Faculty Profiles - YOKOI Tatsuya

Papers - YOKOI Tatsuya

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Accurate prediction of grain boundary structures and energetics in CdTe: a machine-learning potential approach

Yokoi Tatsuya, Adachi Kosuke, Iwase Sayuri, Matsunaga Katsuyuki

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 24 ( 3 ) page： 1620 - 1629 2022.1

Language：Japanese Publisher：Physical Chemistry Chemical Physics

To accurately predict grain boundary (GB) atomic structures and their energetics in CdTe, the present study constructs an artificial-neural-network (ANN) interatomic potential. To cover a wide range of atomic environments, large amounts of density functional theory (DFT) data are used as a training dataset including point defects, surfaces and GBs. Structural relaxation combined with the trained ANN potential is applied to symmetric tilt and twist GBs, many of which are not included in the training dataset. The relative stability of the relaxed structures and their GB energies are then evaluated with the DFT level. The ANN potential is found to accurately predict low-energy structures and their energetics with reasonable accuracy with respect to DFT results, while conventional empirical potentials critically fail to find low-energy structures. The present study also provides a way to further improve the transferability of the ANN potential to more complicated GBs, using only low-Σ GBs as training datasets. Such improvement will offer a way to accurately predict atomic structures of general GBs within practical computational cost. This journal is

DOI： 10.1039/d1cp04329c

Web of Science

Scopus

PubMed

Effect of La vacancies on the oxide-ion conduction in lanthanum silicate apatites

Ogura Yusuke, Yokoi Tatsuya, Fujii Kotaro, Yashima Masatomo, Matsunaga Katsuyuki

SOLID STATE IONICS Vol. 373 2021.12

Grain-size dependence and anisotropy of nanoscale thermal transport in MgO

Fujii Susumu, Funai Kohei, Yokoi Tatsuya, Yoshiya Masato

APPLIED PHYSICS LETTERS Vol. 119 ( 23 ) 2021.12

Language：Japanese Publisher：Applied Physics Letters

Controlling thermal conductivity in nanocrystalline materials is of great interest in various fields such as thermoelectrics. However, its reduction mechanism has not been fully given due to the difficulty to assess local thermal conduction at grain boundaries (GBs) and grain interiors. Here, we calculated spatially decomposed thermal conductivities across and along MgO symmetric GBs using perturbed molecular dynamics, varying the GB separation from 2.1 to 20.0 nm. This reveals the different length scale of GB scattering for two directions: over hundreds of nanometers across GBs while within a few nanometers along GBs. Numerical analyses based on the spatially decomposed thermal conductivities demonstrate that the former is dominant upon suppressing thermal conductivity in polycrystalline materials, whereas the latter has a non-negligible impact in nanocrystalline materials because of a large reduction of intragrain thermal conductivity along GBs. These insights provide the exact mechanisms of heat transport in nanocrystalline materials toward more precise control of thermal conductivity.

DOI： 10.1063/5.0075854

Web of Science

Scopus

Preferential growth mode of large-sized vacancy clusters in silicon: A neural-network potential and first-principles study Invited Reviewed

T. Ushiro, T. Yokoi, Y. Noda, E. Kamiyama, M. Ohbitsu, H. Nagakura, K. Sueoka, K. Matsunaga

Journal of Physical Chemistry C Vol. 125 ( 48 ) page： 26869 - 26882 2021.11

Differential clustering of self-interstitials during Si crystal growth

Kamiyama Eiji, Yokoi Tatsuya, Noda Yusuke, Sueoka Koji

JOURNAL OF CRYSTAL GROWTH Vol. 574 2021.11

First-principles based theoretical calculations of atomic structures of hydroxyapatite surfaces and their charge states in contact with aqueous solutions

Saito T., Yokoi T., Nakamura A., Matsunaga K.

RSC ADVANCES Vol. 11 ( 54 ) page： 34004 - 34014 2021.10

Segregation mechanism of arsenic dopants at grain boundaries in silicon

Yutaka Ohno, Tatsuya Yokoi, Yasuo Shimizu, Jie Ren, Koji Inoue, Yasuyoshi Nagai, Kentaro Kutsukake, Kozo Fujiwara, Atsutomo Nakamura, Katsuyuki Matsunaga, Hideto Yoshida

Science and Technology of Advanced Materials: Methods 2021.8

Direct imaging of atomistic grain boundary migration

Wei Jiake, Feng Bin, Ishikawa Ryo, Yokoi Tatsuya, Matsunaga Katsuyuki, Shibata Naoya, Ikuhara Yuichi

NATURE MATERIALS Vol. 20 ( 7 ) page： 951 - + 2021.7

An origin of excess vibrational entropies at grain boundaries in Al, Si and MgO: a first-principles analysis with lattice dynamics

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

PHYSICAL CHEMISTRY CHEMICAL PHYSICS Vol. 23 ( 16 ) page： 10118 - 10129 2021.4

Photoindentation: A New Route to Understanding Dislocation Behavior in Light

Nakamura Atsutomo, Fang Xufei, Matsubara Ayaka, Tochigi Eita, Oshima Yu, Saito Tatsushi, Yokoi Tatsuya, Ikuhara Yuichi, Matsunaga Katsuyuki

NANO LETTERS Vol. 21 ( 5 ) page： 1962 - 1967 2021.3

Crystal and Electronic Structures of MoSi2-Type CrGe2 Synthesized under High Pressure

Sasaki Takuya, Kanie Kota, Yokoi Tatsuya, Niwa Ken, Gaida Nico Alexander, Matsunaga Katsuyuki, Hasegawa Masashi

INORGANIC CHEMISTRY Vol. 60 ( 3 ) page： 1767 - 1772 2021.2

Stable and metastable structures and their energetics of asymmetric tilt grain boundaries in MgO: a simulated annealing approach

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

JOURNAL OF MATERIALS SCIENCE Vol. 56 ( 4 ) page： 3183 - 3196 2021.2

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

Ogura Yusuke, Yokoi Tatsuya, Toyoura Kazuaki, Matsunaga Katsuyuki

SOLID STATE IONICS Vol. 355 2020.11

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 Vol. 103 ( 9 ) page： 5354 - 5364 2020.9

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

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

ACTA MATERIALIA Vol. 195 page： 690 - 697 2020.8

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

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

Acta Materialia Vol. 195 page： 645 - 653 2020.8

Language：Japanese Publishing type：Research paper (scientific journal)

© 2020 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

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

NATURE COMMUNICATIONS Vol. 11 ( 1 ) 2020.4

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 Vol. 20 ( 4 ) page： 2530 - 2536 2020.4

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

Fujii Susumu, Ioki Arata, Yokoi Tatsuya, Yoshiya Masato

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY Vol. 40 ( 3 ) page： 780 - 788 2020.3

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 Vol. 4 ( 2 ) 2020.2

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Papers - YOKOI Tatsuya