Machine learning molecular dynamics simulations for evaluation of high-temperature properties of nuclear fuel materials

Kobayashi, Keita; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Okumura, Masahiko

Materia, 62(3), p.175 - 181, 2023/03

https://doi.org/10.2320/materia.62.175

no abstracts in English

Long-timescale transformations of self-interstitial atom clusters of Cu using the SEAKMC method; The Effect of setting an activation energy threshold for saddle point searches

Hayakawa, Sho*; Yamamoto, Yojiro*; Okita, Taira*; Itakura, Mitsuhiro; Suzuki, Katsuyuki*

Computational Materials Science, 218, p.111987_1 - 111987_10, 2023/02

https://doi.org/10.1016/j.commatsci.2022.111987

Molecular dynamics simulations to quantify the interaction of a rigid and impenetrable precipitate with an edge dislocation in Cu

Tsugawa, Kiyoto*; Hayakawa, Sho*; Iwase, Yuki*; Okita, Taira*; Suzuki, Katsuyuki*; Itakura, Mitsuhiro; Aichi, Masaatsu*

Computational Materials Science, 210, p.111450_1 - 111450_9, 2022/07

https://doi.org/10.1016/j.commatsci.2022.111450

Machine learning molecular dynamics simulations toward exploration of high-temperature properties of nuclear fuel materials; Case study of thorium dioxide

Kobayashi, Keita; Okumura, Masahiko; Nakamura, Hiroki; Itakura, Mitsuhiro; Machida, Masahiko; Cooper, M. W. D.*

Scientific Reports (Internet), 12(1), p.9808_1 - 9808_11, 2022/06

https://doi.org/10.1038/s41598-022-13869-9

no abstracts in English

Dislocation core structure and motion in pure titanium and titanium alloys; A First-principles study

Tsuru, Tomohito; Itakura, Mitsuhiro; Yamaguchi, Masatake; Watanabe, Chihiro*; Miura, Hiromi*

Computational Materials Science, 203, p.111081_1 - 111081_9, 2022/02

https://doi.org/10.1016/j.commatsci.2021.111081

The deformation mode of some titanium (Ti) alloys differs from that of pure Ti due to the presence of alloying elements in -phase. Herein, we investigated all possible slip modes in pure Ti and the effects of Al and V solutes as typical additive elements on the dislocation motion in -Ti alloys using density functional theory (DFT) calculations. The stacking fault (SF) energies in possible slip planes indicated that both Al and V solutes reduce the SF energy in the basal plane and, in contrast, the Al solute increases the SF energy particularly in the prismatic plane. DFT calculations were subsequently performed to simulate dislocation core structures. The energy landscape of the transition between all possible dislocation core structures and the barriers for dislocation glide in various slip planes clarified the nature of dislocation motion in pure Ti. (i) the energy of prismatic core is higher than most stable pyramidal core, and thereby dislocations need to overcome the energy barrier of the cross-slip (22.8 meV/b) when they move in the prismatic plane, (ii) the energy difference between the prismatic and basal cores is larger (127 meV/b), that indicates the basal slip does not activate, (iii) however, the Peierls barrier for motion in the basal plane is not as high (16 meV/b). Direct calculations for the dislocation core around solutes revealed that both Al and V solutes facilitate dislocation motion in the basal plane by reducing the energy difference between the prismatic and basal cores. The effect of solutes characterizes the difference in the deformation mode of pure Ti and -Ti alloys.

Molecular dynamic simulations evaluating the effect of the stacking fault energy on defect formations in face-centered cubic metals subjected to high-energy particle irradiation

Terayama, Satoshi*; Iwase, Yuki*; Hayakawa, Sho*; Okita, Taira*; Itakura, Mitsuhiro; Suzuki, Katsuyuki*

Computational Materials Science, 195, p.110479_1 - 110479_12, 2021/07

https://doi.org/10.1016/j.commatsci.2021.110479

Hydrogen-trapping energy in screw and edge dislocations in aluminum; First-principles calculations

Yamaguchi, Masatake; Itakura, Mitsuhiro; Tsuru, Tomohito; Ebihara, Kenichi

Materials Transactions, 62(5), p.582 - 589, 2021/05

https://doi.org/10.2320/matertrans.MT-M2020375

no abstracts in English

Density functional theory study of solute cluster growth processes in Mg-Y-Zn LPSO alloys

Itakura, Mitsuhiro; Yamaguchi, Masatake; Egusa, Daisuke*; Abe, Eiji*

Acta Materialia, 203, p.116491_1 - 116491_9, 2021/01

https://doi.org/10.1016/j.actamat.2020.116491

Solute cluster in LPSO alloys plays a key role in their idiosyncratic plastic behavior such as kink formation and kink strengthening. Identifying the atomistic details of the cluster structure is a prerequisite for any atomistic modeling of LPSO alloys aiming for their improved strength and ductility, but there have been uncertainty about interstitial atom in the cluster. While density functional theory calculations have shown that inclusion of interstitial atom is energetically favorable, it has been unclear how the extra atom is provided, how much of the cluster have interstitial atoms, and what kind of element they are. In the present work we use density functional theory calculations to investigate the growth process of the solute cluster, specifically that of Mg-Y-Zn LPSO alloy, to determine the precise atomistic structure of solute cluster. We show that a pair of an interstitial atom and a vacancy is spontaneously created when a certain number of solute atoms are absorbed into the cluster, and all the full-grown cluster should include interstitial atom. We also show that interstitial atom is either Mg or Y atom, while Zn interstitial atom is extremely rare. These knowledge greatly simplifies atomistic modeling of solute clusters in Mg-Y-Zn alloy. Owing to the vacancies emitted from the cluster, vacancy density should be over-saturated in regions where solute clusters are growing, and the increased vacancy density accelerates cluster growth.

Hydrogen trapping in MgSi and AlFeCu intermetallic compounds in aluminum alloy; First-principles calculations

Yamaguchi, Masatake; Tsuru, Tomohito; Ebihara, Kenichi; Itakura, Mitsuhiro; Matsuda, Kenji*; Shimizu, Kazuyuki*; Toda, Hiroyuki*

Materials Transactions, 61(10), p.1907 - 1911, 2020/10

https://doi.org/10.2320/matertrans.MT-M2020201

no abstracts in English

Anomalous solution softening by unique energy balance mediated by kink mechanism in tungsten-rhenium alloys

Tsuru, Tomohito; Wakeda, Masato*; Suzudo, Tomoaki; Itakura, Mitsuhiro; Ogata, Shigenobu*

Journal of Applied Physics, 127(2), p.025101_1 - 025101_9, 2020/01

https://doi.org/10.1063/1.5131279

We explored softening/strengthening behavior in various solute in W matrix by density functional theory (DFT) calculations combined with solid solution model. As a result of DFT calculations for various solute, a clear trend was observed in the interaction energy between a solute and a screw dislocation, which has predominant influence on solid solution behavior. The predictions based on the solid solution model with DFT can reasonably reproduce the complicated softening/strengthening as a function of temperature and solute concentration. We conclude that this specific balance is the origin of macroscopic solid solution softening.