研究者詳細 - 横井　達矢

論文 - 横井　達矢

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First-principles analysis of oxide-ion conduction mechanism in neodymium silicate

Ogura Yusuke, Yokoi Tatsuya, Toyoura Kazuaki, Matsunaga Katsuyuki

SOLID STATE IONICS 355 巻 2020年11月

Formation energies and site preference of substitutional divalent cations in carbonated apatite

Saito Tatsushi, Yokoi Tatsuya, Nakamura Atsutomo, Matsunaga Katsuyuki

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 103 巻 ( 9 ) 頁： 5354 - 5364 2020年9月

Room-temperature creep deformation of cubic ZnS crystals under controlled light conditions Open Access

Oshima Yu, Nakamura Atsutomo, Lagerlof K. Peter D., Yokoi Tatsuya, Matsunaga Katsuyuki

ACTA MATERIALIA 195 巻頁： 690 - 697 2020年8月

Carrier-trapping induced reconstruction of partial-dislocation cores responsible for light-illumination controlled plasticity in an inorganic semiconductor Open Access

Matsunaga Katsuyuki, Hoshino Sena, Ukita Masaya, Oshima Yu, Yokoi Tatsuya, Nakamura Atsutomo

ACTA MATERIALIA 195 巻頁： 645 - 653 2020年8月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Acta Materialia

Inorganic semiconductors show interesting mechanical behavior in response to their surrounding lighting environments. In fact, we recently found out that zinc sulfide (ZnS) shows the light-illumination controlled plasticity at room temperature. However, its mechanism is poorly understood. Here we report systematic density functional theory results of electronic and atomic structures of glide partial dislocations in ZnS. We have revealed that partial dislocations in ZnS have excess electrostatic fields localized around their cores and can trap electrons or holes, depending on excess ionic species at the cores. Such carrier-dislocation interactions can induce energetically more stable bond reconstruction at their cores, as compared with the case before carrier trapping. Reconstructed bonds at the dislocation cores should be broken upon dislocation glide, and thus can restrict the dislocation motion significantly. Such reduced dislocation motion due to core reconstruction should give rise to increased plastic deformation stresses, namely, hardening of the materials under light illumination. The present results provide a critical understanding of the experimentally observed light-illumination controlled plasticity in ZnS at the electronic level, which is opposed to previously reported plasticity and dislocation motion in other elemental and III-V semiconductors.

DOI： 10.1016/j.actamat.2020.06.010

Web of Science

Scopus

Quantitative prediction of grain boundary thermal conductivities from local atomic environments Open Access

Fujii Susumu, Yokoi Tatsuya, Fisher Craig A. J., Moriwake Hiroki, Yoshiya Masato

NATURE COMMUNICATIONS 11 巻 ( 1 ) 2020年4月

Direct Measurement of Electronic Band Structures at Oxide Grain Boundaries

Wei Jiake, Ogawa Takafumi, Feng Bin, Yokoi Tatsuya, Ishikawa Ryo, Kuwabara Akihide, Matsunaga Katsuyuki, Shibata Naoya, Ikuhara Yuichi

NANO LETTERS 20 巻 ( 4 ) 頁： 2530 - 2536 2020年4月

Role of phonons on phase stabilization of RE2Si2O7 over wide temperature range (RE = Yb, Gd) Open Access

Fujii Susumu, Ioki Arata, Yokoi Tatsuya, Yoshiya Masato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 40 巻 ( 3 ) 頁： 780 - 788 2020年3月

Dependence of excess vibrational entropies on grain boundary structures in MgO: A first-principles lattice dynamics

Yokoi T., Arakawa Y., Ikawa K., Nakamura A., Matsunaga K.

PHYSICAL REVIEW MATERIALS 4 巻 ( 2 ) 2020年2月

Neural-network interatomic potential for grain boundary structures and their energetics in silicon

Yokoi T., Noda Y., Nakamura A., Matsunaga K.

PHYSICAL REVIEW MATERIALS 4 巻 ( 1 ) 2020年1月

Atomistic mechanisms of thermal transport across symmetric tilt grain boundaries in MgO Open Access

Fujii Susumu, Yokoi Tatsuya, Yoshiya Masato

ACTA MATERIALIA 171 巻頁： 154 - 162 2019年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Acta Materialia

Grain boundaries often have a decisive effect on the macroscopic properties of polycrystalline materials, but the wide variety of their atomic structures, interfacial lengths, and compositions makes them difficult to characterize all-encompassingly. An indispensable example in which an understanding of the relationship between grain boundary structures and properties would greatly facilitate development of superior materials is thermal transport, especially with respect to microstructure evolution, thermoelectrics and thermal barrier coatings. To contribute to a more comprehensive understanding, we performed a systematic study of lattice thermal conduction across a wide range of symmetric tilt grain boundaries in MgO using perturbed molecular dynamics. It was found that thermal conductivities vary significantly with grain boundary structure but are strongly correlated with excess volume, which is a measure of the number density of atoms in the vicinity of the grain boundary planes. Real-space analysis revealed that dislocation densities determine the phonon transport paths and thermal conductivity in low-angle boundaries whereas it is the amount of open volume rather than the shape of structural units in high-angle boundaries that determine thermal conductivity. We also found that low-angle boundaries mainly reduce phonon transports at low frequencies whereas high-angle boundaries also reduce it at intermediate and high frequencies effectively, regardless of the shape of structural units. These insights are expected to be applicable to other close-packed oxide systems, and should aid the design of next-generation thermal materials through tailoring of grain boundaries.

DOI： 10.1016/j.actamat.2019.04.009

Web of Science

Scopus

Theoretical Calculations of Characters and Stability of Glide Dislocations in Zinc Sulfide Open Access

Ukita Masaya, Nagahara Ryota, Oshima Yu, Nakamura Atsutomo, Yokoi Tatsuya, Matsunaga Katsuyuki

MATERIALS TRANSACTIONS 60 巻 ( 1 ) 頁： 99 - 104 2019年

Oxide-ion conduction via interstitials in scheelite-type LaNbO4: a first-principles study

Toyoura Kazuaki, Sakakibara Yusuke, Yokoi Tatsuya, Nakamura Atsutomo, Matsunaga Katsuyuki

JOURNAL OF MATERIALS CHEMISTRY A 6 巻 ( 25 ) 頁： 12004-12011 2018年7月

Interaction of sodium atoms with stacking faults in silicon with different Fermi levels Open Access

Ohno Yutaka, Morito Haruhiko, Kutsukake Kentaro, Yonenaga Ichiro, Yokoi Tatsuya, Nakamura Atsutomo, Matsunaga Katsuyuki

APPLIED PHYSICS EXPRESS 11 巻 ( 6 ) 2018年6月

Atomistic simulations of grain boundary transformation under high pressures in MgO 査読有り Open Access

Yokoi T., Yoshiya M.

PHYSICA B-CONDENSED MATTER 532 巻頁： 2 - 8 2018年3月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica B: Condensed Matter

This study focuses on transformation of grain boundary (GB) structures under high pressures up to 60 GPa by using a simulated annealing technique with molecular dynamics and lattice statics calculations for various symmetric tilt GBs (STGBs) of MgO. It is found that except for the Σ3(111)/[11¯0] that is a rather stable GB, all the STGBs studied transform into a metastable structure more than once at threshold pressures. In addition, the GBs with an open-core structure and small tilt angle are found to be more “flexible” to transform into different structures than the GBs with a dense structure. For polycrystalline MgO, therefore, GBs may also exhibit GB transformation under high pressures and flexible GBs may govern overall transformation and deformation. These findings also suggest that polycrystals sintered at high pressures consist of more pressure-resistant GBs than those at normal pressures.

DOI： 10.1016/j.physb.2017.03.014

Web of Science

Scopus

Structure of the Basal Edge Dislocation in ZnO Open Access

Nakamura Atsutomo, Tochigi Eita, Nagahara Ryota, Furushima Yuho, Oshima Yu, Ikuhara Yuichi, Yokoi Tatsuya, Matsunaga Katsuyuki

CRYSTALS 8 巻 ( 3 ) 2018年3月

Electronic and atomic structures of edge and screw dislocations in rock salt structured ionic crystals

Ukita Masaya, Nakamura Atsutomo, Yokoi Tatsuya, Matsunaga Katsuyuki

PHILOSOPHICAL MAGAZINE 98 巻 ( 24 ) 頁： 2189-2204 2018年

Atomically ordered solute segregation behavior in an oxide grain boundary 査読有り Open Access

B. Feng, T. Yokoi, A. Kumamoto, M. Yoshiya, Y. Ikuhara, N. Shibata

Nature Communications 2016年3月

Atomistic analyses of Competition between Site-Selective Segregation and Association of Point Defects at Grain Boundary in Y₂O₃-doped ZrO₂ 査読有り Open Access

T. Yokoi, M. Yoshiya, H. Yasuda

Material Transaction 2015年8月

On modeling of grain boundary segregation in aliovalent cation doped ZrO₂: Critical factors in site-selective point defect occupancy 査読有り

T. Yokoi, M. Yoshiya, H. Yasuda

Scripta Materialia 2015年3月

Nonrnadom Point Defect Configurations and Driving Force Transitions for Grain Boundary Segregation in Trivalent Cation Doped ZrO₂ 査読有り

T. Yokoi, M. Yoshiya, H. Yasuda

Langmuir 2014年11月

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