applied to 21-dimensional 9-atomic malonaldehyde molecule. The tunneling splittings obtained are DeltaE(H) 521.2 cm(-1) for hydrogen atom transfer and DeltaE(D) 53.0 cm(-1) for deuterium atom transfer, which are in excellent agreement with the experimental values of 21.6 cm(-1) and, 2.9 cm(-1) respectively. We believe that the present analysis gives the final solution to the longstanding problem. (C) 2003 American Institute of Physics.
  • K Ishii, T Taketsugu, T Hirano
    CHEMICAL PHYSICS LETTERS 374 5-6 506 - 512 2003年06月 [査読有り][通常論文]
     
    The potential energy surfaces of CaNC ((X) over tilde (2)Sigma(+)) and CaCN ((X) over tilde (2)Sigma(+)) have been investigated by the highly correlated ab initio molecular orbital methods. The bending potential for CaNC is shallow, and shows quite anharmonic and anomalous character, which can explain why the centrifugal distortion constants up to the tenth order were required for the analysis of its rotational spectrum. The reaction path for the isomerization reaction of CaNC and CaCN was also determined: The activation barrier is 2111 cm(-1) from the CaNC side, and 602 cm(-1) from the CaCN side. Core-core and core-valence correlation contributions of Ca M-shell electrons make the Ca-N (for CaNC) and Ca-C (for CaCN) bond lengths shorter by 0.05 and 0.04 Angstrom, respectively, which indicates the significance of these core-correlation effects. (C) 2003 Elsevier Science B.V. All rights reserved.
  • K Yagi, C Oyanagi, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 118 4 1653 - 1660 2003年01月 [査読有り][通常論文]
     
    A highly accurate potential energy function for H2CO has been developed at the CCSD(T)/cc-pVTZ level. The potential energy function is generated by the modified Shepard interpolation of the local fourth-order Taylor expansions defined at three reference points, i.e., the equilibrium structure plus two symmetrically equivalent structures located in the strongly coupled region of CH symmetric (Q(1)) and antisymmetric (Q(5)) stretching vibrational coordinates. The vibrational self-consistent field and the following vibrational configuration interaction methods have been applied to determine the fundamentals, overtones, and combination bands of H2CO. It is shown that our proposed potential energy function and a conventional quartic force field provide the different result related to the assignment of the 1(1)5(1) and 1(1)3(1)6(1) bands. The calculated vibrational energies are in good agreement with the corresponding experimental values, showing the mean absolute deviation of 7.7 cm(-1). (C) 2003 American Institute of Physics.
  • T Taketsugu, DJ Wales
    MOLECULAR PHYSICS 100 17 2793 - 2806 2002年09月 [査読有り][通常論文]
     
    The global minimum and transition states for the acceptor-tunnelling, donor-acceptor interchange and bifurcation tunnelling rearrangements of the water dimer, and the single-flip, bifurcation and concerted proton transfer processes in the water trimer have been reinvestigated. Our analysis of the tunnelling splittings and spectroscopy is based on ab initio calculations at the computational level of second-order Moller-Plesset (MP2) theory with basis sets of aug-cc-pVXZ quality (X = D, T, Q for the dimer; X = D, T for the trimer). In both water dimer and trimer, the binding energy, barrier heights, intermonomer distances, and harmonic frequencies converge smoothly as the size of the basis set increases. In the water dimer, the binding energy was evaluated as 5.09 kcal mol(1), while the activation energies are 0.52 (acceptor-tunnelling) 0.79 (donor-acceptor interchange), and 1.94 kcal mol(1) (bifurcation tunnelling) at the MP2/aug-cc-pVQZ level. In the water trimer, the binding energy was evaluated as 16.29 kcal mol(1), while the activation energies are 0.28 (single-flip), 2.34 (bifurcation), and 26.36 (proton transfer) kcal mol(1) at the MP2/aug-cc-pVTZ level.
  • Y Kumeda, T Taketsugu, T Hirano
    CHEMICAL PHYSICS LETTERS 360 1-2 149 - 154 2002年07月 [査読有り][通常論文]
     
    Direct trajectory simulations have been carried out to investigate the growth mechanism of single-wall carbon nanotubes from the viewpoint of topological differences in the edge structure, i.e., zigzag or armchair, based on the semiempirical PM3 molecular orbital method. It is shown that the zigzag nanotube can grow smoothly if the zigzag is conserved form, while the armchair nanotube has a tendency to change into the chiral (or zigzag) form. These results agree with the static analysis of frontier electron density distributions in our recent reports as well as with the experimental observations of Sattler et al. (C) 2002 Elsevier Science B.V. All rights reserved.
  • K Yagi, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 116 10 3963 - 3966 2002年03月 [査読有り][通常論文]
     
    The potential energy function (PEF) for H2O has been generated by the modified Shepard interpolation method using the fourth-order Taylor expansion at the MP2/aug-cc-pVTZ level. The reference points for the interpolation have been set at only three points, i.e., the equilibrium structure plus two symmetrically equivalent points in the coupling region of OH symmetric and antisymmetric stretching modes. The vibrational self-consistent field (VSCF) and virtual configuration interaction (VCI) methods have been applied to determine fundamentals, overtones, and combination bands of H2O. The mean absolute deviation over these energy levels from the corresponding ones determined by the direct VCI method is only 4.8 cm(-1). (C) 2002 American Institute of Physics.
  • T Taketsugu, DJ Wales
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 4 10 1722 - 1724 2002年 [査読有り][通常論文]
     
    The potential energy surface of ClF4+ has been investigated using a multiconfiguration SCF reference second-order quasidegenerate perturbation theory (MC-QDPT) method with a cc-pVTZ basis set. It is shown that the D-4h structure corresponds to a transition state, which connects two permutational isomers of the C-4v structure, and the C-4v structure also corresponds to a transition state, which connects two permutational isomers of the C-2v global minimum, as for the Hartree-Fock surface characterised in previous work.
  • SS Itono, T Taketsugu, T Hirano, U Nagashima
    JOURNAL OF CHEMICAL PHYSICS 115 24 11213 - 11220 2001年12月 [査読有り][通常論文]
     
    Spectroscopic constants and energy levels of the ground (3)Delta (i) state (X (3)Delta (i)) and two low-lying excited states, (1)Delta and (5)Pi, of iron carbide FeC have been calculated by the ab initio multireference singles and doubles configuration interaction (MR-SDCI) molecular orbital method taking relativistic and spin-orbit coupling effects into account. Predicted rotational constant B-0 (0.6697 cm(-1)) and spin-orbit coupling constant A(SO) (-181 cm(-1)) for the X (3)Delta (2) state agree well with experimental values. The first (1)Delta state which is in isoconfiguration with the X (3)Delta state is predicted to lie at 3528 cm(-1) above the X (3)Delta (2) state with B-0, omega (e), and omega (e)x(e) values of 0.6861, 923, and 7 cm(-1), respectively. The lowest (5)Pi (2) state described by one electron excitation from nonbonding 1 delta orbital to antibonding 4 pi orbital should be located at 7248 cm(-1) above the X (3)Delta (2) state with B-0, omega (e), and omega (e)x(e) values of 0.6268, 850, and 5 cm(-1), respectively. Thus, considering the coincidence in the predicted excitation energy and spectroscopic constants for the (1)Delta state, the recently observed state at 3460 cm(-1) above the X (3)Delta (2) state by Aiuchi [Chem. Phys. Lett. 309, 229 (1999)], though tentatively assigned to the (5)Pi (2) state, should be reassigned to the (1)Delta state. (C) 2001 American Institute of Physics.
  • K Yagi, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 115 23 10647 - 10655 2001年12月 [査読有り][通常論文]
     
    The potential energy surface (PES) for the malonaldehyde intramolecular hydrogen atom transfer has been generated with full dimensionality by the modified Shepard interpolation method at the computational level of the second-order Moller-Plesset perturbation theory. The reference points have been set along the reaction path of H atom transfer (51 points), in a three-dimensional reaction space determined by geometrical features of the reaction path (219 points), and in the region of cis- and trans-enol isomerization reaction paths (428 points), so the resultant PES was generated in terms of ab initio data (energies, gradients, and Hessian matrices) of 698 reference points. Following trajectory simulations on the full-dimensional PES, the energy splitting of vibrational ground states due to tunneling was estimated by the semiclassical method of Makri and Miller [J. Chem. Phys. 91, 4026 (1989)]. The tunneling splitting was evaluated as 13.9 cm(-1), which is in good agreement with the experimental value of 21.6 cm(-1). (C) 2001 American Institute of Physics.
  • Tina Erica Odaka, Tetsuya Taketsugu, Tsuneo Hirano, Umpei Nagashima
    The Journal of Chemical Physics 115 3 1349 - 1354 2001年07月 [査読有り][通常論文]
     
    Spectroscopic constants of the first excited state of MgNC was found using three dimensional potential energy surfaces determined by molecular orbital calculations of Renner-Teller effect. Mg-NC bond length calculations predicted a linear equilibrium structure. Rotational and spin orbit coupling constants and Renner parameter were found to interpret laser induced fluorescence spectra.
  • Tetsuya Taketsugu, Stuart Carter
    Chemical Physics Letters 340 3-4 385 - 389 2001年06月 [査読有り][通常論文]
     
    The variational method is applied to determine the spin-rovibronic energy levels of MgNC in the A 2 Π electronic state. The calculations are based on the three-dimensional near-equilibrium potential energy surfaces of the 1 2 A″ and 2 2 A ′ states determined by the multireference singles and doubles configuration interaction method. Results are presented for energies up to 1000cm -1 , and compared with the corresponding values calculated by the perturbational method, as well as with gas-phase high resolution experimental results. © 2001 Elsevier Science B.V.
  • Y Nakao, K Hirao, T Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 114 18 7935 - 7940 2001年05月 [査読有り][通常論文]
     
    The equilibrium geometries, dissociation energies, and electronic structures of the ground and low-lying excited states for the first-row transition metal oxide cations, MO+ (M=Sc to Zn), have been studied using the multireference singles and doubles configuration interaction (MR-SDCI) and the multireference second-order Moller-Plesset methods. To investigate the applicability of the density functional theory (DFT) to an electronic structure system with a multiconfigurational character, the Becke exchange functional with the Lee-Yang-Parr correlation functional, the Becke exchange functional with the one-parameter progressive correlation functional (BOP), and the Becke three-parameter hybrid exchange functional with the Lee-Yang-Parr correlation functional (B3LYP) methods have also been applied. The DFT predicts the ground state M-O bond lengths in good agreement with the multireference-based methods except for MnO+ and CuO+, which have a multiconfigurational electronic structure. With respect to the dissociation energies, the B3LYP results are in good agreement with the multireference-based methods, while the DFT with pure functionals overestimates the energetics by about 20 kcal/mol compared to the MR-SDCI method. (C) 2001 American Institute of Physics.
  • T Taketsugu, Y Kumeda
    JOURNAL OF CHEMICAL PHYSICS 114 16 6973 - 6982 2001年04月 [査読有り][通常論文]
     
    The isotope effects on the bifurcating reaction path of the isomerization reaction, H3CO -->H2COH (stereoisomers of P and P*), have been investigated recently [J. Chem. Phys. 113, 477 (2000)], and it was found that the valley-ridge inflection point appears in the totally symmetric direction relative to the intrinsic reaction coordinate in the deuterium-substituted system. In the present report, the kinetic isotope effect on this reaction has been studied using an ab initio direct-trajectory method at the computational level of the complete active space self-consistent field method with 6-31G(d,p) basis sets. The branching ratio to the respective stereoisomers has been investigated in terms of distributions of several coordinates along the trajectories. The energy landscape for H3CO is also described in terms of several structures and the respective permutational isomers. (C) 2001 American Institute of Physics.
  • K Takeda, T Tsuchiya, H Nakano, T Taketsugu, K Hirao
    JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 537 107 - 115 2001年03月 [査読有り][招待有り]
     
    The kinetic and electronic stability of a series of free LnF(6)(q-)-type lanthanide hexafluorides (Ln = Ce to Lu; q = 2,3) is studied with the relativistic effective core potentials of Cundari and Stevens. In all complexes (LnF(6)(2-) and LnF(6)(3-)), the octahedral or almost octahedral structure is calculated to be stable through normal mode analyses at the unrestricted Hartree-Fock (UHF) and complete active space self-consistent field (CASSCF) levels. The electronic stability of all complexes is investigated using the state-averaged CASSCF and quasidegenerate perturbation theory with multiconfigurational self-consistent field reference functions (MC-QDPT) schemes. The most electronically stable LnF(6)(q-) is LnF(6)(2-) for Ce, Pr, Nd, Pm, Sm, Tb, Dy, Ho, Er, Tm, Yb. These LnF(6)(2-) anions are found to have an energy barrier with respect to the unimolecular decomposition LnF(6)(2-) --> LnF(6)(5-) + F- and are predicted to be long-lived species formally existing in a meta-stable state. (C) 2001 Elsevier Science B.V. All rights reserved.
  • Y Nakao, K Hirao, T Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 114 12 5216 - 5223 2001年03月 [査読有り][通常論文]
     
    The reaction mechanism of Co(+) ((5)F,(3)F) with H(2)O has been studied by the ab initio multireference-based theory (MR-SDCI and MC-QDPT) and the density functional theory (B3LYP and BLYP). In the energetics derived by the MR-SDCI(+Q) plus the B3LYP zero-point vibrational energy, the ion-dipole complex, CoOH(2)(+), is initially formed with the binding energy of 38.2 (triplet) and 34.1 (quintet) kcal/mol, which is the most stable complex in the respective potential energy surfaces. Then, Co(+) activates one O-H bond of H(2)O, leading to the insertion complex, HCoOH(+). There are three possible dissociation channels from HCoOH(+), i.e., --> CoOH(+) + H, --> CoH(+) + OH, and --> CoO(+) + H(2). The third dissociation is expected to occur through the transition state of a four-centered structure, with the activation barrier of 61.6 (triplet) and 49.2 (quintet) kcal/mol, although this dissociation has not been detected in the experiment. The ground state of CoO(+) is predicted to be (5)Delta, and the lowest triplet state is (3)Gamma with the energy level of 20.8 kcal/mol above. The B3LYP provides the energetics qualitatively similar to the MR-SDCI(+Q) ones through the reactions, with the maximum deviation of 13 kcal/mol. The calculated results are consistent with experimental observations. (C) 2001 American Institute of Physics.
  • Y Kumeda, Y Fukuhiro, T Taketsugu, T Hirano
    CHEMICAL PHYSICS LETTERS 333 1-2 29 - 35 2001年01月 [査読有り][通常論文]
     
    For carbon nanotubes with open end, the relation between the distribution of frontier orbitals and the edge structure was studied by the Huckel and ab initio molecular orbital methods. When the edge of a nanotube takes a zigzag form, the frontier orbitals localize at the edge part irrespective of the tube length, and continuous growth can be expected according to the frontier electron theory; when the edge takes an armchair form, the frontier orbitals delocalize all over the tube surface, disfavoring the nanotube growth. These results coincide with the experimental observation by Sattler et al. (C) 2001 Elsevier Science B.V. All rights reserved.
  • Y Kumeda, T Taketsugu
    JOURNAL OF CHEMICAL PHYSICS 113 2 477 - 484 2000年07月 [査読有り][通常論文]
     
    The isotope effects on bifurcating reaction paths have been studied for two reactions, H3CO --> H2COH and HF+C2H4--> C2H5F, both of which have a valley-ridge inflection (VRI) point related to nontotally symmetric directions on the symmetry-conserved intrinsic reaction coordinate (IRC). As the result of the VRI occurrence, the IRC connects a reactant minimum, the transition state, and another first-order saddle point. The deuterium substitution of one or two hydrogen atoms in molecular systems reduces the symmetry of the IRC, resulting in the direct linkage of the transition state and a product minimum through the IRC. In the above two reactions with deuterium substitution, it is found that the VRI occurs relative to the totally symmetric directions. Analyses of the steepest descent paths that start from a zero-point energy region around the VRI point demonstrate that those paths bifurcate toward two different product minima. (C) 2000 American Institute of Physics. [S0021-9606(00)30126-X].
  • K Yagi, T Taketsugu, K Hirao, MS Gordon
    JOURNAL OF CHEMICAL PHYSICS 113 3 1005 - 1017 2000年07月 [査読有り][通常論文]
     
    The vibrational self-consistent field (VSCF) and virtual configuration interaction (VCI) methods are directly combined with ab initio electronic structure calculations for evaluations of the potential energy at VSCF quadrature points. Referred to as direct VSCF and direct VCI, respectively, these methods have been applied to evaluations of anharmonic vibrational energy levels of H2O and H2CO at the second-order Moller-Plesset MP2/aug-cc-pVTZ and MP2/cc-pVTZ computational levels, respectively. The purpose of the present study is to develop a direct methodology for vibrational state calculations by examining the accuracy of the results, as well as their computational costs. In addition, the accuracy and applicability of two approximate potential energy surfaces (PES), a quartic force field (QFF), and the PES determined by the modified-Shepard interpolation method (Int-PES), are investigated via comparisons of calculated energy levels of vibrational states with those derived by the direct methods. The results are analyzed in terms of three considerations: (i) truncations of higher-order intercoordinate couplings in the PES; (ii) mode-mode coupling effects; (iii) approximations in ab initio electronic structure methods. In the direct VCI calculations, the average absolute deviations in fundamental frequencies relative to the experimental values are 9.3 cm(-1)(H2O) and 34.7 cm(-1)(H2CO). The corresponding values evaluated with approximate PESs relative to those derived by the direct method are 35.0 cm(-1) (QFF) and 15.3 cm(-1) (Int-PES) for H2O, and 6.3 cm(-1) (QFF) and 10.3 cm(-1) (Int-PES) for H2CO. (C) 2000 American Institute of Physics. [S0021-9606(00)30427-5].
  • T Taketsugu, N Watanabe, K Hirao
    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT 138 135 - 136 2000年 [査読有り][招待有り]
     
    The ab initio potential energy surface was generated for the HSiOH cis-trans isomerization with three reaction paths, by the modified Shepard interpolation. The energy level shift due to tunneling was estimated by semiclassical trajectory simulations. A large tunneling effect was observed, which is in agreement with the experiments.
  • T Taketsugu, N Watanabe, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 111 8 3410 - 3419 1999年08月 [査読有り][通常論文]
     
    The ab initio potential energy surface (PES) for the HSiOH cis-trans isomerization was generated by the modified Shepard interpolation method at the computational level of the complete active space self-consistent field (CASSCF) method. This isomerization has three reaction paths, i.e., one in-plane and two out-of-plane paths, so the reaction-path PES (RP-PES) has first been generated by setting reference points on these paths for the interpolation. In this RP-PES, there is an artifact of potential ridges between the in-plane and out-of-plane paths. By adding molecular configurations around potential ridges as reference points, the global PES has been much improved (the potential ridges have disappeared). Following trajectory simulations on this full-dimensional PES, the energy level shift of vibrational ground states due to tunneling was estimated by the semiclassical method. It is verified that there is a relatively large tunneling effect in this reaction, which is consistent with the experimental observations. (C) 1999 American Institute of Physics. [S0021-9606(99)30332-9].
  • Y Nakao, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 110 22 10863 - 10873 1999年06月 [査読有り][通常論文]
     
    The reactions of the first-row transition metal cations, Sc(+) ((3)D, (1)D), Ni(+) ((2)D), Cu(+) ((1)S), with NH(3) have been studied by the multiconfigurational and multireference-based theories, to clarify the similarities and differences in the reactivity of early (Sc(+)) and late (Ni(+), Cu(+)) transition metal cations. In all the cases, the ion-dipole complex, MNH(3)(+), is initially formed with a C(3v) symmetry structure, which is the most stable complex in the respective potential energy surfaces except for Sc(+) ((1)D). The M(+)-NH(3) binding energy was evaluated as 42.4, 37.8, 50.9, and 48.1 kcal/mol for Sc(+) ((3)D), Sc(+) ((1)D), Ni(+), and Cu(+), respectively. In the second step, M(+) is expected to activate one N-H bond of NH(3), leading to the insertion complex, HMNH(2)(+). In Sc(+) ((3)D, (1)D), three different stationary points of HScNH(2)(+), i.e., C(s) (in-plane), C(s) (out-of-plane), and C(2v) structures, were located, which correspond to a minimum point, a first-order saddle point, and a second-order saddle point, respectively. In these complexes, the singlet state originating from Sc(+) ((1)D) is largely stabilized compared to the triplets. The singlet HScNH(2)(+) (in-plane) is calculated to be the most stable compound. There are three dissociation channels from HScNH(2)(+), i.e., -->ScNH(2)(+) + H, -->ScH(+) + NH(2), and -->ScNH(+) + H(2). The third dissociation occurs through the transition state of a four-centered structure, with a small activation barrier of 23 kcal/mol, in both singlet and triplet surfaces. As to the late transition metal cations Ni(+) and Cu(+), there is no intermediate complex of HMNH(2)(+), thus, all the dissociations occur through highly vibrational excitations of MNH(3)(+). The calculated results are consistent with experimental observations. (C) 1999 American Institute of Physics. [S0021-9606(99)31122-3].
  • T Tsuchiya, T Taketsugu, H Nakano, K Hirao
    JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 461 203 - 222 1999年04月 [査読有り][招待有り]
     
    Ab initio molecular orbital calculations are performed for a series of lanthanide trihalides LnX(3) (Ln = La to Lu; X = Cl, F), with the relativistic effective core potentials of Cundari and Stevens, to characterize the tendency in their electronic and geometric structures. In all the complexes (LnX(3)), the planar structure (D-3h symmetry) is calculated to be stable through normal mode analyses at the complete active space self-consistent field (CASSCF) levels. In the LnX(3), the number of 4f-electrons increases with increasing the atomic number, and 1.2-1.6 (2.1-2.2) electrons are transferred from Ln to Cl (F); the Ln-X bonds are dominated by charge-transfer but have a significant amount of covalent character that involves the Sd-orbital on Ln. It is also found that, along the lanthanide trihalide series, the first seven f-electrons occupy 4f-orbitals one by one from the lowest one up, while the second seven occupy 4f-orbitals from the highest one down, at the Hartree-Fock level. This occupation mechanism is explained in terms of the self-repulsion interactions between two electrons occupying the same spatial 4f-orbital. The Ln-X bond lengths, net charges, and vibrational frequencies show monotonic variation along the lanthanide series, which corresponds to the lanthanide contraction. State-averaged CASSCF calculations are also carried out for LnCl(3), in a combination with spin-orbit calculations using the atomic spin-orbit coupling constant for the f-electrons, to investigate the energy splitting of the nearly-degenerate low-lying states in the scheme of L-S coupling. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Y Kumeda, Y Minami, K Takano, T Taketsugu, T Hirano
    JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 458 3 285 - 291 1999年01月 [査読有り][通常論文]
     
    Dynamic reaction path (DRP) simulation of the HNC reversible arrow HCN isomerization reaction has been carried out at the HF/6-31G** level to search for an intramolecular vibrational energy redistribution (IVR) process converging to the reaction mode of vibration having an imaginary frequency near the transition state (TS). Starting at the TS, a molecule was pushed forward or backward with the least necessary excess energy in the direction of the reaction mode. The thus started DRP, proposed here as intrinsic dynamic reaction path (IDRP), was analyzed in terms of vibration mixing and vibration mapping methods, giving an example of the IVR process to build up the reaction mode from randomly distributed vibration modes. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Y Akinaga, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 109 24 11010 - 11017 1998年12月 [査読有り][通常論文]
     
    Photofragmentations of a methane molecule adsorbed on Pd and Ni(111) surfaces have been studied by means of density functional theory (DFT) and ab initio molecular orbital calculations. The metal surfaces were represented approximately by finite metal clusters M-n (n = 1, 7, 10). The CH4-3s Rydberg excited state is found to be stabilized by about 2.0 and 1.5 eV through the physisorption on Pd and Ni metal surfaces, respectively. This stabilization can be understood as the results of the electron transfer from adsorbates to metal surfaces through an overlap between the CH4 Rydberg orbital and the metal s orbital. Potential energies of the ground and several excited states for the H3C ... HMn system as functions of the C ... H distance suggest that the charge transfer states lead to the fragmentation of CH4 to CH3 and H. The CH4 photodissociation for Pd and Ni(111) surfaces occurs through a direct excitation and the mechanism is basically the same as what we found for the CH4/Pt(111) system [J. Chem. Phys. 107, 415 (1997)]. (C) 1998 American Institute of Physics. [S0021-9606(98)31148-4].
  • Tetsuya Taketsugu, Takeshi Yanai, Kimihiko Hirao, Mark S. Gordon
    Journal of Molecular Structure: THEOCHEM 451 1-2 163 - 177 1998年09月 [査読有り][招待有り]
     
    Dynamical processes involving the reaction SiH 4 + F - → SiH 4 F - and the relation between the incident path of F - and SiH 4 F - pseudorotation are studied by employing a dynamic reaction path (DRP) method. The DRPs are analyzed in terms of a function which estimates the distance between any geometry and a reference geometry in configuration space. SiH 4 F - has only one trigonal bipyramidal minimum, with F axial, and two different transition states (first-order saddle points): a trigonal bipyramid with F equatorial (TS 2 ) and a square pyramid with F apical (TS 1 ). This gives rise to a valley-ridge inflection point on the reaction path between TS 1 and TS 2 . To investigate dynamical effects of the valley-ridge inflection on the behavior of SiH 4 F - , several directions of attack have been considered. The DRP analyses illustrate that, in contrast to SiH - 5 , it is difficult to induce pseudorotations in SiH 4 F - ; instead, scattering of F - is observed in most cases. Only for side attacks in which C 2ν symmetry is preserved does pseudorotation between two equivalent TS 2 structures occur. If the initial position of F - deviates even very slightly from this C 2ν path, the F - collides just once with SiH 4 , essentially along the C 2 axis. Then, due to the valley-ridge inflection, the system rapidly loses C 2ν symmetry, entering the C s subspace. In this case, several pseudorotations occur between two equivalent axial minima. The S N 2 reaction, SiH 4 + F - → SiH 3 F + H - , was not observed, but the abstraction reaction, F - + SiH 4 → HF + SiH - 3 , does occur for a back attack. © 1998 Elsevier Science B.V. All rights reserved.
  • Takeyuki Takata, Tetsuya Taketsugu, Kimihiko Hirao, Mark S. Gordon
    The Journal of Chemical Physics 109 11 4281 - 4289 1998年09月 [査読有り][通常論文]
     
    An ab initio potential energy surface for the six-atom reaction CH 3 +H 2 →CH 4 +H was constructed, within C 3v symmetry, by a modified Shepard interpolation method proposed recently by Collins et al. Selection of data points for the description of the potential energy surface was performed using both the Collins method and the dynamic reaction path (DRP) method. Although the DRP method is computationally more expensive, additional data points can be determined by just one simulation. Analyses of distributions of the data points, reaction probability, and errors in energy and energy gradients determined by the two different methods suggest a slight advantage for the DRP sampling in comparison with the iterative sampling. © 1998 American Institute of Physics.
  • T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 107 24 10506 - 10514 1997年12月 [査読有り][通常論文]
     
    We propose a least-action variational method to determine the optimal tunneling paths in multidimensional polyatomic reactions on the basis of the minimum energy path (MEP) and the least motion path (LMP). Taking into account geometrical features of the MEP (i.e., variations of path tangent and path curvature or variations of reaction plane along the MEP), the tunneling path is determined to minimize the amount of exponential damping of the nuclear wave function in the passage through the classically forbidden region. As a demonstration, the method is applied to a polyatomic reaction, NH3+OH-->NH2+H2O, in which there are highly curved regions on the MEP before and after a transition state. It is shown that the imaginary action integral calculated along the variationally determined tunneling path decreases extensively in comparison with that calculated along the MEP. (C) 1997 American Institute of Physics.
  • T Yanai, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 107 4 1137 - 1146 1997年07月 [査読有り][通常論文]
     
    Theoretical study has been given on bifurcating reaction paths where the intrinsic reaction path (IRP) has a valley-ridge inflection (VRI) point on the way from transition state to product, and leads to another first-order saddle point which connects two symmetrically equivalent products. To extract dynamically important regions in the configuration space between the VRI point and products, a group of steepest descent paths are calculated starting from zero-point energy regions at the VRI point, and the obtained configuration space is analyzed in terms of the reaction coordinate and the normal coordinate. The method is applied to Berry pseudorotations in SiH4F- and PH4F, H3CO-->H2COH, and cyclopropylidene-->allene, by employing the second-order Moller-Plesset and complete active space self-consistent field ab initio molecular orbital calculations. It is shown that the extension of bifurcating reaction paths largely depends on the position of the VRI point on the IRP. For the respective reactions, non-totally symmetric excited states are calculated along the IRP to understand the valley-ridge inflection mechanism in terms of the second-order Jahn-Teller effect. The isotope effect on bifurcating reaction paths is also investigated. (C) 1997 American Institute of Physics.
  • Y Akinaga, T Taketsugu, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 107 2 415 - 424 1997年07月 [査読有り][通常論文]
     
    The photodissociation of CH4/Pt(lll) is studied by density functional theory and the state-averaged complete active space self-consistent field (SA-CASSCF) method using a cluster model Pt-n (n = 1,4,6,7,10). With the small clusters (n less than or equal to 4), the equilibrium molecule-surface distances (H3CH-Pt) are less than 2.3 Angstrom and the binding energies are 4-14 kcal/mol, the order of the chemisorption. With larger clusters, the molecule-surface distance and the binding energy are calculated to be 3.00 Angstrom and 0.67 kcal/mol, respectively, of the order of the physisorption, which coincides with the experiments. The SA-CASSCF calculations verify that, in spite of the weak interaction between CH4 and Pt-n in the ground state, the first excited state of CH4 (Rydberg type) interacts with Pt-n unoccupied states strongly, resulting in the charge-transfer state and finally leading to the dissociation to CH3+H(-Pt); on the Pt(lll) surface, the excitation energy to the Rydberg state of CH4 decreases by similar to 3 eV compared to that in an isolated CH4 molecule. These results support the experimental results that the direct excitation of CH4 is invoked on the Pt(lll) surface by irradiation of the 193 nm photon, leading to the dissociation to CH3 and H. (C) 1997 American Institute of Physics.
  • N Tajima, T Taketsugu, K Hirao
    CHEMICAL PHYSICS 218 3 257 - 265 1997年06月 [査読有り][通常論文]
     
    The mechanism of water adsorptions onto the H-form zeolite, as well as the following proton exchange reaction, has been studied by ab initio molecular orbital calculations at the Hartree-Fock and the 2nd-order Moller Plesset levels with basis sets of double-zeta plus polarization quality. The H-form zeolite is represented by clusters consisting of 3 similar to 8 SiO4(AlO4) units. Some adsorption structures are located, and the normal mode analyses are performed for the respective structures to verify their geometric character and to determine the vibrational frequencies. The adsorption energies indicate that two types of complexes, i.e., a protonated form and a H-bonded form, are evenly probable as surface species, whenas the comparison of the calculated harmonic frequencies with the experimentally observed ones suggests that the adsorbed water forms the H-bonded complex. The potential energy surface related to the water adsorption and proton exchange processes is extensively investigated in terms of energy profiles along some energetically optimum paths.
  • T Taketsugu, MS Gordon
    JOURNAL OF CHEMICAL PHYSICS 106 20 8504 - 8515 1997年05月 [査読有り][通常論文]
     
    To investigate the mechanism for N-H bond activation by a transition metal, the reactions of Co+(F-3,F-5) With NH3 have been studied with complete active space self-consistent field (CASSCF), multireference configuration interaction (MR-SDCI), and multireference many body perturbation theory (MRMP) wave functions, using both effective core potential and all-electron methods. Upon their initial approach, the reactants yield an ion-molecule complex, CoNH3+(E-3,(5)A(2),(5)A(1)), With retention of C-3v symmetry. The Co+=NH3 binding energies are estimated to be 49 (triplet) and 45 (quintet) kcal/mol. Subsequently, the N-H bond is activated, leading to an intermediate complex H-Co-NH2+ (C-2v symmetry), through a three-center transition state with an energy barrier of 56-60 (triplet) and 70-73 (quintet) kcal/mol. The energy of H-Co-NH2+, relative to that of CoNH3+, is estimated to be 60 to 61 (triplet) and 44 (quintet) kcal/mol. However, the highest levels of theory employed here (including dynamic correlation corrections) suggest that the triplet intermediate HCoNH2+ may not exist as a minimum on the potential energy surface. Following Co-N or H-Co bond cleavage, the complex H-Co-NH2+ leads to HCo++NH2 or H+CoNH2+. Both channels (triplet and quintet) are found to be endothermic by 54-64 kcal/mol. (C) 1997 American Institute of Physics.
  • T Taketsugu, N Tajima, K Hirao
    JOURNAL OF CHEMICAL PHYSICS 105 5 1933 - 1939 1996年08月 [査読有り][通常論文]
     
    The intrinsic reaction path (IRP) often becomes unstable relative to some nontotally symmetric direction orthogonal to the path through a valley-ridge inflection point. We investigate geometric characters of the potential energy surface around the valley-ridge inflection boundary, and propose some ideas to determine a bifurcating reaction path, or to give a two-dimensional potential energy surface which connects bifurcating point and product regions. As a demonstration, bifurcating reaction paths are calculated for the isomerization reaction of methoxy radical (H3CO-->H2COH) by the unrestricted Hartne-Fock (UHF) method. (C) 1996 American Institute of Physics.
  • Mark S. Gordon, Galina Chaban, Tetsuya Taketsugu
    The Journal of Physical Chemistry 100 11512 - 11525 1996年06月 [査読有り][通常論文]
     
    This paper illustrates the utility of combining high-quality electronic structure calculations, methods for determining reaction paths, and direct dynamics methods for studying ab initio trajectories on the fly to develop an understanding of complex chemical reactions. The combined methods are applied to the pseudorotation in SiH 5 - competing dissociation paths for N 2 O 2 the dissociation of FN 3 into NF + N 2 and the potential energy surfaces for AlH 2 . These DRP results may be thought of as samples of what dynamical processes can be encountered on each potential energy surface.
  • T Taketsugu, T Hirano
    JOURNAL OF CHEMICAL PHYSICS 104 16 6081 - 6088 1996年04月 [査読有り][通常論文]
     
    A perturbational method in terms of cubic force constants was proposed to predict how intramolecular vibration mixing among normal modes occurs through the anharmonicity of the potential energy. The method was applied to H2O and it was predicted that symmetric and antisymmetric stretching normal modes having similar frequencies should couple strongly with each other, even at the equilibrium point moiety, as the antisymmetric normal vibration develops. Dynamic reaction path calculations were also performed for H2O, and the strong vibration coupling between those predicted normal vibration pair was confirmed. (C) 1996 American Institute of Physics.
  • T Taketsugu, MS Gordon
    JOURNAL OF CHEMICAL PHYSICS 104 8 2834 - 2840 1996年02月 [査読有り][通常論文]
     
    We propose a reaction path-based Hamiltonian in terms of the reaction coordinate, the curvature coordinate, the remaining 3N-8 transverse normal coordinates (whose directions are orthogonal to the path tangent and curvature vectors), and their conjugate momenta, for an N atomic reaction system. The 3N-8 transverse vibrational modes are independent of the motion along the reaction path, although they have coupling terms with the curvature direction in the harmonic approximation. A two-dimensional plane determined by the path tangent and curvature vectors is termed the ''reaction plane.'' We introduce a function that estimates changes of the reaction plane along the reaction path, and analyze the reaction path based on this function for an abstraction reaction, CH3+H-2-->CH4+H. The scheme proposed here should be effective when a reaction path has a sharply curved region. (C) 1996 American Institute of Physics.
  • T TAKETSUGU, MS GORDON
    JOURNAL OF CHEMICAL PHYSICS 103 23 10042 - 10049 1995年12月 [査読有り][通常論文]
     
    We propose two methods that may be used to describe the dynamic reaction path (DRP) based on an intrinsic reaction coordinate (IRC) or minimum energy path, to examine how the actual dynamics proceeds relative to the IRC path. In the first of these, any point on the DRP is expressed in terms of the IRC and the distance from the LRC path. In the second method, any DRP point is expressed in terms of the IRC, the curvature coordinate, and the distance from a two-dimensional ''reaction plane'' determined by the IRC path tangent and curvature vectors. The latter representation is based on the fact that the 3N-8 dimensional space orthogonal to the reaction plane is independent of an internal centrifugal force caused by the motion along the IRC path. To analyze the relation between geometrical features of the IRC path and the dynamics, we introduce a function that estimates the variation of the reaction plane along the IRC path. As demonstrations, the methods are applied to the dissociation reaction of thiofolmaldehyde (H2CS-->H-2+CS). (C) 1995 American Institute of Physics.
  • Tetsuya Taketsugu, Mark S. Gordon
    Journal of Physical Chemistry 99 14597 - 14604 1995年09月 [査読有り][通常論文]
     
    Recently, we proposed a dynamic reaction path (DRP) analysis with vibration mapping and examined symmetry-conserved processes in the reaction SiH 4 + H - → SiH 5 - (side and front attack). A key feature of this study was an analysis of the Berry pseudorotation mechanism in SiH 5 - from the viewpoint of vibration-vibration interactions. In the present study, we extend this methodology to deal with symmetry-relaxed attack by using a function that estimates the distance between any geometry and a reference geometry in configuration space, in order to examine the relation between the incident path of H - and the pseudorotation. When approaching SiH 4 from the side or back, the H - changes its path toward front attack, due to the high energy requirements for the side and back attack paths, resulting in a vibrationally active SiH 5 - with accompanying Berry pseudorotation. On the other hand, in a frontal or nearly frontal attack, SiH 5 - seems stable with no pseudorotation. © 1995 American Chemical Society.
  • Tetsuya Taketsugu, Mark S. Gordon
    Journal of Physical Chemistry 99 21 8462 - 8471 1995年05月 [査読有り][通常論文]
     
    An ab initio classical trajectory method, the dynamic reaction coordinate (DRC) method based on ab initio electronic structure calculations, is applied to a study of the chemical reaction SiH 4 + H - → SiH 5 - . Both side attack (C 2v , symmetry) and front attack (C 3v . symmetry) of H - on SiH 4 are examined. To analyze the nature of the intramolecular vibrational energy transfer, the DRC and its corresponding momentum are mapped onto normal modes of both reactant and product systems. These analyses show that Berry pseudorotation occurs repeatedly in the SiH 5 - produced by the side attack, whereas the S N 2 reaction H - + SiH 4 → SiH 4 + H - often occurs upon front attack depending on the initial relative velocity. © 1995 American Chemical Society.
  • K NASU, T TAKETSUGU, T NAKANO, U NAGASHIMA, H HOSOYA
    THEORETICA CHIMICA ACTA 90 2-3 75 - 86 1995年01月 [査読有り][通常論文]
     
    By semi-empirical molecular orbital calculations stability of fullerenes was analyzed in terms of topological parameters, such as the number of special fragments and the number of three types of abutting bonds between two 5-membered rings. Relative stability was compared by AM1 method for all spectrally distinct closed-shell isomers of C-36 and C-40 fullerenes, and for some closed-shelf isomers of C-60 fullerene. Molecular geometries of these fullerenes were also optimized. Their relative stabilities were well explained by the instability of abutting bonds.
  • T TAKETSUGU, T HIRANO
    JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 115 1 37 - 44 1994年05月 [査読有り][通常論文]
     
    The vibrational state transition of a polyatomic molecule due to a uniform electric field (EF) has been studied. Depending on the changing rate of the applied EF, either sudden or adiabatic approximation can be applied for the state transition; the former leads to a vibrational excitation and the latter to a distortion of molecular geometry without excitation. The case of the H2O molecule in a uniform EF is demonstrated by the second-order Moller-Plesset method based on the unrestricted Hartree-Fock scheme with 6-31G** basis sets. A new concept, ''equi-quantum number map'', has been presented to analyze the transition of the vibrational state due to the EF.
  • T NAKANO, T TAKETSUGU, T HIRANO
    JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM 111 111 - 115 1994年03月 [査読有り][通常論文]
     
    A new type of transition state showing ''cusp'' in the energy profile due to the interchange of the roles of SOMO and second-HOMO was encountered in the simulation of the photo-assisted organometailic vapor phase epitaxy process. This cusp feature does not disappear even in the two-configuration SCF (TCSCF) energy profile. A Brillouin-type theorem for an open-shell system with a SOMO has been derived for the explanation.
  • Tetsuya Taketsugu, Tsuneo Hirano
    Journal of Molecular Structure: THEOCHEM 310 169 - 176 1994年 [査読有り][招待有り]
     
    It is known that the reaction path for the dissociation reaction H2CS → H2 + CS has Cs symmetry while the reaction path for the isomerization reaction H2CS → HCSH has C1 symmetry at the Hartree—Fock (HF) level. In addition, the former reaction path is known to have a bifurcating region. In order to clarify the bifurcation mechanism in terms of the second-order Jahn—Teller (SOJT) effect, the intrinsic reaction coordinates (IRCs) and energies of the first-excited state (A″) along the IRC were calculated for both reactions under the constraint of Cs symmetry with 6–31G** basis sets at the HF level and at the complete active space SCF (CASSCF) level. At the HF level, bifurcation was proven to occur in both dissociation and isomerization reactions due to a vibronic interaction through the SOJT effect. At the CASSCF level, however, the energy separations between the ground and the A″ excited states in both reactions are large enough to avoid state intermixing due to the SOJT effect, and the bifurcation disappears from each IRC. For the purpose of comparison, the IRCs of H2CO for the dissociation to H2 + CO and for the isomerization to HCOH were also calculated with 6–31G** basis sets at the HF level. As expected from the SOJT theory for the calculated large energy separation, bifurcation does not occur in both dissociation and isomerization reactions of H2CO. © 1994, Elsevier Science B.V. All rights reserved. All rights reserved.
  • Tsuneo Hirano, Tetsuya Taketsugu, Yasuyuki Kurita
    Journal of Physical Chemistry 98 28 6942 - 6949 1994年 [査読有り][通常論文]
     
    Vibration mixing and vibration mapping, which we proposed recently as novel methods to describe vibrational interaction in terms of normal modes, were applied for the prediction and understanding of the transition normal vibration (TNV) in atom + molecule type reactions (H• + H-H → , H• + H2C=CH2 → , and H- + oxirane → ). According to the equations of vibration mixing, we derived vibration mixing rules for the prediction of the TNV which consist of a principle for the selection of the candidate normal modes growing into the TNV and of the estimation of the sign and magnitude of the mixing coefficients for the normal modes to mix in. Thus, the possible TNVs can be predicted by pictorial examination of the normal modes of the reactants. The results are in good agreement with those of vibration mapping. © 1994 American Chemical Society.
  • Tsuneo Hirano, Tetsuya Taketsugu, Yasuyuki Kurita
    Journal of Physical Chemistry 98 28 6936 - 6941 1994年 [査読有り][通常論文]
     
    For the understanding and prediction of molecular properties and chemical reactions in terms of vibration interaction, two methods, i.e., vibration mixing and vibration mapping, are proposed. Equations for vibration mixing, derived by a perturbational method, can predict qualitatively how the normal modes of fragment molecules mix with each other in the interacting system. Vibration mapping can show quantitatively how the vibration mixing in the interacting system occurs. For demonstrations, these two methods were applied to the HF-NH3 and H2CO-H2O systems. © 1994 American Chemical Society.
  • T TAKETSUGU, T HIRANO
    JOURNAL OF CHEMICAL PHYSICS 99 12 9806 - 9814 1993年12月 [査読有り][通常論文]
     
    The mechanism of bifurcation along the reaction path on an adiabatic potential surface is discussed in terms of the second-order Jahn-Teller (SOJT) effect. From the viewpoint of this SOJT effect, bifurcation occurs due to the mixing of the nearest nontotally symmetric electronic excited state into the electronic ground state through a molecular vibration belonging to the same nontotal symmetry. Thus, the bifurcating region should be limited where the excited state comes close to the ground state. In order to demonstrate our SOJT theory of bifurcation, we calculated intrinsic reaction coordinates (IRC) of thioformaldehyde under C(s) symmetry constraint for the dissociation reaction to H-2+CS and for the isomerization reaction to thiohydroxycarbene (HCSH). Energies of the lowest excited electronic state (A'') were also calculated along the IRC. These calculations were performed with 6-31G** basis sets at three different computational levels: (1) HF level, (II) SDCI level for HF geometries, and (III) full valence complete active space self-consistent field (CASSCF) level. As is expected from our theory, bifurcations observed for both dissociation and isomerization reactions at the HF level disappear at the CASSCF level due to the larger energy separation between ground and excited states. For the isomerization reaction, while the previous calculations at the HF level predicted that the transition state and IRC should have C1 symmetry, the transition state and IRC are proved to have C(s) symmetry at the CASSCF level as the result of the disappearance of bifurcation.

書籍

  • 新しい化学教育研究会 (担当:共著範囲:第3章 化学結合と分子構造)
    学術図書出版社 2019年04月 (ISBN: 9784780607635) iv, 333p
  • Frontiers of Quantum Chemistry
    Tetsuya Taketsugu, Yu Harabuchi (担当:分担執筆範囲:Ab initio molecular dynamics study on photoisomerization reactions: Applications to azobenzene and stilbene)
    Springer 2017年 pp431-453
  • 新版 すぐできる 量子化学計算ビギナーズマニュアル (KS化学専門書)
    武次徹也, 平尾公彦 (担当:編者(編著者))
    講談社サイエンティフィク 2015年03月 (ISBN: 4061543881) 224
  • π-Stacked Polymers and Molecules: Theory, Synthesis, and Properties
    Takao Tsuneda, Tetsuya Taketsugu (担当:分担執筆範囲:π-Stacking on Density Functional Theory: A review)
    Springer 2013年 pp 245-270
  • Advances in Quantum Monte Carlo
    Akira Nakayama, Tetsuya Taketsugu (担当:分担執筆範囲:Chapter 3. Enhancement of sampling efficiency in ab initio Monte Carlo simulations using an auxiliary potential energy surface)
    ACS symposium series vol 1094 2012年 pp 27-40
  • Hydrogen Bonding and Transfer in the Excited State
    Tetsuya Taketsugu, Daisuke Kina, Akira Nakayama, Takeshi Noro, Mark S. Gordon (担当:分担執筆範囲:QM/MM Study of Excited State Solvation Dynamics of Biomolecules)
    Wiley 2010年 pp. 579-588
  • 武次 徹也, 平尾 公彦, 武次 徹也, 平尾 公彦 (担当:編者(編著者))
    講談社サイエンティフィク 2006年04月 (ISBN: 406154330X) 236
  • 武次 徹也, 平尾 公彦 (担当:共著)
    裳華房 2003年01月 (ISBN: 4785334096) 114
  • The Transition State: A Theoretical Approach
    Tetsuya Taketsugu, Kimihiko Hirao (担当:分担執筆範囲:3. Molecular Symmetry and Transition State)
    Kodansha-Gordon and Breach Science Publishers 1999年 pp45-63
  • Theory of Chemical Reaction in terms of Normal Modes of Vibration
    武次徹也 (担当:単著)
    学位論文(東京大学) 1994年03月
  • 分子軌道法MOPACガイドブック”第2版
    武次 徹也 (担当:分担執筆範囲:10章.遷移状態の計算法とキーワード SADDLE,NLLSQ,TS 等の使用法)
    海文堂 1994年 pp187-203

講演・口頭発表等

  • Theoretical suggestion and experimental proof for functionalization of h-BN by gold as electrocatalysts for ORR and HER  [招待講演]
    Tetsuya Taketsugu, Andrey Lyalin, Min Gao, Kohei Uosaki
    256th ACS National Meeting "Fundamental Understanding of Catalysis at Interface through Computational Approach" 2018年08月 口頭発表(招待・特別) Boston
  • Reaction Path Concept in Quantum Chemistry and Dynamics Effects  [招待講演]
    TAKETSUGU Tetsuya
    Geometry of Chemical Reaction Dynamics in Gas and Condensed Phases, TSRC workshop 2018年07月 口頭発表(招待・特別) Telluride
  • Dynamic Reaction Routes beyond the IRC network  [招待講演]
    TAKETSUGU Tetsuya
    7th JCS SYMPOSIUM (Quantum chemistry, from methodology to applications in organic, inorganic, biochemistry and material sciences) 2018年05月 口頭発表(招待・特別) PRAGUE
  • 理論と実験のインタープレイから生まれた新しい触媒:BN/Au  [招待講演]
    武次徹也, Andrey Lyalin, Min Gao, 魚崎浩平
    ワークショップ「理論と実験の融合による高難度物質変換の反応機構解明にむけて」 2018年05月 口頭発表(招待・特別) 札幌
  • 固有反応座標と動力学効果  [招待講演]
    武次徹也
    ワークショップ 「複合系の理論化学・計算化学:最近の研究状況と展望」 2018年04月 口頭発表(招待・特別) 京都
  • Theoretical study of reactivity of gold clusters: Structural effects and support effects  [招待講演]
    Tetsuya Taketsugu
    APS March Meeting "Nano and sub-nano clusters as the smallest and highly-tunable interfaces" 2018年03月 口頭発表(招待・特別) Los Angels
  • 理論計算による未知触媒開発と未知反応機構解明  [招待講演]
    武次徹也
    計算材料学センター セミナーシリーズ スパコンプロフェッショナル No.11 2018年02月 口頭発表(招待・特別) 仙台
  • 量子化学研究の最新の展開:振動状態理論・反応経路網・ダイナミクス  [招待講演]
    武次徹也
    2017 年度「物質階層原理研究」研究報告会 2018年02月 口頭発表(招待・特別) 和光
  • Theoretically inspired new catalyst: boron nitride with gold  [招待講演]
    TAKETSUGU Tetsuya
    2018 Mesilla Chemistry Workshop on Interplay between Theory and Experiment in Nanocatalysis 2018年02月 口頭発表(招待・特別) Mesilla
  • 元素戦略にもとづく触媒開発研究 ~理論計算と実験実証のインタープレイ~  [招待講演]
    武次徹也
    スーパーコンピュータワークショップ2017「機能性材料設計への最新の計算科学アプローチ」 2018年01月 口頭発表(招待・特別) 東岡崎
  • 隠れた反応経路 - 固有反応座標を超えて  [招待講演]
    武次徹也
    化学科主催研究会「お茶の水女子大学の理論化学と計算化学」 2017年12月 口頭発表(招待・特別) 茗荷谷
  • 解離性再結合反応の 第一原理分子動力学シミュレーション  [招待講演]
    武次徹也
    宇宙生命計算科学連携拠点第 3 回ワークショップ 2017年11月 口頭発表(招待・特別) 筑波
  • 北大理論化学グループの元素戦略プロジェクト:これまでの成果と今後の計画  [招待講演]
    武次徹也, 岩佐豪, 高敏, 小林正人, 前田理, 中山哲, Andrey Lyalin, Raman Singh
    ESICB電子論 second kick-off会議 2017年11月 口頭発表(招待・特別) 京都
  • Theoretical Suggestion and Experimental Proof for Novel Catalyst: Boron Nitride with Gold  [招待講演]
    TAKETSUGU Tetsuya
    The 2017 International Conference on Functional Carbons (ICFC) 2017年11月 口頭発表(招待・特別) Taipei
  • Reaction-path bifurcation analyses based on Valley-Ridge transition and global reaction route mapping  [通常講演]
    Tetsuya Taketsugu, Yu Harabuchi, Yuriko Ono, Takuro Tsutsumi, Satoshi Maeda
    The 11th Triennial Congress of the World Association of Theoretical and Computational Chemists (WATOC 2017) 2017年08月 口頭発表(一般) Munich
  • Computational approach to design of non-platinum catalyst for oxygen reduction reaction: boron nitride with gold  [招待講演]
    Tetsuya Taketsugu, Andrey Lyalin, Min Gao, Kohei Uosaki
    The 21st International Annual Symposium on Computational Science and Engineering (ANSCSE21) 2017年08月 口頭発表(招待・特別) Pathum Thani, Thailand
  • A Hidden Feature in Static Intrinsic Reaction Coordinate Analysis: Bifurcation  [招待講演]
    TAKETSUGU Tetsuya
    3rd Japan-Thai workshop on Theoretical and Computational Chemistry 2017 2017年07月 口頭発表(招待・特別) Yokohama
  • Theoretical approach to reaction-path bifurcation  [招待講演]
    TAKETSUGU Tetsuya
    INTERNATIONAL SYMPOSIUM ON PURE & APPLIED CHEMISTRY (ISPAC) 2017 2017年06月 口頭発表(招待・特別) Ho Chi Minh, Vietnam
  • AIMD study on pipi*-excited substituted-stilbene  [通常講演]
    Tetsuya Taketsugu, Rina Yamamoto, Takuro Tsutsumi, Yu Harabuchi, Satoshi Maeda
    57th Sanibel Symposium 2017年02月 ポスター発表 St. Simons Island
  • Ab initio MD study of branching reactions in the excited-state potential energy surface  [招待講演]
    武次 徹也
    GAMESS7557 Meeting 2017年01月 口頭発表(招待・特別) Kauai
  • 反応経路自動探索法の金属クラスター触媒への応用と表面触媒反応への展開  [招待講演]
    武次徹也, 前田 理, 岩佐 豪, 小林正人, 高 敏, 中山 哲, Andrey Lyalin
    ESICB触媒検討会 2017年01月 口頭発表(招待・特別) 京都
  • 理論計算が拓く非白金燃料電池触媒探索の試み  [招待講演]
    武次徹也
    ポスト「京」重点課題5 「エネルギーの高効率な創出,変換・貯蔵,利用の新規基盤技術の開発」第3回公開シンポジウム 2016年12月 口頭発表(招待・特別) 東京
  • 触媒開発に理論化学は役に立つか? 未知触媒と未知反応機構へのアプローチ  [招待講演]
    武次徹也
    住友化学講演会 2016年12月 公開講演,セミナー,チュートリアル,講習,講義等 千葉
  • Ab Initio Approach to Photoreaction Dynamics  [招待講演]
    TAKETSUGU Tetsuya
    Thai-Japan Symposium in Chemistry 2016年11月 口頭発表(招待・特別) Chiang Mai
  • On-the-fly dynamics study on the photoisomerization mechanism of stilbene and its derivative  [招待講演]
    TAKETSUGU Tetsuya
    Japan-France-Spain Joint-Symposium on Theoretical and Computational Science of Complex Systems 2016年10月 口頭発表(招待・特別) Kyoto
  • Theoretical study of substituent effects on excited-state dynamics of stilbene  [招待講演]
    TAKETSUGU Tetsuya
    2nd Japan-Thai workshop on Theoretical and Computational Chemistry 2016 2016年09月 口頭発表(招待・特別) Yokohama
  • 反応経路分岐の理論化学  [招待講演]
    武次徹也
    有機反応機構研究会 2016年09月 口頭発表(招待・特別) 長崎
  • Ab initio study of photo-isomerization reaction dynamics  [招待講演]
    TAKETSUGU Tetsuya
    INTERNATIONAL SYMPOSIUM ON PURE & APPLIED CHEMISTRY (ISPAC) 2016 2016年08月 口頭発表(招待・特別) Kuching, Malaysia

その他活動・業績

受賞

  • 2019年03月 日本化学会 学術賞
     第一原理計算に基づく電子励起状態反応素過程とダイナミクスの解明 
    受賞者: 武次 徹也

共同研究・競争的資金等の研究課題

  • 文部科学省:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2011年 -2012年 
    代表者 : 武次 徹也
     
    不安定分子種の分光定数を測定する手段として「希ガスマトリックス単離法」が広く利用されている。この手法では「希ガスの影響は無視できる」と仮定されているが、近年、対象分子種に対して希ガス原子が特異的に結合を形成する例がいくつか報告され、マトリックス単離法による分光データを見直す必要が生じている。希ガス化合物の高精度ab initio電子状態計算に基づく分光定数の決定は数多くなされているが、周囲のマトリックスの影響も考慮した計算報告例はほとんどない。たとえばBeOは希ガス原子と強く結合し、希ガス複合体RgBeOを形成することが報告されている。複合体形成によりBeOの伸縮振動スペクトルは大きくブルーシフトすることが量子化学計算により予測されているが、このシフト量はマトリックス中で観測されるシフト量に対してかなり大きい。本研究では、XeまたはArマトリックス中でのBeOの振動数について希ガス複合体形成と周囲のマトリックス環境が振動数に与える影響を定量的に議論するために、周囲の希ガス原子を古典的に扱った量子古典混合ハミルトニアンを定義し、モンテカルロシミュレーションを行った。BeOはBe側に一つの希ガス原子と特異的に強く結合するため、RgBeOの分子内振動を量子自由度とし、ポテンシャルはCCSD(T)法により求め、量子自由度を含む項については基準座標を用いたPO-DVR法によりマトリック...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2009年 -2011年 
    代表者 : 武次 徹也, 野呂 武司, 中山 哲
     
    本課題では、動力学の手法に電子状態計算手法を融合させ、モデル系ではなく実在系の反応ダイナミクスをシミュレートする「第一原理反応動力学法」を確立することを目的として研究を進めている。本年度は、非断熱遷移を考慮したAIMD法を光異性化反応(スチルベン、アゾベンゼン)、光解離反応(CH3I)、DNA塩基(シトシン)の光安定性の検証へと適用し、反応機構、状態遷移機構を解明し、生成物の分岐比、励起寿命、エネルギー分布において実験値と良い一致を得ることに成功した。また、反応にそれほど関与しないと考えられる自由度を固定して分子動力学計算を行うRATTLE法をAIMDコードに実装し、タイムステップを長めにとることでコスト削減を実現した。さらにQM/MM法をAIMDコードに実装し、7-azaindole、Coumarinl51の溶液内励起緩和過程のダイナミクスへと適用し、緩和機構に関する知見を得た。また、生体分子で重要な役割を果たす励起プロトン移動で重要となるトンネル効果を議論する手法を構築するため、MakriとMillerが提案したWKB近似に基づく半古典法をAIMDコードに実装し、テスト計算として電子基底状態におけるマロンアルデヒドの分子内プロトン移動反応へと適用した。マロンアルデヒドの分子内プロトン移動反応におけるIRCは遷移状態前後で大きく曲がることが知られており、自由度間に過剰なエネ...
  • 文部科学省:科学研究費補助金(萌芽研究, 挑戦的萌芽研究)
    研究期間 : 2008年 -2009年 
    代表者 : 武次 徹也, 野呂 武司, 中山 哲
     
    本研究では、量子化学計算手法を凝縮系のダイナミクスに実装し、不安定分子種の分光定数を測定する手段として長らく利用されてきた「希ガスマトリックス単離法」を理論的にシミュレートする方法論を開発することを目的として研究を進めてきた。あわせて、希ガスマトリックス分光法で測定された実験データの中に希ガス化合物に帰すべきものが含まれていないか、高精度理論計算に基づき調べている。本年度は(1)キセノンとグラフェンの相互作用に関する高精度計算、(2)Ar-PtCO、Ar-PdCOの高精度分光定数予測、(3)希ガスマトリックス振動スペクトルシミュレーションプログラムの開発とキセノンマトリックス中に単離されたXe-BeOの振動スペクトルへの適用を行った。ここでは、すでに論文で報告を行った(2)について概要を述べる。モノカルボニル化合物PtCO,PdCOについてはArマトリックス中で測定された振動数が報告されているが、特に変角振動の振動数について、理論計算で得られる調和振動数と実験値との間に二倍ほどのずれがあった。他研究グループの論文では、何らかの理由で実験では倍音が測定されたのでは、と議論されていたが、その根拠についてはフェルミ共鳴の可能性が指摘されるのみで、解決には至っていなかった。本研究では、ArがPtCO,PdCOに10kcal/molのオーダーの結合エネルギーで付着し、変角モードの振動数...
  • 文部科学省:科学研究費補助金(特定領域研究)
    研究期間 : 2006年 -2009年 
    代表者 : 武次 徹也, 野呂 武司, 中山 哲
     
    多配置波動関数に基づく、電子励起状態に適用可能な非断熱遷移を実装したab initio分子動力学プログラムを完成させ、アゾベンゼンやスチルベンの光異性化反応、星間分子の解離性再結合反応、7アザインドールの励起プロトン移動、クマリン151の溶液内光反応へと適用して、反応分岐比、量子収率、反応経路、励起寿命の解明を行った。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2006年 -2008年 
    代表者 : 武次 徹也
     
    電子励起状態に適用可能な、Tullyの状態遷移アルゴリズムを実装したabinitio分子動力学プログラムを開発し、星間分子の解離性再結合反応HCNH+, H_3O^+, HD_2O^+, CH_3^+, (H_2O)_2H^+へと適用して、解離生成物の分岐比、動的反応経路、反応ダイナミクスの解明を行った。
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2002年 -2003年 
    代表者 : 武次 徹也
     
    水分子二量体・三量体において有効分子対称群を考えると、最安定構造に対する同種核置換異性体はそれぞれ8個、48個あり、各異性体をつなぐ反応経路は二量体で3種類(acceptor tunneling, acceptor-donor interchange, donor tunneling)、三量体で2種類(single flip, bifurcation tunneling)あることがわかっている。各水分子クラスターにおけるトンネル効果を理論の立場から定量的に調べるため、MP2, CCSD(T)/aug-cc-pVXZ(X=D,T)レベルの電子状態計算により最安定構造および各反応の遷移状態構造を求め、結合エネルギー、活性化エネルギーを比較したところ、MP2/aug-cc-pVTZレベルで十分精度良い結果が得られることがわかった。対象とする系が分子間力である水素結合を伴う系であることを考慮して、結合エネルギーおよび分子構造についてはcounterpoise法による基底関数重ね合せ誤差(BSSE)の補正をした計算も行ったが、電子相関を考慮した方法においてはBSSEの補正はむしろ行わない方が基底関数の大きさに関して良い収斂が得られることがわかった。次に、各異性体をつなぐ反応に対し、MP2レベルで決定した固有反応経路をトンネル経路と近似し、半古典論に基づいてトンネル相互作用項の大きさをそ...
  • 文部科学省:科学研究費補助金(特定領域研究(A))
    研究期間 : 2000年 -2001年 
    代表者 : 武次 徹也
     
    本申請課題では、内挿法によるab initioポテンシャル曲面(PES)生成法の一般化を行い、動力学の諸問題に応用することを目的とした研究を行った。まず、1994年にCollinsらによって提案された修正Shepard内挿法に基づくPESの生成法を、デカルト座標に基づいて定式化することにより一般の多原子分子系に適用できる形に拡張することに成功した。本方法を、(1)マロンアルデヒドの分子内水素移動反応・蟻酸二量体の分子間二重水素移動反応における多次元トンネル動力学、(2)水、ホルムアルデヒド分子の振動-回転エネルギー準位の予測、の2つの動力学の問題に応用した。以下順次成果を述べる:(1)反応経路が大きく曲がるためにトンネル効果を定量的に見積もることが困難な系として知られているマロンアルデヒドの分子内水素移動反応に対して全21自由度を含んだab initioポテンシャル曲面を作成し、Millerのモデルを適用してトンネル効果によるエネルギー分裂を評価したところ、実験値を非常に精度よく再現することができた。蟻酸二量体の分子間二重水素移動反応(24自由度)についても、同様にしてPESを作成し、simulationを行うことにより、トンネル分裂を定量的に見積もることができた。(2)振動-回転エネルギー準位を理論予測する振動SCF法にdirectに電子状態計算を組み合わせたdirect ...
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1998年 -1999年 
    代表者 : 武次 徹也
     
    本課題では多原子分子反応にも適用可能な半古典トンネルモデルの定式化を目的として研究を行った。初年度は、Truhlarらが2次元共線形に対して定式化した「最小作用原理に基づくトンネル経路モデル」の多次元系への一般化を試みた。彼らのモデルでは、経路に沿った虚の作用積分を最小にするために最小エネルギー経路(MEP)と最短移動経路(LMP)の重み付き平均として一群の経路を定義し、その重みを変分パラメーターとして作用積分の最小値を与える経路をトンネル経路とする。我々は、反応経路の接線・曲率ベクトルで決まる2次元の座標空間を局所的反応平面と定義してMEPに沿った変化を調べ、経路が大きく曲がる領域で反応平面は安定であること、MEP全体を反応平面のねじれに基づきいくつかの領域に分割できることを見い出した。この幾何学的性質を利用し、まず反応経路をねじれに基づいて安定な反応平面を持ついくつかの断片に分割し、各領域で局所的なLMPとMEPとを加重平均して一群の経路を発生させ、経路群の中で最小作用を与える経路をその領域におけるトンネル経路とし、各領域の局所トンネル経路を合成して全トンネル経路とする方法を提案した。この方法をheavy-light-heavy系であるNH_3+OH→NH_2+H_2Oに適用し、MEPより大きなトンネル確率を与える最適なトンネル経路を決定することが出来た。また、本トンネル...
  • 励起状態の反応ダイナミクス
  • Direct dynamics on electronic excited states

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  • ALP独自科目
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
  • 総合化学実験研究法
    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 実験法の原理的理解と応用 実験指導法 成果取りまとめとプレゼンテーション技法 論文執筆
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    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 実験指導法 ティーチングアシスタント
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    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : 計算化学、理論化学、分子軌道法、密度汎関数法
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    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 総合化学院
    キーワード : シュレディンガー方程式,分子軌道法,ハートリー・フォック方程式,密度汎関数理論,ボルン・オッペンハイマー近似,ポテンシャルエネルギー曲面,振動回転状態,遷移状態,反応経路,ダイナミクス,凝縮系,分子シミュレーション
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    キーワード : 分子軌道法,対称,分光学,表面,平衡と速度論
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    開講年度 : 2018年
    課程区分 : 修士課程
    開講学部 : 大学院共通科目
    キーワード : 分子軌道法,対称,分光学,表面,平衡と速度論
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    課程区分 : 博士後期課程
    開講学部 : 総合化学院
    キーワード : 実験法の改良・開発 実験指導法 成果とりまとめとプレゼンテーション技法 論文執筆 化学英語
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    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 量子化学計算、分子軌道法、プログラミング
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    開講年度 : 2018年
    課程区分 : 学士課程
    開講学部 : 理学部
    キーワード : 量子化学、分子軌道法

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  • 2014年4月1日 - 2016年3月31日 大学院総合化学院副学院長
  • 2018年4月1日 - 2020年3月31日 教育研究評議会評議員
  • 2018年4月1日 - 2020年3月31日 大学院総合化学院長


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