Modeling of phosphorus transport by interstitial dumbbell in α-iron using first-principles-based kinetic monte carlo

Abstract

We have evaluated the diffusion coefficient of phosphorus in a-iron transported in the form of a mixed dumbbell using a kinetic Monte Carlo simulation based on first-principles calculations. The evaluated diffusion coefficient has been compared with both that for the migration mode via octahedral interstitial sites and that for the migration mode of the vacancy mechanism estimated previously using a first-principles-based kinetic Monte Carlo simulation. As a result, we have confirmed that the phosphorus diffusion by the two interstitial migration modes is much faster than that of the vacancy migration mode. In addition, by applying the rate-theory model incorporating the evaluated coefficients to the simulation of irradiation-induced grain-boundary phosphorus segregation, it was made clear that modifications are required to the previous model for GB P segregation and for evaluating GB P coverage.