Faculty Profiles - YOKOI Tatsuya

Papers - YOKOI Tatsuya

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

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

PHYSICAL REVIEW MATERIALS Vol. 4 ( 1 ) 2020.1

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

Susumu Fujii, Tatsuya Yokoi, Masato Yoshiya

Acta Materialia Vol. 171 page： 154 - 162 2019.6

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

© 2019 Acta Materialia Inc. 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

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

MATERIALS TRANSACTIONS Vol. 60 ( 1 ) page： 99 - 104 2019

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 Vol. 6 ( 25 ) page： 12004-12011 2018.7

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

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

APPLIED PHYSICS EXPRESS Vol. 11 ( 6 ) 2018.6

Atomistic simulations of grain boundary transformation under high pressures in MgO Reviewed

T. Yokoi, M. Yoshiya

Physica B: Condensed Matter Vol. 532 page： 2 - 8 2018.3

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

© 2017 Elsevier B.V. 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

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

CRYSTALS Vol. 8 ( 3 ) 2018.3

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 Vol. 98 ( 24 ) page： 2189-2204 2018

Atomically ordered solute segregation behavior in an oxide grain boundary Reviewed

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

Nature Communications 2016.3

Atomistic analyses of Competition between Site-Selective Segregation and Association of Point Defects at Grain Boundary in Y₂O₃-doped ZrO₂ Reviewed

T. Yokoi, M. Yoshiya, H. Yasuda

Material Transaction 2015.8

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

T. Yokoi, M. Yoshiya, H. Yasuda

Scripta Materialia 2015.3

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

T. Yokoi, M. Yoshiya, H. Yasuda

Langmuir 2014.11

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Papers - YOKOI Tatsuya