Phase-field modeling of coupled dynamics of dislocation and hydrogen density fields in BCC iron based on first principles calculation

We construct a numerical model of the coupled evolution of hydrogen-concentration and defect fields in iron based on a phase-field (PF) microelasticity theory, with coupling of the long-range elastic interactions and short-range chemical interactions that control hydrogen and dislocation motion. To obtain the physical parameters included in the PF free-energy functional, the interaction energy between a hydrogen atom and dislocation core, the hydrogen-concentration dependence of misfit energy and eigenstrains are quantitatively determined using density-functional-theory (DFT) calculations. Based on these data, we investigate a time evolution of the hydrogen-dislocation interactions under applied external stress. For atomic interaction between hydrogen and dislocation core, it is observed that hydrogen concentration distribution is affected by the motion of dislocation.