Meso-timescale atomistic simulations on coalescence process of He bubbles in Fe by SEAKMC method

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

Computational Materials Science, 229, p.112389_1 - 112389_9, 2023/10

https://doi.org/10.1016/j.commatsci.2023.112389

He bubbles are characteristic microstructures under fusion reactor conditions. They approach and coalesce through their own migration, which significantly impacts the microstructure and material properties. However, these processes, which involve multiple migrations of metal atoms, cannot be treated by molecular dynamics (MD) due to its timescale limitation. In this study, self-evolving atomistic kinetic Monte Carlo (SEAKMC) was used to expand the timescale and reproduce bubble coalescences in Fe. To enhance selections of events that led to the process by avoiding trivial events with an extremely low activation energy such as tiny vibrations of a He atom or short-range displacements of the Fe atom, we introduced two algorithms into SEAKMC, a two-step saddle point search for the former measure and setting a threshold for a displacement distance of the Fe atom for the latter. Furthermore, by adding another algorithm to set an upper bound for the activation energy to prevent selections of events with an impractically high activation energy, we succeeded to reproduce the change in the configuration from dumbbell to elliptical up to a simulated time of s, 8 orders longer than MD timescales. The developed method is effective for analyzing microstructures of metallic materials containing light elements and is the only method that can reach timescales comparable to those of experiments.

Molecular dynamics simulation to elucidate effects of spatial geometry on interactions between an edge dislocation and rigid, impenetrable precipitate in Cu

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

Computational Materials Science, 215, p.111806_1 - 111806_8, 2022/12

https://doi.org/10.1016/j.commatsci.2022.111806

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

Atomistic simulations for the effects of stacking fault energy on defect formations by displacement cascades in FCC metals under Poisson's deformation

Hayakawa, Sho*; Okita, Taira*; Itakura, Mitsuhiro; Kawabata, Tomoya*; Suzuki, Katsuyuki*

Journal of Materials Science, 54(16), p.11096 - 11110, 2019/08

https://doi.org/10.1007/s10853-019-03688-1

Atomistic study of interaction between a dislocation and a defect cluster in BCC-Fe

Hayakawa, Sho; Okita, Taira*; Itakura, Mitsuhiro; Haixuan, X.*; Osetsky, Y.*

no journal, , 

In this research we have constructed an atomistic model of three-dimensional motion of an interstitial cluster via a conservative climb toward a dislocation, which is a key process for void swelling, one of the serious material degradation for nuclear power plant. We also conducted a comparison of results obtained by the model with that by the molecular dynamics. Details of the prediction model and the comparison results will be given in the presentation. This study leads to provide new atomistic insight about the three-dimensional motion of an interstitial cluster, which had been unclear for a long time, and would certainly contribute to the prediction model of mechanical property degradation of nuclear materials.