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Last Updated :2024/07/25

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Master

Affiliation (Master)

  • Faculty of Science　Earth and Planetary Sciences　Earth and Planetary System Science

Affiliation (Master)

  • Faculty of Science　Earth and Planetary Sciences　Earth and Planetary System Science

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Profile and Settings

Degree

  • Master of Science（Kyoto University）

Profile and Settings

  • Name (Japanese)

    Kawano

  • Name (Kana)

    Jun

  • Name

    200901071170051583

Alternate Names

Achievement

Research Interests

  • バイオミネラリゼーション   準安定相   分子シミュレーション   結晶成長   calcium carbonate   

Research Areas

  • Natural sciences / Biogeoscience
  • Nanotechnology/Materials / Crystal engineering
  • Natural sciences / Solid earth science

Education

  •        - 2000  Kyoto University
  •        - 2000  Kyoto University  Graduate School, Division of Natural Science
  •        - 1998  Kyoto University  Faculty of Science
  •        - 1998  Kyoto University  Faculty of Science

Awards

  • 2011/11 The Japanese Association for Crystal Growth 9th Young Researcher Award
     
    受賞者: KAWANO Jun

Published Papers

  • Yugo Kato, Woosuk Ha, Zehua Zheng, Lumi Negishi, Jun Kawano, Yoshihisa Kurita, Hitoshi Kurumizaka, Michio Suzuki
    Journal of Structural Biology 216 (2) 108074 - 108074 1047-8477 2024/06 [Refereed]
  • Ayako Shinozaki, Jun Kawano, Takaya Nagai
    The Journal of Physical Chemistry C 1932-7447 2024/03/29 [Refereed]
  • Harutoshi Asakawa, Itaru Echigo, Hiroshi Uneda, Ryo Kusaka, Koki Suga, Ryo Ikebe, Katsuo Tsukamoto, Jun Kawano, Hiroyasu Katsuno, Yoshihiro Nishimura, Takao Maki, Ryuichi Komatsu
    Journal of Crystal Growth 626 127482 - 127482 0022-0248 2024/01 [Refereed]
  • S. Motai, J. Kawano, S. Harii, Y. Seto, T. Watanabe, T. Nagai
    Journal of Geophysical Research: Biogeosciences 127 (2) 2169-8953 2022/02 [Refereed][Not invited]
     
    Skeletons of contemporary reef-building scleractinian corals are formed of aragonite, a polymorph of the calcium carbonate (CaCO3), notwithstanding calcite being a more stable phase under the condition of coral habitats. Circumstances developing aragonite in coral calcification have been addressed currently. Considering that the symbiotic relationship between the coral host and dinoflagellate algae (zooxanthellae) is perhaps relevant to coral calcification, we studied the impact of these symbiotic relationships on CaCO3 polymorph selection. Juvenile scleractinian corals (Acropora tenuis and Acropora digitifera) absent symbionts were cultured in seawaters with varied Mg/Ca molar ratios (mMg/Ca), and the mineral phases of the skeletons were detected employing X-ray diffraction. The findings revealed that diminutive quantities of calcite precipitated as coral skeleton in Acropora digitifera surprisingly in pseudo-present seawater (mMg/Ca similar to 5). Additionally, coral developed skeletons from only calcite in seawater with an mMg/Ca < 1. The evidence gathered in this investigation suggests that the symbiotic relationship affects the establishment of aragonite skeletons in the course of coral calcification.
  • Akira Tsuchiyama, Akira Miyake, Satoshi Okuzumi, Akira Kitayama, Jun Kawano, Kentaro Uesugi, Akihisa Takeuchi, Tsukasa Nakano, Michael Zolensky
    Science Advances 7 (17) 2021/04 [Refereed][Not invited]
  • 川野 潤
    月刊地球 42 (10) 533 - 536 2020/10 [Not refereed][Invited]
  • Ayaka Saito, Hiroyuki Kagi, Shiho Marugata, Kazuki Komatsu, Daisuke Enomoto, Koji Maruyama, Jun Kawano
    MINERALS 10 (3) 2020/03 [Refereed][Not invited]
     
    Calcite is a ubiquitous mineral in nature. Heavy alkaline-earth elements with large ionic radii such as Sr2+ and Ba2+ are highly incompatible to calcite. Our previous study clarified that incompatible Sr2+ ions can be structurally incorporated into calcite through crystallization from amorphous calcium carbonate (ACC). In this study, we synthesized Sr-doped calcite with Sr/(Sr + Ca) up to 30.7 +/- 0.6 mol% and Ba-doped calcite with Ba/(Ba + Ca) up to 68.6 +/- 1.8 mol%. The obtained Ba-doped calcite samples with Ba concentration higher than Ca can be interpreted as Ca-containing barium carbonates with the calcite structure which have not existed so far because barium carbonate takes the aragonite structure. X-ray diffraction (XRD) patterns of the Sr-doped and Ba-doped calcite samples obtained at room temperature showed that reflection 113 gradually weakened with increasing Sr/(Sr + Ca) or Ba/(Ba + Ca) ratios. The reflection 113 disappeared at Ba/(Ba + Ca) higher than 26.8 +/- 1.6 mol%. Extinction of reflection 113 was reported for pure calcite at temperatures higher than 1240 K, which was attributed to the rotational (dynamic) disorder of CO32- in calcite. Our Molecular Dynamics (MD) simulation on Ba-doped calcite clarified that the CO32- ions in Ba-doped calcites are in the static disorder at room temperature. The CO32- ions are notable tilted and displaced from the equilibrium position of pure calcite.
  • Jun Kawano, Takashi Toyofuki, Kaede Nishimura, Akiyuki Ueda, Yukiko Nagai, Sachiko Kawada, Henry Teng, Takaya Nagai
    Crystal Growth & Design 19 (8) 4212 - 4217 1528-7483 2019/07 [Refereed][Not invited]
     
    Copyright © 2019 American Chemical Society. Monitoring in situ local pH changes to dissolving/growing crystal surfaces is critical to decipher the related mechanisms. To date, however, reliable techniques to acquire such measurements remain under-developed. Here we report the first successful attempt to observe time-resolved, two-dimensional distribution of pH around crystals dissolving in aqueous solutions. The local pH change around dissolving calcium carbonate polymorphs (calcite and aragonite) was visualized by using the fluorescent probe 8-hydroxypyrene-1,3,6-trisul-fonic acid HPTS under an optical microscope. The observations unambiguously showed that pH increased and saturated rapidly immediately adjacent to the reactive surfaces on the cleavage rhombs of calcite. Approximately 1 mm away, however, the increase slowed down significantly, generating a steep pH gradient at the crystal-water interface. Aragonite, which has rough fractured surfaces in contrast to the well cleaved calcite, dissolved much faster and showed a stronger tendency for the pH profile to trace the outer shape of crystal grains. These results indicate that this technique is sensitive enough to detect small differences in dissolution between polymorphs and surface conditions and may be used as an effective tool to visualize and understand various reactions in aqueous solutions including environmental weathering and material erosion. ©
  • Jun-ya Tanaka, Jun Kawano, Takaya Nagai, Henry Teng
    Journal of Mineralogical and Petrological Sciences 114 (2) 105 - 109 1345-6296 2019/04 [Refereed][Not invited]
     
    Amorphous magnesium carbonate (AMC) is an important phase in the early formation stage of magnesium carbonate. In this study, precipitation experiments were conducted to clarify the formation and transformation process of AMC in aqueous solution. Fine AMC particles precipitated, immediately after mixing of Na2CO3 and MgCl2 solutions. Chemical composition of the AMC was determined to be approximately MgCO3 center dot 2H(2)O although two hydration states were expected to exist for AMCs. Subsequently, the AMC transformed in aqueous solutions into needle-like crystals of nesquehonite (MgCO3 center dot 3H(2)O), eventually to tiny polycrystalline particles of dypingite [Mg-5(CO3)(4)(OH)(2)center dot 5H(2)O] via a solvent-mediated processes.
  • Shinnosuke Ishizuka, Yuki Kimura, Jun Kawano, Rafael Escribano, Tomoya Yamazaki, Tetsuya Hama, Rikako Sato
    Journal of Physical Chemistry C 122 25092 - 25101 2018/10 [Refereed][Not invited]
  • Hiroshi SAKUMA, Henning O, SøRENSEN, Jun KAWANO, Nicolas BOVET, Keisuke FUKUSHI, Naoki NISHIYAMA, Hironori NAKAO
    Journal of Mineralogical and Petrological Sciences 113 232 - 244 2018/10 [Refereed][Not invited]
  • Yusuke Shibano, Kohei Takahata, Jun Kawano, Tsuyoshi Watanabe, Daisuke Enomoto, Hiroyuki Kagi, Natsumi Kamiya, Junji Yamamoto
    JOURNAL OF RAMAN SPECTROSCOPY 48 (12) 1755 - 1761 0377-0486 2017/12 [Refereed][Not invited]
     
    We investigated the relation between Sr# [=100Sr/(Sr+Ca) in mol] of calcites and their Raman spectra for Sr-doped calcite samples with Sr# of 0-13.2. We selected 3 major Raman peaks observed at 150-155cm(-1) (peak A), 274-282cm(-1) (peak B), and 710-712.5cm(-1) (peak C). With increasing Sr#, the peaks shifted monotonously to lower wavenumbers. We obtained a linear expression for peak B as Sr#=-1.734(B)+76.93, where (B) is a separation between peak B and a neon emission line of 237.07cm(-1) in Raman shift. The present spectroscopic analysis can ascertain Sr# of calcite with precision of +/- 1.26 in the range of Sr# of 0-13.2.
  • Keisuke Fukushi, Yuma Suzuki, Jun Kawano, Takeshi Ohno, Masahiro Ogawa, Toyonari Yaji, Yoshio Takahashi
    GEOCHIMICA ET COSMOCHIMICA ACTA 213 457 - 474 0016-7037 2017/09 [Refereed][Not invited]
     
    Monohydrocalcite (MHC: CaCO3 center dot H2O), a rare carbonate mineral formed under surface conditions, is usually observed in nature as containing a variable amount of Mg, with a 0.007-0.45 Mg/Ca mole ratio. The variable Mg composition in MHC is anticipated as a promising proxy to assess paleo-hydrochemistry especially in saline lakes. Although the roles of Mg on the formation and stability of MHC have been studied intensively, the Mg speciation in MHC has remained unclear and controversial. This study examined Mg speciation in MHC using X-ray absorption near edge structure (XANES), ab initio molecular simulation, and geochemical modeling. Mg-XANES spectra of MHC with different Mg/Ca ratios prepared from mixing solutions of Na2CO3, CaCl2 and MgCl2 revealed that the Mg in MHC is a mixture of amorphous Mg carbonate (AMC) and other Mg containing phase. The contribution of AMC to total Mg is negatively correlated to the crystallinity of MHC. Results show that AMC might play a protective role in the crystallization and the transformation to stable calcium carbonates. Ab initio calculation of Mg2+ substitution into MHC showed that a limited amount of Mg2+ can be incorporated into the MHC structure. Six-fold coordination of Mg2+ is substituted for eight-fold coordination of Ca2+ in the MHC structure. The other type of Mg in MHC revealed from the XANES analyses most likely corresponds to the structural Mg in MHC. The contribution of the structural Mg is almost constant at 0.06 in Mg/Ca, representing the limit of solid solubility of Mg in MHC. The solubility products of the MHC with the limit of solid solubility of Mg and the AMC associated with MHC were estimated from the reacted solution compositions. Prediction of the Mg/Ca ratio as a function of the initial solution conditions using solubility reasonably reproduces the observed apparent Mg/Ca ratios in MHC from the present study and earlier studies. The apparent Mg/Ca ratio of MHC is useful to elucidate water chemistry, especially for CO3/Ca and Mg concentrations during MHC formation. (C) 2017 Elsevier Ltd. All rights reserved.
  • KAWANO JUN, TENG HENRY
    日本結晶成長学会誌 日本結晶成長学会 44 (1) 17 - 24 2188-7268 2017/04/28 [Refereed][Invited]
     

      Recent studies for the early stages of crystal formation from aqueous solution have shown that crystals grow not only by the monomer-by-monomer addition mechanisms described in the classical nucleation theory, but also by the aggregation of particles, ranging from multi-ion complexes to fully formed nanocrytals. These particle-based growth processes have been considered as "non-classical" crystallization pathways and attracted research especially in the field of biomineralization for the last 20 years, however physical and chemical understanding for these processes is still lacking. Here we review literature reports on this mechanism to provide a general view for this new concept.

  • Fukushi Keisuke, Suzuki Yuma, Matsumiya Haruna, Kawano Jun, Ohno Takeshi, Ogawa Masahiro, Yaji Toyonari, Takahashi Yoshio
    Abstracts of Annual Meeting of the Geochemical Society of Japan 一般社団法人日本地球化学会 64 159 - 159 2017 

  • Hiroki Nada, Hitoshi Miura, Jun Kawano, Toshiharu Irisawa
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 62 (2) 404 - 407 0960-8974 2016/06 [Refereed][Not invited]
     
    This paper presents the outline of a practical course on computer simulation that will be given at the 16th International Summer School on Crystal Growth (ISSCG-16). The aim of this course is to understand crystal growth processes from the molecular level to the macroscopic level through computer simulations. We will mainly study molecular-scale crystal growth and nucleation processes by using molecular dynamics simulations and macroscopic growth processes at crystal surfaces by using phase field simulations. (C) 2016 Elsevier Ltd. All rights reserved.
  • Satoko Motai, Jun Kawano, Takaya Nagai, Kohki Sowa, Tsuyoshi Watanabe
    EUROPEAN JOURNAL OF MINERALOGY 28 (2) 265 - 271 0935-1221 2016/03 [Refereed][Not invited]
     
    Detailed observations of mineral phases in the skeleton of a massive reef-building coral were performed at nano- to micrometer scales using an analytical transmission electron microscope. The most notable result is the discovery of a nanosized halite (NaCl) phase coexisting with aragonite (CaCO3) in the coral skeleton. The halite grains are scattered not only along grain boundaries but also inside aragonite grains. The specific relationship of crystallographic orientations and microstructural features between halite and surrounding aragonite suggest that halite precipitated simultaneously with aragonite during calcification. The primary deposition of a mineral phase other than aragonite in a coral skeleton is confirmed for the first time.
  • Jun Kawano, Satoshi Maeda, Takaya Nagai
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 (4) 2690 - 2698 1463-9076 2016/01 [Refereed][Not invited]
     
    Mg2+ is considered to play an important role in the formation of calcium carbonate polymorphs; however, how it affects polymorph selection during the early stages of CaCO3 formation is not yet well understood. In the present study, in order to clarify the effect of Mg2+ on the nucleation of calcium carbonate polymorphs, the stable structures of anhydrous additive-free and Mg-containing calcium carbonate clusters are derived using the anharmonic downward distortion following method, based on quantum chemical calculations. Optimization is performed at the B3LYP/6-31+G(d) level and the solvent effect is induced by the self-consistent reaction field method using the conductor-like polarized continuum calculation model. Calculation results show that incorporating Mg2+ into clusters can change the clusters' stable configuration. In the case of dimers and trimers, a Mg ion strongly prefers to locate at the centre of the clusters, which suggests that Mg is easy to incorporate into the clusters once it is released from its tight hydration shell. Notably, structures similar to the crystalline phase appear when only four CaCO3 units aggregate into the cluster: in the stable structure of the additive-free CaCO3 tetramer, the arrangement of Ca and CO3 ions is almost the same as that of the calcite structure, while the structure of the Mg-containing CaCO3 tetramer resembles the aragonite structure in the way that CO3 ions are stacked. These results indicate that Mg can play a key role in aragonite formation not only by inhibiting calcite growth but also by directly promoting aragonite nucleation in the early stages of CaCO3 formation.
  • Jun Kawano, Muneyuki Okuyama, Takeshi Miyata
    Journal of Computer Chemistry, Japan 14 (4) 111 - 116 2015/11 [Refereed][Invited]
  • Jun Kawano, Hiroshi Sakuma, Takaya Nagai
    PROGRESS IN EARTH AND PLANETARY SCIENCE 2 7  2197-4284 2015/04 [Refereed][Not invited]
     
    First-principles calculations of Mg2+-containing aragonite surfaces are important because Mg2+ can affect the growth of calcium carbonate polymorphs. New calculations that incorporate Mg2+ substitution for Ca2+ in the aragonite {001} and {110} surfaces clarify the stability of Mg2+ near the aragonite surface and the structure of the Mg2+-containing aragonite surface. The results suggest that the Mg2+ substitution energy for Ca2+ at surface sites is lower than that in the bulk structure and that Mg2+ can be easily incorporated into the surface sites; however, when Mg2+ is substituted for Ca2+ in sites deeper than the second Ca2+ layer, the substitution energy approaches the value of the bulk structure. Furthermore, Mg2+ at the aragonite surface has a significant effect on the surface structure. In particular, CO3 groups rotate to achieve six-coordinate geometry when Mg2+ is substituted for Ca2+ in the top layer of the {001} surface or even in the deeper layers of the {110} surface. The rotation may relax the atomic structure around Mg2+ and reduces the substitution energy. The structural rearrangements observed in this study of the aragonite surface induced by Mg2+ likely change the stability of aragonite and affect the polymorph selection of CaCO3.
  • Lin Li, Takaya Nagai, Yusuke Seto, Kiyoshi Fujino, Jun Kawano, Shoich Itoh
    PHYSICS AND CHEMISTRY OF MINERALS 42 (2) 123 - 129 0342-1791 2015/02 [Refereed][Not invited]
     
    The silicate perovskite phase relation between CaSiO3 and MnSiO3 was investigated at 35-52 GPa and at 1,800 K using laser-heated diamond anvil cells combined with angle-dispersive synchrotron X-ray diffraction and energy-dispersive X-ray spectroscopic chemical analyses with scanning or transmission electron microscopy. We found that MnSiO3 can be incorporated into CaSiO3 perovskite up to 55, and 20 mol % of CaSiO3 is soluble in MnSiO3 perovskite. The range of 55-80 mol % of MnSiO3 in the CaSiO3-MnSiO3 perovskite system could be immiscible. We also observed that the two perovskite structured phases of the Mn-bearing CaSiO3 and the Ca-bearing MnSiO3 coexisted at these conditions. The Mn-bearing CaSiO3 perovskite has non-cubic symmetry and the Ca-bearing MnSiO3 perovskite has an orthorhombic structure with space group Pbnm. All the perovskite structured phases in the CaSiO3-MnSiO3 system convert to the amorphous phase during pressure release. MnSiO3 is the first chemical component confirmed to show such a superior solid solubility in CaSiO3 perovskite.
  • SAKUMA HIROSHI, KAWANO JUN
    地球化学 日本地球化学会 48 (1) 31 - 38 0386-4073 2014/03 [Refereed][Invited]
  • KAWANO JUN
    日本結晶成長学会誌 日本結晶成長学会 40 (4) 216 - 224 0385-6275 2014/01 [Refereed][Invited]
     
    Calcium carbonate, CaCO_3, occurs in six different forms: three crystalline polymorphs (calcite, aragonite, and vaterite), two hydrate phases, and amorphous calcium carbonate (ACC). These polymorphs are important both in the earth science, as rock-forming minerals, and in chemical technology, as raw materials for industrial processes. Furthermore, the occurrence of CaCO_3 in living organisms has received considerable attention. Therefore formation process of these polymorphs has been extensively investigated, however our knowledge is far from complete. In the present paper, we review how the formation process of CaCO_3 has been described in literatures, including a discovery that crystallization occurs through non-classical mechanism such as stable prenucletaion cluster aggregation (Gebauer et al.: Science, 322, 1819), which give a new picture of the early stages of calcium carbonate growth.
  • Jun Kawano, Yoshihiro Kangawa, Tomoe Yayama, Koichi Kakimoto, Akinori Koukitu
    JAPANESE JOURNAL OF APPLIED PHYSICS 52 (4)  - KJ001094 0021-4922 2013/04 [Refereed][Not invited]
     
    Thermodynamic analysis of coherently grown GaAs1-xNx on Ge with low N content was performed to determine the relationship between solid composition and growth conditions. In this study, a new algorithm for the simulation code, which is applicable to wider combinations of gaseous sources than the traditional algorithm, was developed to determine the influence of different gaseous sources on N incorporation. Using this code, here we successfully compared two cases: one is a system using trimethylgallium (TMG), AsH3, and NH3, and the other uses dimethylhydrazine (DMHy) instead of NH3. It was found that the optimal N/As ratio of input gas in the system using DMHy was much lower than that using NH3. This shows that the newly developed algorithm could be a useful tool for analyzing the N incorporation during the vapor growth of GaAs1-xNx. (C) 2013 The Japan Society of Applied Physics
  • Satoko Motai, Takaya Nagai, Kohki Sowa, Tsuyoshi Watanabe, Naoya Sakamoto, Hisayoshi Yurimoto, Jun Kawano
    Journal of structural biology 180 (3) 389 - 93 1047-8477 2012/12 [Refereed][Not invited]
     
    The skeletal texture and crystal morphology of the massive reef-building coral Porites lobata were observed from the nano- to micrometer scale using an analytical transmission electron microscope (ATEM). The skeletal texture consists of centers of calcification (COCs) and fiber area. Fiber areas contain bundles of needle-like aragonite crystals that are elongated along the crystallographic c-axis and are several hundred nanometers to one micrometer in width and several micrometers in length. The size distribution of aragonite crystals is relatively homogeneous in the fibers. Growth lines are observed sub-perpendicular to the direction of aragonite growth. These growth lines occur in 1-2 μm intervals and reflect a periodic contrast in the thickness of an ion-spattered sample and pass through the interior of some aragonite crystals. These observations suggest that the medium filled in the calcification space maintains a CaCO₃-supersaturated state during fiber growth and that a physical change occurs periodically during the aragonite crystals of the fiber area.
  • Jun Kawano, Yoshihiro Kangawa, Koichi Kakimoto
    JAPANESE JOURNAL OF APPLIED PHYSICS 51 (10)  - KJ001094 0021-4922 2012/10 [Refereed][Not invited]
     
    First-principles calculations of GaAsN surface with low nitrogen (N) content grown by chemical beam epitaxy were performed to theoretically analyze the incorporation process of nitrogen and impurities at the atomic scale. As a result, stable surface structures of GaAsN(001) under hydrogen (H) atmosphere were determined. In these structures, N is suggested to readily substitute into surface sites, especially those that bond with H, compared with in the bulk. This indicates that N is incorporated into a thin film together with H. This may generate H-related defects, which may lead to the degradation of its electric properties. These defects are difficult to minimize by post-annealing processes. Therefore, the amount of H attached to the growth surface should be reduced in order to obtain high-quality crystals. The calculated surface phase diagram suggests that a condition in which the extent of the incorporation of H-related defects can be reduced exists. (C) 2012 The Japan Society of Applied Physics
  • Jun Kawano, Yoshihiro Kangawa, Tomonori Ito, Koichi Kakimoto, Akinori Koukitu
    JOURNAL OF CRYSTAL GROWTH 343 (1) 105 - 109 0022-0248 2012/03 [Refereed][Not invited]
     
    In this paper, we use thermodynamic analysis to determine how the nitrogen (N) ratio in the source gases affects the solid composition of coherently grown GaAs1-xNx(x similar to 0.03). The source gases for Ga, As, and N are trimethylgallium ((CH3)(3)Ga), arsine (AsH3), and ammonia (NH3), respectively. The growth occurs on a Ge substrate, and the analysis includes the stress from the substrate-crystal lattice mismatch. Calculation results indicate that to have just a few percent N incorporation into the grown solid, the V/III ratio in the source gases should be several thousands and the input-gas partial-pressure ratio NH3/(NH3+AsH3) should exceed 0.99. We also find that the lattice mismatch stress from the Ge substrate increases the V/III source-gas ratio required for stable growth, whereas an increase in input Ga partial pressure ratio has the opposite effect. (C) 2012 Elsevier B.V. All rights reserved.
  • KAWANO JUN, KANGAWA YOSHIHIRO, YAYAMA TOMOE, ITO TOMONORI, KAKIMOTO KOICHI, KOKITSU AKINORI
    日本結晶成長学会誌 38 (2) 128 - 136 0385-6275 2011/07 [Refereed][Invited]
  • Jun Kawano, Yoshihiro Kangawa, Tomoe Yayama, Tomonori Ito, Koichi Kakimoto, Akinori Koukitu
    Conference Record of the IEEE Photovoltaic Specialists Conference 000496 - 000500 0160-8371 2011 [Not refereed][Not invited]
     
    Thermodynamic analysis was performed to investigate the coherent growth of GaAs 1-xN x thin films with low N content. In the present study, a new algorithm of the simulation code was developed to theoretically predict the relationship between solid composition and growth condition. This algorithm is applicable to wider varieties of combinations of gaseous sources than is the traditional algorithm. The system using trimethylgalllium (TMG), AsH 3, and NH 3 was analyzed with the new code, and the results showed that the required input partial pressure ratio of NH 3 to the group-V element is over 99% for incorporation of a small percent of N into a solid. It is difficult to incorporate N into the solid when the input V/III ratio is low, while in the case of a high input V/III ratio, stable growth with a small percent of N can proceed. In the case of coherently grown GaAs 1-xN x, the lattice constraint from the substrate would suppress the incorporation of nitrogen. On the other hand, a higher input Ga partial pressure ratio enhances the stable growth of GaAs 1-xN x with a small N content, though this condition tends to easily induce generation of dislocations. Furthermore, a much lower optimum N/As ratio in input gas can be achieved in the system with dimethylhydrazine (DMHy). This result confirms that the difference in gaseous sources has a great effect on N incorporation. When determining well-optimized experimental growth conditions, these influences including crystallinity should all be considered. © 2011 IEEE.
  • Akira Miyake, Jun Kawano
    JOURNAL OF PHYSICS-CONDENSED MATTER 22 (22)  - KJ001094 0953-8984 2010/06 [Refereed][Not invited]
     
    For molecular dynamics simulations using aragonite structure as the initial state, a new phase of space group P6(3)22 (hexagonal aragonite) appeared at temperatures above 510 K at a pressure of 1 atm. It was a first-order phase transition which occurs metastably within the stable region of calcite and the dT/dP slope of the phase boundary between orthorhombic and hexagonal aragonite was about 1.25 x 10(3) K GPa(-1). In the hexagonal aragonite structure, CO(3) groups were rotated by 30 degrees around the c axis and move up and down along the c axis from their position in aragonite, and Ca ions were six-coordinated as they are in calcite. The CaO(6) octahedron of hexagonal aragonite was strongly distorted, whereas in the calcite structure it is an almost ideal octahedron. The transition between hexagonal and orthorhombic aragonite involves only small movements of CO(3) groups. Therefore, it is possible that hexagonal aragonite plays an important part in the metastable formation of aragonite within the stability field of calcite and in the development of sector trilling in aragonite.
  • Identification of CVD-grown synthetic melee pink diamond
    Hiroshi Kitawaki, Ahmadjan Abduriyim, Jun Kawano, Makoto Okano
    The Journal of Gemmology 32 23 - 30 2010 [Refereed][Not invited]
  • Jun Kawano, Norimasa Shimobayashi, Akira Miyake, Masao Kitamura
    JOURNAL OF PHYSICS-CONDENSED MATTER 21 (42)  - KJ001094 0953-8984 2009/10 [Refereed][Not invited]
     
    In order to interpret the formation mechanism of calcium carbonate polymorphs, we propose and construct a new 'precipitation diagram', which has two variables: the driving force for nucleation and temperature. The precipitation experiments were carried out by mixing calcium chloride and sodium carbonate aqueous solutions. As a result, a calcite-vaterite co-precipitation zone, a vaterite precipitation zone, a vaterite-aragonite co-precipitation zone and an aragonite precipitation zone can be defined. Theoretical considerations suggest that the steady state nucleation theory can explain well the appearance of these four zones, and the first-order importance of the temperature dependency of surface free energy in the nucleation of aragonite. Furthermore, the addition of an impurity will likely result in the change of these energies, and this precipitation diagram gives a new basis for interpreting the nature of the polymorphs precipitated in both inorganic and biological environments.
  • Jun Kawano, Akira Miyake, Norimasa Shimobayashi, Masao Kitamura
    JOURNAL OF PHYSICS-CONDENSED MATTER 21 (27)  - KJ001094 0953-8984 2009/07 [Refereed][Not invited]
     
    Molecular dynamics (MD) simulation of calcium carbonate at high pressure was performed to understand the phase transition between calcite (R (3) over barc) and CaCO3-II (P2(1)/c). In the 300-800 K temperature range, the transition of calcite to CaCO3-II was reproduced at a pressure of around 8 GPa. This transition is of first order and reversible in the MD calculations except for runs at 300 K where a small hysteresis exists. The slope of the dP/dT curve at the phase boundary between calcite and CaCO3-II is negative at 300 K and turns positive at around 600 K, which was confirmed by analyzing the enthalpy change. Just below the transition pressure, the P2(1)/c structure appears and its orientation switches among three positions with time, resulting in the maintenance of the R (3) over barc structure as a whole. The P2(1)/c structure resembles the structure of CaCO3-II on an increase of temperature. It can be suggested that the existence of the P2(1)/c structure and the switching of its orientation just below the transition pressure are responsible for the change of the slope of the dP/dT curve at the boundary from negative to positive on an increase of temperature, because the switching increases entropy and results in an expansion of the stability field of calcite.
  • Jun Kawano, Akira Miyake, Norimasa Shimobayashi, Masao Kitamura
    JOURNAL OF PHYSICS-CONDENSED MATTER 21 (9)  - KJ001094 0953-8984 2009/03 [Refereed][Not invited]
     
    Molecular dynamics ( MD) simulation of calcite was carried out with the interatomic potential model based on ab initio calculations to elucidate the phase relations for calcite polymorphs and the mechanism of the rotational order-disorder transition of calcite at high temperature at the atomic scale. From runs of MD calculations with increasing temperature within a pressure range of 1 atm and 2 GPa, the transition of calcite with R (3) over barc symmetry into a high-temperature phase with R (3) over barm symmetry was reproduced. In the high-temperature R (3) over barm phase, CO(3) groups vibrate with large amplitudes either around the original positions in the R (3) over barc structure or around other positions rotated +/- 60 degrees, and their positions change continuously with time. Moreover, contrary to the suggestion of previous investigators, the motion of CO(3) groups is not two-dimensional. At 1 atm, the transition between R (3) over barc and R (3) over barm is first order in character. Upon increasing temperature at high pressure, however, first a first-order isosymmetric phase transition between the R (3) over barc phases occurs, which corresponds to the start of +/- 120 degrees flipping of CO(3) groups. Then, at higher temperatures, the transition of R (3) over barc to R (3) over barm phases happens, which can be considered second order. This set of two types of transitions at elevated pressure can be characterized by the appearance of an 'intermediate' R (3) over barc phase between the stable region of calcite and the high-temperature R (3) over barm phase, which may correspond to the CaCO(3)-IV phase.
  • Treated CVD-grown pink synthetic diamond mele
    Hiroshi Kitawaki, Ahmadjan Abduriyim, Jun Kawano, Makoto Okano
    Gems & Gemology 45 68 - 69 2009 [Refereed][Not invited]
  • KAWANO JUN, MIYAKE AKIRA
    月刊地球 148 - 152 0387-3498 2005/07/01 [Not refereed][Not invited]
  • A Miyake, J Kawano
    GEOPHYSICAL RESEARCH LETTERS 32 (13) 1 - 4 0094-8276 2005/07 [Refereed][Not invited]
     
    The seismic velocities for three kinds of enstatite (low clinoenstatite, L-CEn; orthoenstatite, OEn; and high-pressure clinoenstatite, HP-CEn), which is a major component in the upper mantle, were estimated using molecular dynamics simulations based on the interatomic potential model. The calculated seismic velocities, V-p and V-s, for OEn are slower than those of L-OEn up to 6 GPa and 1000 K. The velocities in HP-CEn are faster than those in OEn at the transition pressure between OEn and HP-CEn. Furthermore, anisotropy of the seismic velocity, in particular Vp parallel to [100] > [001] > [010], is observed. We conclude that the transitions in enstatites are related to the seismic discontinuity observed at depths less than 410 km and that enstatite is as an important a mineral as olivine for the mineralogical model and for the anisotropic propagation of seismic waves in the Earth's upper mantle.
  • M. Matsumoto, S. Wallis, M. Aoya, M. Enami, J. Kawano, Y. Seto, N. Shimobayashi
    Journal of Metamorphic Geology 21 (4) 363 - 376 0263-4929 2003 [Refereed][Not invited]
     
    A largely undocumented region of eclogite associated with a thick blueschist unit occurs in the Kotsu area of the Sanbagawa belt. The composition of coexisting garnet and omphacite suggests that the Kotsu eclogite formed at peak temperatures of around 600 °C synchronous with a penetrative deformation (D1). There are local significant differences in oxygen fugacity of the eclogite reflected in mineral chemistries. The peak pressure is constrained to lie between 14 and 25 kbar by microstructural evidence for the stability of paragonite throughout the history recorded by the eclogite, and the composition of omphacite in associated eclogite facies pelitic schist. Application of garnet-phengite-omphacite geobarometry gives metamorphic pressures around 20 kbar. Retrograde metamorphism associated with penetrative deformation (D2) is in the greenschist facies. The composition of syn-D2 amphibole in hematite-bearing basic schist and the nature of the calcium carbonate phase suggest that the retrograde P-T path was not associated with a significant increase or decrease in the ratio of P-T conditions following the peak of metamorphism. This P-T path contrasts with the open clockwise path derived from eclogite of the Besshi area. The development of distinct P-T paths in different parts of the Sanbagawa belt shows the shape of the P-T path is not primarily controlled by tectonic setting, but by internal factors such as geometry of metamorphic units and exhumation rates.
  • J Kawano, N Shimobayashi, M Kitamura, K Shinoda, N Aikawa
    JOURNAL OF CRYSTAL GROWTH 237 419 - 423 0022-0248 2002/04 [Refereed][Not invited]
     
    The precipitation process of calcium carbonate front highly supersaturated solutions was observed in situ by mixing CaCl2 and Na2CO3 aqueous solutions at about 20degreesC under an optical microscope and an infrared microspectroscope. After an amorphous phase forms, spherulitic vaterite and calcite in a rhombohedral shape nucleate simultaneously but separately, and grow by forming the precipitate-free zone around them. This transformation is solvent-mediated, and the measurement of the growth rate suggests that the rate-control ling process is the diffusion of elements in the earlier stage of this process, which then changes to surface kinetics. (C) 2002 Elsevier Science B.V. All rights reserved.

MISC

Presentations

Association Memberships

  • JAPANESE ASSOCIATION FOR CRYSTAL GROWTH   THE JAPAN SOCIETY OF APPLIED PHYSICS   日本コンピュータ化学会   分子シミュレーション研究会   日本鉱物学会   

Research Projects

  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 2023/04 -2027/03 
    Author : 鈴木 道生, 安元 剛, 長井 裕季子, 豊福 高志, 川野 潤, 竹内 猛
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (S)
    Date (from‐to) : 2020/08 -2025/03 
    Author : 木村 勇気, 瀧川 一学, 川野 潤, 田中 今日子
     
    本研究課題は、水溶液からの核生成の透過型電子顕微鏡“その場”観察実験を軸に、水和層の役割を理解するために、水和層の無い気相からの核生成実験などを対照実験として実施する。水溶液からの核生成の透過型電子顕微鏡“その場”観察実験では、溶液試料を観察できる3つの手法（窓板ホルダー、溶液セル、グラフェン膜）から、核生成のその場観察に最も適した手法として初年度に選定を行った窓板ホルダーを用いて、機械学習による核生成の予測に必須の教師データの取得を行った。その結果、低電子線画像と高電子線画像をそれぞれ1,000枚取得して教師画像セットを準備することで低電子線量で得た暗い像を電子線量にして1万倍程度明るくすることに成功した。さらに、溶液から核生成する粒子を早期に検出することにも成功した。また、電子線が溶媒である水を放射性分解することで、結晶化条件が変化してしまうことをできるだけ避けるために、電子線をパルス化するシステムを導入した。テスト試料としてステアリン酸結晶の電子線損傷を調べた結果、照射時間が10%になるようにパルス幅を調整した所、結晶の寿命は10倍以上に延びる結果が得られており、想定以上に効果があることが分かった。 溶液からの核生成では、水和層が重要な役割を果たしていると考えられている。そこで、初年度に引き続き、水和層のない気相からの核生成実験を行い、その過程を干渉計でその場観察して核生成時の温度、圧力と過飽和度増加の時間スケールから核生成理論式に必須の物理量を炭素、チタン、炭化チタンに対して求めて論文を投稿した。
  • 日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)
    Date (from‐to) : 2021/07 -2023/03 
    Author : 川野 潤
     
    本研究は、研究代表者が近年開発した、反応界面における局所的なpHおよびCaイオン濃度変化を蛍光プローブを用いて可視化する技術を、多様な材料に適用できるように高精度化・汎用化することを目的としている。2022年度においては、以下について研究を進め、成果を得ている。 [1]ゲル内二重拡散法によって合成される炭酸カルシウムについて、形成環境のpHの可視化に成功した。ゲル全体のpH変化を可視化した結果、多形によって形成環境のpHの変化の傾向が異なることが明らかになった。さらにレーザー共焦点顕微鏡を用いた詳細な観察により、カルサイト成長時の結晶近傍のpHに局所的な不均一が生じることを初めて確認した。しかし、アラゴナイト形成場の近傍にはこのような傾向は観察されず、このような形成場の局所的な環境の違いも多形形成に影響を与えている可能性が示唆された。 [2]従来までに観察可能であることが示されている炭酸カルシウム以外の材料についての適用を進めた。特に、リン酸カルシウム系の材料について、溶解時のpH変化およびCaイオン濃度分布の変化を可視化したところ、アパタイトやリン酸八カルシウムなど、物質によって異なる傾向を示すことが観察された。さらに、同じ物質であっても、Naが含有しているものは、含有していないものとは大きく異なるpH変化の傾向を示すことが明らかになった。このことは、生体材料としてリン酸カルシウムを用いたり、生体内でのリン酸カルシウムの形成過程を理解する際の指針となる。
  • 文部科学省：科学研究費補助金（基盤研究(B))
    Date (from‐to) : 2019 -2022 
    Author : 鈴木 道生
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2020/04 -2021/03 
    Author : 木村 勇気, 瀧川 一学, 川野 潤, 田中 今日子
     
    核生成は物質形成の最初期のプロセスであり、科学から産業に至る様々な分野の鍵となるにもかかわらず、その理解は極めて限定的である。これは、核生成がナノ領域で高速に、かつ確率的におこる現象で実空間観察が非常に困難なためである。 本研究では、「安定核の生成までに何が起こっているのか？」、「安定核の生成ルートはどのように決まるのか？」を核心をなす問いに据え、溶液中の核生成に影響する各因子の寄与の程度と物質依存性を明らかにし、核生成ルートを決めるキーファクターに制限を加えることを目的に研究を行った。キーファクターは、核生成理論式に必須の“核と水の界面エネルギー”とカイネティック係数(分子の取り込まれやすさ)、ダイマーの形成、脱水和や粘性、界面近傍のpHやイオン濃度、ナノ粒子特有の物性などである。 TEM観察では、結晶の成長速度、形、集合、配列、サイズなどを直接観察でき、加えて電子回折パターンで相同定も同時に行えるため、核生成の理解に対して飛躍的な成果が見込める。そのため、目的の達成には溶液から前駆体を経て結晶ができるまでの核生成過程の一部始終をTEMにより実空間で可視化するのが最も近道であると考えている。本研究課題の間には、TEM観察するうえでボトルネックとなっている、確率的な核生成現象を偶然に頼って観察している状況に対し、機械学習を取り入れることで核生成の時間と場所を予測して能動的に核生成の一部始終をTEM観察するという革新的な手法の構築に取り組んだ。その結果、人間の眼で判断するよりも早く核生成を捉えることに成功した。この研究は基盤研究（S）に発展的内容で引き継がれた。
  • 文部科学省：科学研究費補助金（基盤研究(B))
    Date (from‐to) : 2019 -2021 
    Author : 川野 潤
  • 文部科学省：科学研究費補助金(基盤研究(Ｓ))
    Date (from‐to) : 2015 -2019 
    Author : 木村勇気
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2013/06 -2018/03 
    Author : KOUCHI Akira, KAWANO Jun
     
    To understand the formation and evolution mechanism of molecules in interstellar molecular clouds, we have performed experiments on surface atomic reactions and photochemical reactions. In surface atomic reaction experiments, we have clarified formation and H/D fractionation mechanism of important molecules and succeeded to draw general description of quantum tunneling reactions. Furthermore, we observed surface structure of amorphous ice by atomic force microscope and showed that water molecule formed at 10 K shows a statistical high-temperature ortho/para ratio of 3, invalidating the assumed relation between ortho/para ratio and temperature. In photochemical reaction experiments, we observed organic refractory residue by some microscopes and found singular texture which was found in interplanetary dusts and some primitive meteorites. We also found that UV-irradiated amorphous ices behave like liquid at temperatures between 50 and 150 K.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2014 -2016 
    Author : KAWANO JUN
     
    Formation process of aragonite, high-pressures polymorph of calcium carbonate, has been extensively investigated for long time because it is one of the most important biominerals. In the present study, we focused on the effect of magnesium (Mg) on the polymorph selection during the early stages of calcium carbonate formation, and theoretically derived the stable structures of anhydrous additive-free and Mg-containing calcium carbonate clusters based on quantum chemical calculations. Results show the incorporation of Mg into clusters can change stable configuration of clusters, and that the stable structure of Mg-containing tetramer resembles aragonite structure in the stacking manner of carbonate ions. These results indicate that Mg can directly promote aragonite formation in the early stages of calcium carbonate formation, once it is released from its tight hydration shell. Therefore, it can be possible that the dehydration of Mg is a key process for the polymorph selection.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2013 -2015 
    Author : Tachibana Shogo, Akira Miyake, Naoya Sakamoto, Jun Kawano
     
    Vapor growth experiments on forsterite, a major silicate mineral in space, were conducted under controlled protoplanetary disk conditions in order to understand its vapor growth kinetics. The growth experiments of forsterite at 1350 K in the presence of hydrogen gas (5 Pa) containing H2O (H2O/H2=0.05) were done at the supersaturation ratio of 15-20, and we found that the condensation coefficient of forsterite, a non-dimension parameter representing kinetic hindrance for vapor growth, is in the range of 0.003-0.006.
  • Formation Process of Calcium Carbonate Polymorphs

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