Automatic kinetic Monte-Carlo modeling for impurity atom diffusion in grain boundary structure of tungsten material

摘要

Highlights ? Automatic kinetic Monte-Carlo modeling for grain boundary structure was developed. ? Realistic rough grain boundary structure was generated with the Voronoi diagram. ? Local minimum energy sites for impurity were found by localized molecular dynamics. ? Migration paths were found by the localized molecular dynamics also. ? The KMC simulation on the found migration paths was actually demonstrated. Abstract The diffusion process of hydrogen and helium in plasma-facing material depends on the grain boundary structures. Whether a grain boundary accelerates or limits the diffusion speed of these impurity atoms is not well understood. In the present work, we proposed the automatic modeling of a kinetic Monte-Carlo (KMC) simulation to treat an asymmetric grain boundary structure that corresponds to target samples used in fusion material experiments for retention and permeation. In this method, local minimum energy sites and migration paths for impurity atoms in the grain boundary structure are automatically found using localized molecular dynamics. The grain boundary structure was generated with the Voronoi diagram. Consequently, we demonstrate that the KMC simulation for the diffusion process of impurity atoms in the generated grain boundary structure of tungsten material can be performed.