Researcher Profile and Settings

Profile and Settings

Name

• Name

  TAHARA Shuta

Affiliations

Affiliation (Master)

• Professor

Education, Etc.

Education

• Apr. 2001, Mar. 2005
• Apr. 2008, Mar. 2011
• Apr. 2005, Mar. 2007
• Apr. 2008, Mar. 2011, Kyushu University, Department of physics
• Apr. 2005, Mar. 2007, Kyushu University, Department of Chemistry and physics of Condensed Matter
• Apr. 2001, Mar. 2005, Kyushu University, Faculty of Science, Department of physics

Degree

• Mar. 2007
• Mar. 2011
• Kyushu University

その他基本情報

Association Memberships

• The Solid State Ionics Society of Japan
• Physical Society of Japan

Committee Memberships

• Nov. 2020, Sep. 2022
• Nov. 2018, May 2019
• Oct. 2015, Sep. 2016
• Apr. 2013, Mar. 2015
• Feb. 2013
• Dec. 2012
• Nov. 2011

Academic & Professional Experience

• Apr. 2024, 9999, Chukyo University, Professor
• Nov. 2016, Mar. 2024, University of the Ryukyus, Faculty of Science, Department of Physics and Earth Sciences, Associate Professor
• May 2017, Mar. 2020
• Apr. 2013, Mar. 2019
• 01 Jan. 2016, 30 Apr. 2017
• 01 Apr. 2011, 31 Oct. 2016, University of the Ryukyus, Faculty of Science, Department of Physics and Earth Sciences, Assistant Professor
• 01 Apr. 2007, 31 Mar. 2011, Niigata University of Pharmacy and Applied Life Sciences, Laboratory of Physics, Research Associate

Research Activities

Book, papers, etc

Published Papers

• Intermolecular Correlations in Liquid Lactic Acid Based on ab initio Molecular Dynamics Simulations Combined with High-Energy X-ray Diffraction Measurements
  J. Phys. Soc. Jpn, 93, 054601_1, 054601_7, Apr. 2024
• Lithium Ion Transport Environment by Molecular Vibrations in Ion‐Conducting Glasses
  Hiroki Yamada; Koji Ohara; Satoshi Hiroi; Atsushi Sakuda; Kazutaka Ikeda; Takahiro Ohkubo; Kengo Nakada; Hirofumi Tsukasaki; Hiroshi Nakajima; Laszlo Temleitner; Laszlo Pusztai; Shunsuke Ariga; Aoto Matsuo; Jiong Ding; Takumi Nakano; Takuya Kimura; Ryo Kobayashi; Takeshi Usuki; Shuta Tahara; Koji Amezawa; Yoshitaka Tateyama; Shigeo Mori; Akitoshi Hayashi
  Energy Environ. Mater., 0, e12612_1, e12612_10, 31 Mar. 2023
• Crystal Growth, Structural and Thermal Studies of FeC4H4O6·2.5H2O
  Takanori Fukami; Shuta Tahara
  14, 2, 8, 17, 04 Jul. 2022, Single crystals of iron(II) tartrate hemi-pentahydrate, FeC4H4O6·2.5H2O, were grown by the gel method using silica gels. Differential scanning calorimetry, thermogravimetric-differential thermal analysis, and X-ray diffraction measurements were performed on the single crystals. The space group symmetry (orthorhombic P212121) and structural parameters were determined at room temperature. The crystal structure consisted of slightly distorted FeO6 octahedra, C4H4O6 and H2O molecules, C4H4O6–Fe–C4H4O6 chains jointed by Fe–O bonds, and O–H···O hydrogen-bonding frameworks between adjacent molecules. Weight losses due to thermal decomposition of the crystal were found to occur in the temperature range of 300–1060 K. We inferred that the weight losses were caused by the evaporation of bound water molecules and the evolution of H2CO, CO, and O2 gases from C4H4O6 molecules, and that the black residue after decomposition was composed of triiron tetraoxide (Fe3O4) and carbon.
• Structure of alumina glass
  Hideki Hashimoto; Yohei Onodera; Shuta Tahara; Shinji Kohara; Koji Yazawa; Hiroyo Segawa; Motohiko Murakami; Koji Ohara
  12, 1, Jan. 2022, The fabrication of novel oxide glass is a challenging topic in glass science. Alumina (Al₂O₃) glass cannot be fabricated by a conventional melt–quenching method, since Al₂O₃ is not a glass former. We found that amorphous Al₂O₃ synthesized by the electrochemical anodization of aluminum metal shows a glass transition. The neutron diffraction pattern of the glass exhibits an extremely sharp diffraction peak owing to the significantly dense packing of oxygen atoms. Structural modeling based on X-ray/neutron diffraction and NMR data suggests that the average Al–O coordination number is 4.66 and confirms the formation of OAl₃ triclusters associated with the large contribution of edge-sharing Al–O polyhedra. The formation of edge-sharing AlO₅ and AlO₆ polyhedra is completely outside of the corner-sharing tetrahedra motif in Zachariasen’s conventional glass formation concept. We show that the electrochemical anodization method leads to a new path for fabricating novel single-component oxide glasses.
• Structural and Thermal Investigations of L-CuC4H4O6·3H2O and DL-CuC4H4O6·2H2O Single Crystals
  Takanori Fukami; Shuta Tahara
  International Journal of Chemistry, 13, 1, 38, 38, 10 Apr. 2021, Copper(II) L-tartrate trihydrate, L-CuC4H4O6·3H2O, and copper(II) DL-tartrate dihydrate, DL-CuC4H4O6·2H2O, crystals were grown at room temperature by the gel method using silica gels as the growth medium. Differential scanning calorimetry, thermogravimetric-differential thermal analysis, and X-ray diffraction measurements were performed on both crystals. The space group symmetries (monoclinic P21 and P21/c) and structural parameters of the crystals were determined at room temperature and at 114 K. Both structures consisted of slightly distorted CuO6 octahedra, C4H4O6 and H2O molecules, C4H4O6–Cu–C4H4O6 chains linked by Cu–O bonds, and O–H–O hydrogen-bonding frameworks between adjacent molecules. Weight losses due to thermal decomposition of the crystals were found to occur in the temperature range of 300–1250 K. We inferred that the weight losses were caused by the evaporation of bound water molecules and the evolution of H2CO, CO, and O2 gases from C4H4O6 molecules, and that the residual reddish-brown substance left in the vessels after decomposition was copper(I) oxide (Cu2O).
• Mode Distribution Analysis for Superionic Melt of CuI by Coherent Quasielastic Neutron Scattering
  Yukinobu Kawakita; Tatsuya Kikuchi; Shuta Tahara; Mitsutaka Nakamura; Yasuhiro Inamura; Kenji Maruyama; Yasuhiro Yamauchi; Seiko Ohira-Kawamura; Kenji Nakajima
  JPS Conf. Proc., 33, 011071_1, 011071_6, 26 Mar. 2021
• ガラスにならないEr2O3液体が持つ特異構造
  小山千尋; 小原真司; 田原周太; 小野寺陽平; 石川毅彦
  放射光, 34, 30, 36, Jan. 2021
• Structure and properties of densified silica glass: characterizing the order within disorder
  Yohei Onodera; Shinji Kohara; Philip S. Salmon; Akihiko Hirata; Norimasa Nishiyama; Suguru Kitani; Anita Zeidler; Motoki Shiga; Atsunobu Masuno; Hiroyuki Inoue; Shuta Tahara; Annalisa Polidori; Henry E. Fischer; Tatsuya Mori; Seiji Kojima; Hitoshi Kawaji; Alexander I. Kolesnikov; Matthew B. Stone; Matthew G. Tucker; Marshall T. McDonnell; Alex C. Hannon; Yasuaki Hiraoka; Ippei Obayashi; Takenobu Nakamura; Jaakko Akola; Yasuhiro Fujii; Koji Ohara; Takashi Taniguchi; Osami Sakata
  NPG Asia Materials, 12, 1, 85-1, 85-16, Dec. 2020, The broken symmetry in the atomic-scale ordering of glassy versus crystalline solids leads to a daunting challenge to provide suitable metrics for describing the order within disorder, especially on length scales beyond the nearest neighbor that are characterized by rich structural complexity. Here, we address this challenge for silica, a canonical network-forming glass, by using hot versus cold compression to (i) systematically increase the structural ordering after densification and (ii) prepare two glasses with the same high-density but contrasting structures. The structure was measured by high-energy X-ray and neutron diffraction, and atomistic models were generated that reproduce the experimental results. The vibrational and thermodynamic properties of the glasses were probed by using inelastic neutron scattering and calorimetry, respectively. Traditional measures of amorphous structures show relatively subtle changes upon compacting the glass. The method of persistent homology identifies, however, distinct features in the network topology that change as the initially open structure of the glass is collapsed. The results for the same high-density glasses show that the nature of structural disorder does impact the heat capacity and boson peak in the low-frequency dynamical spectra. Densification is discussed in terms of the loss of locally favored tetrahedral structures comprising oxygen-decorated SiSi₄ tetrahedra.
• Very sharp diffraction peak in non-glass forming liquid with the formation of distorted tetraclusters
  C. Koyama; S. Tahara; S. Kohara; Y. Onodera; D. R. Småbråten; S. M. Selbach; J. Akola; T. Ishikawa; A. Masuno; A. Mizuno; J. T. Okada; Y. Watanabe; Y. Nakata; K. Ohara; H. Tamaru; H. Oda; I. Obayashi; Y. Hiraoka; O. Sakata
  NPG Asia Materials, 12, 43-1, 43-11, Jun. 2020
• Controlling the oxygen coordination and valence of the network forming cation for excellent glass properties
  T. Aoyagi; S. Kohara; T. Naito; Y. Onodera; M. Kodama; T. Onodera; D. Takamatsu; S. Tahara; O. Sakata; T. Miyake; K. Suzuya; K. Ohara; T. Usuki; Y. Hayashi; H. Takizawa
  Sci. Rep., 10, 7178_1, 7178_12, Apr. 2020
• Accurate Synchrotron Hard X-ray Diffraction Measurements on High-Temperature Liquid Oxides
  K. Ohara; Y. Onodera; S. Kohara; C. Koyama; A. Masuno; A. Mizuno; J. T. Okada; S. Tahara; Y. Watanabe; H. Oda; Y. Nakata; H. Tamaru; T. Ishikawa; O. Sakata
  Int. J. Microgravity Sci. Appl., 37, 2, 370202–1, 370202–7, Apr. 2020
• Crystal Structures and Thermal Properties of L-MnC4H4O6·2H2O and DL-MnC4H4O6·2H2O
  T. Fukami; S. Tahara
  Int. J. Chem., 12, 78, 88, Jan. 2020
• Understanding diffraction patterns of glassy, liquid and amorphous materials via persistent homology analyses
  Y. Onodera; S. Kohara; S. Tahara; A. Masuno; H. Inoue; M. Shiga; A. Hirata; K. Tsuchiya; Y. Hiraoka; I. Obayashi; K. Ohara; A. Mizuno; Y. Katsuya; O. Sakata
  J. Ceram. Soc. Jpn., 127, 12, 853, 863, Dec. 2019, The structure of glassy, liquid, and amorphous materials is still not well understood, due to the insufficient structural information from diffraction data. In this article, attempts are made to understand the origin of diffraction peaks, particularly of the first sharp diffraction peak (FSDP, Q(1)), the principal peak (PP, Q(2)), and the third peak (Q(3)), observed in the measured diffraction patterns of disordered materials whose structure contains tetrahedral motifs. It is confirmed that the FSDP (Q(1)) is not a signature of the formation of a network, because an FSDP is observed in tetrahedral molecular liquids. It is found that the PP (Q(2)) reflects orientational correlations of tetrahedra. Q(3), that can be observed in all disordered materials, even in common liquid metals, stems from simple pair correlations. Moreover, information on the topology of disordered materials was revealed by utilizing persistent homology analyses. The persistence diagram of silica (SiO2) glass suggests that the shape of rings in the glass is similar not only to those in the crystalline phase with comparable density (alpha-cristobalite), but also to rings present in crystalline phases with higher density (alpha-quartz and coesite); this is thought to be the signature of disorder. Furthermore, we have succeeded in revealing the differences, in terms of persistent homology, between tetrahedral networks and tetrahedral molecular liquids, and the difference/similarity between liquid and amorphous (glassy) states. Our series of analyses demonstrated that a combination of diffraction data and persistent homology analyses is a useful tool for allowing us to uncover structural features hidden in halo pattern of disordered materials. (C) 2019 The Ceramic Society of Japan. All rights reserved.
• Anomaly of structural relaxation in complex liquid metal of bismuth - Dynamic correlation function of coherent quasi-elastic neutron scattering
  Yukinobu Kawakita; Tatsuya Kikuchi; Yasuhiro Inamura; Shuta Tahara; Kenji Maruyama; Takayasu Hanashima; Mitsutaka Nakamura; Ryoji Kiyanagi; Yasuhiro Yamauchi; Kaori Chiba; Seiko Ohira-Kawamura; Yoshifumi Sakaguchi; Hironori Shimakura; Ryuta Takahashi; Kenji Nakajima
  551, 291, 296, 15 Dec. 2018, © 2017 Elsevier B.V. Liquid Bi has complex structure that a characteristic shoulder structure aside of the first peak exists both in structure factor and pair distribution function. To investigate origin of this complexity from atomic dynamics, we performed quasi-elastic neutron scattering measurements. A new procedure to reduce real-time and real-space functions from the dynamic structure factor obtained in momentum-transfer and energy-transfer space was introduced to prevent truncation errors in Fourier transforms. The reduced intermediate scattering functions and van Hove dynamical correlation functions reveal that the shoulder structure shows characteristic relaxation interpreted as process loosing double-layered structure based on Peierls distortion in liquid Bi. The robustness of the shoulder structure against temperature can be understood by metallic nature of the local structure.
• Structural and Thermal Studies on Racemic PbC4H4O6•2H2O Single Crystal
  T. Fukami; S. Tahara
  Chem. Sci. Int. J., 25, 1, 9, Dec. 2018
• Structural and Thermal Studies on Racemic BaC4H4O6•H2O
  T. Fukami; S. Hiyajyo; S. Tahara
  Chem. Sci. Int. J., 20, 1, 10, Oct. 2017
• Magnetic Properties of Liquid RE-Co (RE = Dy, Er) Alloys
  Satoru Ohno; Hironori Shimakura; Shuta Tahara; Tatsuya Okada
  151, 21 Aug. 2017, The magnetic susceptibilities χ of liquid Dy-Co and Er-Co alloys have a large and negative temperature coefficient, which suggests that the Dy, Er, and Co ions in their liquid alloys are in the magnetic state. However, the temperature dependence of χ in both systems becomes weak near the content of 70 at% Co. It is interesting that the compositional dependence of χ for liquid Dy-Co and Er-Co alloys has a minimum at content of 80 at% Co, respectively. On the Co-rich side, the magnetic susceptibility of liquid Dy-Co and Er-Co alloys obeyed the Curie-Weiss law with regard to their temperature dependence of χ. On the rare earth-rich side, the magnetic susceptibilities of liquid Dy-Co and Er-Co alloys also exhibited Curie behavior with a reasonable value for the effective number of Bohr magnetons. The compositional dependence of χ4f for liquid Dy-Co and Er- Co alloys was extracted by subtracting the corresponding data for liquid La-Co alloys from χ for the liquid Dy-Co and Er-Co alloys, respectively.
• Magnetic Susceptibility of liquid Gd-NM (NM = Cu, Ga, Ge) alloys
  Hironori Shimakura; Shuta Tahara; Tatsuya Okada; Satoru Ohno
  151, 21 Aug. 2017, For rare earth alloys, the indirect interaction of RKKY is at work between rare-earth atoms. Therefore, the magnetism of them depends on the number of conduction electrons and the distance between rare-earth metals. In this work, to reveal the relationship between the number of conduction electrons and magnetic property of rare earth metal alloys, magnetic susceptibility measurements for liquid Gd-NM (NM = Cu, Ga, Ge) was performed by Faraday method. As the results, it was observed that the sign of paramagnetic Curie temperature of Cu-Gd alloys are positive at all composition, while Ga-Gd and Ge-Gd alloys show negative paramagnetic Curie temperature at certain composition. Moreover, it was indicated when the alloy at certain composition shows highest melting temperature, it has the lowest paramagnetic Curie temperature.
• Structure and Ionic Diffusion in Molten NaI, RbI, and NaI-RbI mixture
  Shuta Tahara; Koji Ohara; Hironori Shimakura; Takanori Fukami
  151, 21 Aug. 2017, Static structure factors of molten NaI, RbI, and their mixture of (RbI)0.3(NaI)0.7 are measured up to high-Q region by using the high-energy Xray diffraction technique. Moreover, molecular dynamics (MD) simulations are carried out, and the simulation results well reproduce the diffraction data. The partial structure factors, partial pair distribution functions, and ionic diffusion coefficients calculated by the MD simulations are reported in detail. The mixing effects of cations on the structure and ionic diffusion are also discussed.
• Structural analyses for molten NaNO3 by molecular dynamics simulation
  S. Tahara; H. Toyama; H. Shimakura; T. Fukami
  EPJ Web conf., その他の出版社, Aug. 2017
• Ionic conductivities of molten CuI and CuI-AgI mixtures
  S. Tahara; H. Shimakura; S. Ohno; T. Fukami
  EPJ Web conf., その他の出版社, Aug. 2017
• Crystal Structure and Thermal Properties of Racemic SrC4H6O6・4H2O Single Crystals
  T. Fukami; S. Hiyajyo; S. Tahara; C. Yasuda
  Int. Res. J. Pure & Appl. Chem., その他の出版社, 14, 34299, Jun. 2017
• Thermal Properties and Crystal Structure of BaC4H4O6 Single Crystals
  T. Fukami; S. Hiyajyo; S. Tahara; C. Yasuda
  Int. J. Chem., その他の出版社, 9, 1, Jan. 2017
• Magnetic Property of Liquid Gd-TM (TM = Mn, Fe, Co, Ni) Alloys
  S. Ohno; H. Shimakura; S. Tahara; T. Okada
  J. Phys. Soc. Jpn., その他の出版社, 85, 124715, Nov. 2016
• The structure of molten CuCl: Reverse Monte Carlo modeling with high-energy X-ray diffraction data and molecular dynamics of a polarizable ion model
  Olga Alcaraz; Joaquim Trullas; Shuta Tahara; Yukinobu Kawakita; Shin'ichi Takeda
  145, 9, 94503, Sep. 2016, The results of the structural properties of molten copper chloride are reported from high-energy X-ray diffraction measurements, reverse Monte Carlo modeling method, and molecular dynamics simulations using a polarizable ion model. The simulated X-ray structure factor reproduces all trends observed experimentally, in particular the shoulder at around 1 angstrom(-1) related to intermediate range ordering, as well as the partial copper-copper correlations from the reverse Monte Carlo modeling, which cannot be reproduced by using a simple rigid ion model. It is shown that the shoulder comes from intermediate range copper-copper correlations caused by the polarized chlorides. Published by AIP Publishing.
• Thermal Properties, Crystal Structure, and Phase Transition of Racemic CaC4H4O6·4H2O Single Crystals
  T. Fukami; S. Hiyajyo; S. Tahara; C. Yasuda
  Am. Chem. Sci. J., その他の出版社, 16, 28258, Sep. 2016
• Structural Refinements and Thermal Properties of L(+)-Tartaric, D(–)-Tartaric, and Monohydrate Racemic Tartaric Acid
  T. Fukami; S. Tahara; C. Yasuda; K. Nakasone
  Int. J. Chem., その他の出版社, 8, 9, May 2016
• Crystal Structure and Thermal Properties of SrC4H4O6·4H2O Single Crystals
  T. Fukami; S. Tahara; C. Yasuda; K. Nakasone
  Int. Res. J. Pure & Appl. Chem., その他の出版社, 11, 1, Jan. 2016
• Magnetic Properties of Liquid 3d Transition Metal-Ge Alloys
  Satoru Ohno; Hironori Shimakura; Shuta Tahara; Tatsuya Okada
  84, 7, Jul. 2015, The magnetic susceptibilities (chi) of liquid Ti-Ge and V-Ge alloys show a weak and positive temperature dependence in restricted regions of up to 30 at.% Ti and 40 at.% V, respectively. This suggests that the Ti and V ions in these liquid alloys are in a nonmagnetic state. The chi values of liquid TM-Ge (TM = Fe, Co, Ni) alloys on the Ge-rich side exhibit a similar temperature dependence. The data in the nonmagnetic state were analyzed using the Anderson model. In the nonmagnetic state, we found smooth variations in which both the effective intra-atomic d-d interaction and the density of 3d states at the Fermi level E-F decrease with increasing E-F of liquid TM0.1M0.9 (M = Sn -> Ge -> Si) alloys. Liquid Cr1-cGec with c >= 0.7 and Mn1-cGec with c >= 0.3 obeyed the Curie-Weiss law with regard to the temperature dependence of their chi. The composition dependences of the chi of liquid Cr-Ge and Mn-Ge alloys show maxima at compositions of 50 at.% Cr and 70 at.% Mn, respectively. The magnetic susceptibilities of liquid Fe1-cGec with c <= 0.7, liquid Co1-cGec with c <= 0.3, and liquid Ni1-cGec with c <= 0.1 also exhibited a Curie-Weiss-type behavior. We compared the effective number of Bohr magnetons of liquid TM-Ge alloys with those of liquid TM-Sn and TM-Si alloys at the same TM composition and also investigated the relationship between chi(3d) and E-F for liquid TM0.5M0.5 alloys.
• Intermediate-range chemical ordering of cations in molten RbCl-AgCl
  S. Tahara; Y. Kawakita; H. Shimakura; K. Ohara; T. Fukami; S. Takeda
  143, 4, 44509, Jul. 2015, A first sharp diffraction peak (FSDP) is observed in the X-ray total structure factor of a molten mixture of RbCl-AgCl, while both pure melts of RbCl and AgCl do not exhibit FSDP individually. Molecular dynamics simulations were performed to investigate the origin of the FSDP with the polarizable ion model (PIM). Coexistence of covalent Ag-Cl and ionic Rb-Cl bonds leads the system to evolve intermediate range ordering, which is simulated by introducing the induced polarization in different ways between Ag-Cl with fully polarizable treatment based on Vashishta-Raman potential and Rb-Cl with suppression over-polarization in the nearest neighbor contribution based on Born-Meyer potential. The partial structure factors for both the Ag-Ag and Rb-Rb correlations, SAgAg(Q) and SRbRb(Q), show a positive contribution to the FSDP, while SAgRb(Q) for the Ag-Rb correlation exhibits a negative contribution, indicating that Ag and Rb ions are distributed in an alternating manner within the intermediate-range length scale. The origin of the intermediate-range chemical ordering of cations can be ascribed to the preferred direction of the dipole moments of anions in the PIM. (C) 2015 AIP Publishing LLC.
• Anion Polarization Effects on Static Structure and Ionic Transport in Superionic Melt of RbAg4I5
  Shuta Tahara; Takanori Fukami
  84, 2, 24602, Feb. 2015, The anion polarization effects on the static structure and ionic transport in the superionic melt of RbAg4I5 are investigated by molecular dynamics simulations with the rigid ion model and the polarizable ion model (PIM). The first sharp diffraction peak (FSDP) observed in the experimental static structure factor is reproduced in the case of the PIM, and cation-cation partial structure factors show the characteristic FSDP for Ag-Ag and Rb-Rb correlations and a negative FSDP for the Ag-Rb correlation, indicating that Ag and Rb ions are alternately distributed with an intermediate-range length scale. Ag ions form small clusters of the various sizes, which relates to the density fluctuation and intermediate-range ordering of Ag ions. Rb and the surrounding I ions generate the regions where Ag ions cannot penetrate with the radius of 4-5 angstrom, which is revealed by void analysis by the Voronoi-Delaunay method. The superionic feature remains even in the molten state since the diffusion coefficient of Ag ions is several times larger than that of anions, which is emphasized by introducing anion polarization effects.
• Two low-energy excitations in superionic conductors of RbAg4I5 and KAg4I5
  S. Tahara; Y. Kawakita; M. Nakamura; H. Shimakura; T. Kikuchi; Y. Inamura; S. Ohira-Kawamura; K. Nakajima; T. Sunakawa; T. Fukami
  JPS Conf. Proc., その他の出版社, 8, 31008, 2015
• Magnetic Susceptibilities of Liquid Cr-Au, Mn-Au and Fe-Au Alloys
  S. Ohno; H. Shimakura; S. Tahara; T. Okada
  1673, 20018, 2015, The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr1-cAuc with 0.5 <= c and Mn1-cAuc with 0.3 <= c obeyed the Curie-Weiss law with regard to their dependence of chi on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of chi for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of chi for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of chi(3d) due to 3d electrons for liquid binary TM-M (M= Au, Al, Si, Sb), and investigated the relationship between chi(3d) and E-F in liquid binary TM-M alloys at a composition of 50 at% TM.
• Synthesis, crystal structure, and thermal properties of CaSO4·2H2O single crystals
  T. Fukami; S. Tahara; K. Nakasone; C. Yasuda
  Int. J. Chem., その他の出版社, 7, 12, 2015
• Magnetic Properties of Liquid 3d Transition Metal-Sn Alloys
  Satoru Ohno; Hironori Shimakura; Shuta Tahara; Tatsuya Okada
  84, 1, 14706, Jan. 2015, The magnetic susceptibilities chi of liquid Ti-Sn and V-Sn alloys on the Sn-rich side have only a weak and positive temperature dependence, which suggests that Ti and V ions in the alloys are in the nonmagnetic state. Similarly, the chi values for liquid Co-Sn and Ni-Sn on the Sn-rich side are also in the nonmagnetic state. The data for nonmagnetic states can be analyzed using the Anderson model. Liquid Cr1-cSnc with c >= 0.5 and Mn1-cSnc with c >= 0.1 obey the Curie-Weiss law with regard to the dependence of chi on temperature. The chi for liquid Fe-Sn, Co1-cSnc with c <= 0.5, and Ni1-cSnc with c <= 0.1 also exhibited Curie-Weiss behavior. The compositional dependence of the chi for liquid alloys has a maximum at 50 at.% Cr for Cr-Sn, 70 at.% Mn for Mn-Sn, and 90 at.% Fe for Fe-Sn. In the present work, the compositional dependence of chi(3d) due to 3d electrons was compared for liquid binary transition metal-metal (TM-M; M = Sn, Ge, Si) alloys restricted to the M of tetravalent liquid metals. We found the inverse correlation of the magnitude of chi(3d) with the Fermi level E-F, obtained at a composition of 50 at.% TM for liquid binary TM-M alloys.
• Magnetic Properties of Liquid 3d Transition Metal-Au Alloys
  Satoru Ohno; Shuta Tahara; Tatsuya Okada
  83, 2, 24710, Feb. 2014, In the present study, the magnetic properties of liquid transition metal-Au alloys were investigated as a function of temperature and composition. The magnetic susceptibility chi of liquid Ti-Au and V-Au alloys was found to be almost independent of temperature or to have only a weak positive temperature dependence, which suggests that the Ti and V ions in the alloys are formally in the nonmagnetic state. For Au-rich compositions, chi in the nonmagnetic state was analyzed using the Anderson model. Liquid Cr-1 Au-c(c) with 0.5 <= c and Mn-1 Au-c(c) with 0.3 <= c obeyed the Curie-Weiss law with regard to the dependence of their chi on temperature. It is interesting to note that the composition dependences of the chi values of liquid Cr-Au, Mn-Au, and Fe-Au alloys have maxima at compositions of 50 at.% Cr, 70 at.% Mn, and 85 at.% Fe, respectively. The magnetic susceptibilities of liquid Fe-Au, Co-Au, and Ni-Au alloys obtained in this work also exhibited Curie-Weiss behavior with reasonable values for the effective numbers of Bohr magnetons. The composition dependences of the chi values of liquid Fe-Au and Ni-Au are enhanced gradually with increasing Ni and Fe contents, respectively. In particular, the chi of liquid Co-Au increases rapidly with increasing Co content in Co-rich alloys. This indicates that there is a positive exchange interaction between parallel spins of Co ions. We compared the composition dependences of chi(3d) due to 3d electrons among liquid binary TM-M (M= Au, Al, Si, Sb) alloys, and investigated the relationship between chi(3d) and EF in liquid binary TM-M alloys at a composition of 50 at.% TM.
• Thermal properties and structures of CsHSO4 and CsDSO4 crystals
  T. Fukami; S. Tahara; K. Nakasone
  Int. Res. J. Pure & Appl. Chem., その他の出版社, 4, 621, 2014
• Phase transition and crystal structure of CsHSeO4 and CsDSeO4 crystal
  T. Fukami; S. Tahara; K. Nakasone; M. Seino
  Int. J. Chem., その他の出版社, 5, 3, 1, 2013
• Crystal growth and structure of a new PbHNSO3 crystal
  T. Fukami; M. Seino; K. Nakasone; S. Tahara
  Int. J. Chem., その他の出版社, 5, 1, 1, 2013
• Magnetic Property of Liquid 3d Transition Metal-Sb Alloys
  Satoru Ohno; Shuta Tahara; Tatsuya Okada
  81, 11, 114714, Nov. 2012, Measurements of the magnetic susceptibilities chi of liquid 3d transition metal-Sb alloys were carried out systematically to determine the composition of transition metals where the magnetic-to-nonmagnetic transition occurs. Liquid Ni1-cSbc with c <= 0.11, liquid Co1-cSbc with c <= 0.50, liquid Fe1-cSbc with c <= 0.90, liquid Mn1-cSbc with 0.20 <= c <= 0.91, and liquid Cr1-cSbc with 0.42 <= c <= 0.90 exhibited the Curie-Weiss behavior with a reasonable effective number of Bohr magnetons. The magnetic susceptibilities of other liquid TM-Sb alloys were found to be almost independent of temperature, which suggests that TM ions in their TM-Sb alloys are in the nonmagnetic state. On the Sb-rich side, chi in the nonmagnetic state was studied using the Anderson model. The composition dependence of chi for liquid Ni-Sb and Fe-Sb increases gradually with increasing Ni and Fe compositions, respectively. Particularly, chi for liquid Co-Sb increases rapidly on the Co-rich side. This suggests that there is a strong interatomic exchange interaction between parallel spins of Co ions. The composition dependences of chi for liquid Mn-Sb and Cr-Sb alloys show maxima at compositions of 70 at.% Mn and 50 at.% Cr, respectively.
• Fluctuations in medium-range structure of Bi-based metallic liquid alloys
  H. Ueno; Y. Kawakita; K. Ohara; S. Tahara; S. Kohara; M. Itou; S. Takeda
  340, 12081, 2012, Liquid structure of Bi50Zn50, which is situated at around the Bi-rich end of miscibility gap in Bi-Zn system, has been investigated by neutron and x-ray diffraction experiments and following analysis using reverse Monte Carlo (RMC) structural modelling. Among the partial correlations calculated from the structural model obtained by RMC, the Zn-Zn partial has a large temperature variation. It is found that there are medium-range fluctuations in Zn distribution which have a scale of 10 angstrom.
• Transport Properties of Molten CuCl-Cu2Se Mixtures
  Satoru Ohno; Shuta Tahara; Tatsuya Okada
  80, 11, 114709, Nov. 2011, The electrical conductivity, sigma, and the thermoelectric power, S, have been measured for molten CuCl-Cu2Se mixtures as a function of composition and temperature. The electrical conductivity of their mixtures decreases rapidly with the addition of CuCl to liquid Cu2Se. The thermoelectric power of molten CuCl-Cu2Se mixtures shows a steady increase with increasing amount of CuCl. The experimental results suggest that the dominant transport process in the molten CuCl-Cu2Se mixtures changes from electronic to ionic conduction. The composition dependence of sigma and S was analyzed by using the fundamental equation of electrical current densities due to the electrons and the ions. According to this analysis, the conductivity gap increases gradually upon the addition of CuCl to liquid Cu2Se, and the conductivity gap is about 0.68 eV for a molten (CuCl)(0.3)(Cu2Se)(0.7) mixture.
• Medium-range correlation of Ag ions in superionic melts of Ag2Se and AgI by reverse Monte Carlo structural modelling-connectivity and void distribution
  Shuta Tahara; Hiroki Ueno; Koji Ohara; Yukinobu Kawakita; Shinji Kohara; Satoru Ohno; Shin'ichi Takeda
  J. Phys.: Condence. Matter, その他の出版社, 23, 23, 235102, Jun. 2011, High-energy x-ray diffraction measurements on molten Ag2Se were performed. Partial structure factors and radial distribution functions were deduced by reverse Monte Carlo (RMC) structural modelling on the basis of our new x-ray and earlier published neutron diffraction data. These partial functions were compared with those of molten AgI. Both AgI and Ag2Se have a superionic solid phase prior to melting. New RMC structural modelling for molten AgI was performed to revise our previous model with a bond-angle restriction to reduce the number of unphysical Ag triangles. The refined model of molten AgI revealed that isolated unbranched chains formed by Ag ions are the cause of the medium-range order of Ag. In contrast with molten AgI, molten Ag2Se has 'cage-like' structures with approximately seven Ag ions surrounding a Se ion. Connectivity analysis revealed that most of the Ag ions in molten Ag2Se are located within 2.9 angstrom of each other and only small voids are found, which is in contrast to the wide distribution of Ag-void radii in molten AgI. It is conjectured that the collective motion of Ag ions through small voids is required to realize the well-known fast diffusion of Ag ions in molten Ag2Se, which is comparable to that in molten AgI.
• Electrical properties of molten CuCl-Cu2Se mixtures
  S. Ohno; K. Ishida; S. Tahara; T. Okada
  15, 1003, 2011, The electrical conductivity, sigma, and the thermoelectric power, S, have been measured for molten CuCl-Cu2Se mixtures as a function of composition and temperature. The electrical conductivity of their mixtures decreases rapidly with the addition of CuCl to liquid Cu2Se. The thermoelectric power of molten CuCl-Cu2Se mixtures shows a steady increase with increasing the composition of CuCl. The experimental results suggest that the dominant transport process in the molten CuCl-Cu2Se mixtures changes from electronic to ionic conduction. The composition dependence of sigma and S was analyzed by using the fundamental equation of electrical current densities due to the electrons and the ions. According to this analysis, the conductivity gap increases gradually on the addition of CuCl to liquid Cu2Se and the conductivity gap is about 0.68 eV for molten (CuCl)(0.3)(Cu2Se)(0.7) mixture.
• Concentration Effects of Silver Ions on Ionic Conductivity of Molten Silver Halides
  S. Tahara; S. Ohno; T. Okada; Y. Kawakita; S. Takeda
  The European Physical Journal Web of Conferences, その他の出版社, 15, 2005, 2011
• Electrical Properties of Molten CuCl-Cu2Te Mixtures
  Satoru Ohno; Shuta Tahara; Tatsuya Okada
  79, 11, 114702, Nov. 2010, The electrical conductivity sigma and the thermoelectric power S of molten (CuCl)(1-c)(Cu2Te)(c) mixtures are measured as a function of composition and temperature. The electrical conductivity of the mixtures decreases rapidly with the addition of CuCl to liquid Cu2Te. The thermoelectric power of molten (CuCl)(1-c)(Cu2Te)(c) mixtures shows a smooth increase with increasing composition of CuCl. The experimental results suggest that the dominant transport process in the molten (CuCl)(1-c)(Cu2Te)(c) mixtures changes from electronic conduction to ionic conduction. The composition dependences of sigma and S were analyzed using the fundamental equation of electrical current densities due to electrons and ions. According to this analysis, the conductivity gap increases gradually upon the addition of CuCl to liquid Cu2Te and the conductivity gap is about 0.55 eV for molten (CuCl)(0.4)(Cu2Te)(0.6) mixture.
• Concentration Effects of Silver Ions on Forming the Cooperative Conducting Path in Superionic Melts
  Shuta TAHARA; Hiroki UENO; Koji OHARA; Yukinobu KAWAKITA; Shin'ichi TAKEDA; Shinji KOHARA; Satoru OHNO
  J. Phys. Soc. Jpn. Suppl. A, その他の出版社, 79, 133, 2010
• Partial structures in molten AgBr
  Hiroki Ueno; Shuta Tahara; Yukinobu Kawakita; Shinji Kohara; Shin'ichi Takeda
  600, 1, 322, 324, Feb. 2009, The structure of molten AgBr has been studied by means of neutron and X-ray diffractions with the aid of structural modeling. It is confirmed that the Ag-Ag correlation has a small but well-defined first peak in the partial pair distribution function whose tail penetrates into the Ag-Br nearest neighbor distribution. This feature on the Ag-Ag correlation is intermediate between that of molten AgCl (non-superionic melt) and that of molten Agl (superionic melt). The analysis of Br-Ag-Br bond angle reveals that molten AgBr preserves a rocksalt type local ordering in the solid phase, suggesting that molten AgBr is clarified as non-superionic melt like molten AgCl. (C) 2008 Elsevier B.V. All rights reserved.
• Magnetic Properties of Liquid 3d Transition Metal-Al Alloys
  Shuta TAHARA; Satoru OHNO; Tatsuya OKADA
  J. Phys. Soc. Jpn., その他の出版社, 78, 74702, 2009
• Structure of eutectic alloys of Au with Si and Ge
  S. Takeda; H. Fujii; Y. Kawakita; S. Tahara; S. Nakashima; S. Kohara; M. Itou
  452, 1, 149, 153, Mar. 2008, Au-Si and Au-Ge alloy systems have a deep eutectic point in the Au-rich concentration region where the melting point falls down to 633 K. In order to investigate the liquid structure in relation to the glass-forming tendency of these alloys, high-energy X-ray diffraction measurements have been carried out at the eutectic composition and at compositions with excess amounts of An or IVb element. The nearest neighbor correlations in the eutectic liquids are intense and sharp in the pair distribution function and exhibit a rather small temperature dependence in comparison with those alloys of other than the eutectic composition. Structural models for these liquid alloys are proposed with the aid of reverse Monte Carlo simulation. The reproduced atomic arrangements around the eutectic region exhibit a substitutional-type structure where the dense random packing of Au atoms is preserved and Si or Ge atoms occupy the Au-sites at random. (c) 2007 Published by Elsevier B.V.
• Structure of Eutectic Liquids Between Noble Metal- IVB Elements
  S. Takeda; H. Fujii; Y. Kawakita; S. Tahara; S.Nakashima; S. Kohara; M. Itou
  J. Alloys and Compounds, 452, 149, 153, 2008
• Static structure of superionic conducting glass of Ag-Ge-Se system
  R. Suenaga; Y. Kawakita; S. Nakashima; S. Tahara; S. Kohara; S. Takeda
  98, 12021, 2008, Superionic conducting glasses are the important materials as solid electrolytes. Amorphous Ag-Ge-Se system is well known to exhibit the superionic conducting behavior where silver ions easily migrate into the mixed structure of Ag2Se and Ge-Se chalcogenide glass. It will be good material to study how the superionic conducting region distributes in the glassy network, and whether the conducting paths extends to the entire of the material, or the localized and limited area in an isolated region. In this paper, we will present the results of the static structure of Ag-Ge-Se system by high-energy X-ray diffraction measurements.
• Comparison of partial structures of melts of superionic AgI and CuI and non-superionic AgCl
  Yukinobu Kawakita; Shuta Tahara; Hiroyuki Fujii; Shinji Kohara; Shin'ichi Takeda
  19, 33, 335201, Aug. 2007, Neutron and high-energy x-ray diffraction analyses of molten AgI have been performed and the partial structures are discussed in detail with the aid of the structural modelling procedure of the reverse Monte Carlo ( RMC) technique by comparison with those of molten CuI and AgCl. It is well known that AgI and CuI have a superionic solid phase below the melting point, in which the cations favour a tetrahedral configuration, while solid AgCl has a rock-salt structure with an octahedral environment around both Ag and Cl atoms. Even in the molten states, there is a significant difference between superionic and nonsuperionic melts. The cation is located on the triangular plain formed by three iodine ions in molten AgCl and CuI, while molten AgCl favours a 90 degrees. Cl-Ag Cl bond angle, which is understood to maintain a similar local environment to that in the solid state. The atomic configurations of the RMC model suggest that the cation distributions in superionic melts of CuI and AgI exhibit large fluctuations, while Ag ions in the non-superionic melts of AgCl are distributed much more uniformly.
• Static and dynamic structures of liquid GeTe mixtures
  Yukinobu Kawakita; Yasuhiko Kato; Shuta Tahara; Hiroyuki Fujii; Shin'ichi Takeda; Kenji Maruyama
  353, 18-21, 1999, 2003, Jun. 2007, Neutron diffraction measurements of the liquid Ge-Te system and quasi- and inelastic neutron scattering experiments of the eutectic liquid Ge15Te85 were performed in the temperature range from 400 to 560 degrees C. The large temperature dependence of the static structure for liquid Ge15Te85 is reconfirmed; however it is found that the compositional dependence obtained at around 80 degrees C above the liquidus curve is rather small. The dynamic structure factors of liquid Ge15Te85 in the Q-region from 0.2 to 2.6 angstrom(-1) show a normal temperature dependence. From the vibrational density of states, it is found that the Te-Te covalent bond persists in liquid Ge15Te85; however a bending mode was not assigned clearly. (c) 2007 Elsevier B.V. All rights reserved.
• Structural properties of liquid Au-Si and Au-Ge alloys with deep eutectic region
  Hiroyuki Fujii; Shuta Tahara; Yasuhiko Kato; Shinji Kohara; Masayoshi Itou; Yukinobu Kawakita; Shin'ichi Takeda
  353, 18-21, 2094, 2098, Jun. 2007, Au-Si and Au-Ge alloys have a deep eutectic region around 19 at.% Si and 28 at.% Ge, respectively. The metallic glass was prepared by quenching around 25 at.% Si near the eutectic composition for the Au-Si alloys [2] which has stimulated many researchers to study on the structural properties of such liquid alloys. However their results were different from each other, which seems due to the experimental difficulties from heavy absorption of both X-ray and neutron beams by Au atom in diffraction experiments. X-ray diffraction measurements have been carried out for liquid Au-Si and Au-Ge alloys around the eutectic region by the transmission method using high-energy X-rays to investigate the atomic arrangements in the liquid state. From the temperature dependence of the observed structure factors, the partial pair correlation and the detailed atomic arrangements will be discussed by Reverse Monte Carlo analysis. The produced atomic arrangements around the eutectic region suggest a substitutional structure and also an increase in liquid density with decreasing temperature. (c) 2007 Elsevier B.V. All rights reserved.
• Structure of the molten silver chloride
  Shuta Tahara; Hiroyuki Fujii; Yukinobu Kawakita; Shinji Kohara; Yukinobu Yokota; Shin'ichi Takeda
  353, 18-21, 1994, 1998, Jun. 2007, The structure of molten AgCl has been studied by neutron and X-ray diffractions. Significant differences in the neutron and X-ray total structure factors have been observed, reflecting different contributions of three partial structures Ag-Ag, Ag-Cl and Cl-Cl. By means of the reversed Monte Calro (RMC) structural modeling and analysis, partial structures have been calculated and then compared with the earlier work [J.Y. Derrien and Dupuy, J. Phys. Chem. Liq, 5 (1976) 71]. The results show that Cl-Cl correlations are similar to those for a close packed structure. Ag-Ag correlations are gas-like and the local structure of unlike pairs is similar to those for a rock salt type structure with vacancy sites. (c) 2007 Elsevier B.V. All rights reserved.
• Structure and electron-ion correlation in liquid Mg
  Shuta Tahara; Hiroyuki Fujii; Yukinobu Yokota; Yukinobu Kawakita; Shinji Kohara; Shin'ichi Takeda
  385, 219, 221, Nov. 2006, For liquid Mg at 700 degrees C, structure factors were obtained from both neutron and X-ray diffraction measurements. The bond angle and coordination number distributions were derived from the reverse Monte Carlo analysis. By a combination of both structure factors, charge density function and electron-ion partial structure factor were deduced. (c) 2006 Elsevier B.V. All rights reserved.

Conference Activities & Talks

• Sep. 2024
• Sep. 2024
• Sep. 2024
• 04 Dec. 2023
• 04 Dec. 2023
• Sep. 2022
• Mar. 2022
• Sep. 2021
• Aug. 2021
• Jan. 2021
• Sep. 2020
• Nov. 2019
• Nov. 2019
• Oct. 2019
• Oct. 2019
• Oct. 2019
• Sep. 2019
• Mode Distribution Analysis for Superionic Melt of CuI by Coherent Quasielastic Neutron Scattering
  The 3rd J-PARC Symposium, Sep. 2019
• Sep. 2019
• Sep. 2019
• May 2019
• Mar. 2019
• Mar. 2019
• Mar. 2019
• Structure of high-temperature liquid oxides revealed by quantum beam diffraction measurements, thermophysical properties measurements and computer simulations
  Feb. 2019
• Feb. 2019
• Network modification in binary vanadium phosphate glass revealed by data driven structure modelling
  Jan. 2019
• Synergic collaboration of quantum beam measurements, modelling, and mathematics to unravel liquid matter: towards a collaboration with microgravity in space
  Jan. 2019
• Topological order in amorphous InGaZnO4
  3rd MI2I All researchers meeting (NIMS), Jan. 2019
• Dec. 2018
• Dec. 2018
• Structure of liquid Er2O3 revealed by synchrotron X-ray diffraction measurements, thermophysical properties measurements, and reverse Monte Carlo – molecular dynamics simulations
  35th International Korea-Japan Seminar on Ceramics, Nov. 2018
• Oct. 2018
• Structure of high-temperature liquid oxides revealed by quantum beam diffraction measurements, themophysical properties measurements and advanced computer simulations
  International Union of Materials Research Society – International Conference in Asia 2018, Oct. 2018
• Sep. 2018
• Sep. 2018
• Sep. 2018
• Jul. 2018
• Jun. 2018
• Mar. 2018
• Mar. 2018
• Dec. 2017
• Dec. 2017
• Nov. 2017
• Nov. 2017
• Oct. 2017
• Sep. 2017
• Jul. 2017
• Mar. 2017
• Mar. 2017
• Mar. 2017
• Jan. 2017
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Misc

• 33, 3, 7, 201803
• 20, 2017

Other Research Activities

Awards & Honors

• The Ceramic Society of Japan, Award of the Outstanding Papers Published in the JCS-Japana in 2019, Understanding diffraction patterns of glassy, liquid and amorphous materials via persistent homology analyses, Y. Onodera;S. Kohara;S. Tahara;A. Masuno;H. Inoue;M. Shiga;A. Hirata;K. Tsuchiya;Y. Hiraoka;I. Obayashi;K. Ohara;A. Mizuno;O. Sakata
• University of the Ryukyus, Professor of The Year
• Physical society of Japan, Young Scientist Award of the Physical Society of Japan
• The 3rd International Conference on Physics of Solide State Ionics, Poster Award (The 3rd International Conference on Physics of Solide State Ionics)

Research Grants & Projects

• 202204, 202603
• 2016, 2018
• 2016, 2018
• 2012, 2014
• Japan Society for the Promotion of Science
  Grants-in-Aid for Scientific Research
  Grant-in-Aid for Scientific Research (C), Formation Mechanism of high-order structure and conduction channel in superionic glasses, 2010, 2012, 22540331, To appearance of superionic behavior in Ag- or Cu-related materials, collective diffusion of cations in molten state plays an important role. In this study, we investigated formation mechanism of higher-order structures and conduction channels in superionic glasses from the viewpoints of static and dynamic structures of their melts. It is found that the higher-order structure in the molten state of AgCl, which shows no superionic behavior at ambient pressure, appears when optimum number density of Ag is realized by mixing RbCl.
• 2011
• 2009