First-principles calculations of hydrogen trapping energy at an edge dislocation core in iron

山口 正剛   ; 海老原 健一   ; 板倉 充洋  

Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro

Understanding the mechanism of hydrogen embrittlement in steel requires knowledge of hydrogen trapping behavior at lattice defects in iron. However, first-principles calculations using atomistic modeling of an edge dislocation core in body-centered cubic ferromagnetic iron remain challenging because they require several hundred atoms for the core structure and must account for the influence of a long-range strain field around the core. We calculated the hydrogen trapping energies at iron's most common edge dislocation core from first principles; we used a relatively small unit cell (378 Fe atoms) containing two cores of opposite signs with periodic boundary conditions. The cell size dependence of the hydrogen trapping energies was estimated using a recently developed machine-learning neural network potential for the iron-hydrogen system. Although the small cell size led to overestimating the trapping energy, it was less than 10 %.