Extending the timescale in molecular simulations on microstructural evolution of structural materials

2023 Fiscal Year Final Research Report

• Project/Area Number: 20H02662
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: The University of Tokyo
• Principal Investigator: OKITA Taira 東京大学, 大学院工学系研究科(工学部), 特任准教授 (50401146)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: モンテカルロ法 / 結晶欠陥 / 拡散 / カスケード損傷 / on-the-fly モンテカルロ法

Outline of Final Research Achievements

In this study, we developed two schemes to accelerate saddle process searches (SPS) against Self-Evolving atomistic kinetic kinetic Monte Carlo, which is one of the computational methods for time evolution based on state-to-state dynamics by performing SPS at each time step. It enabled to reproduce phenomena on longer time scales than can be handled by molecular dynamics while maintaining the atomistic fidelity. We applied this newly-developed method to clusters of self-interstitial atoms formed under a high-energy particle irradiation, and we successfully observed their conversion processes to stable configurations such as faulted dislocation loops or perfect loops with multiple atomistic diffusion for the first time in the world.

Free Research Field

原子力材料

Academic Significance and Societal Importance of the Research Achievements

従来の分子動力学（MD）では時間スケールが通常100ピコ秒オーダーであったため、再現できる現象が極めて限られていた。しかしながら、本研究で開発した手法はMDと同等の精度を確保しつつ、時間スケールを大幅に拡張することも可能なため、原子レベルの挙動に基づいて複数回の拡散過程を伴うナノ組織発達を解析する上で大変強力な手法と考えられる。