Molecular dynamics simulations of point defect interactions in Fe–Cr alloys

Predicting the performance of Fe–Cr ferritic martensitic steels in fusion energy environments requires an understanding of point defect properties, including the influence of solutes, impurities and other defects on their migration behavior. This paper presents molecular dynamics simulations of the effect of Cr on the diffusion of single, di- and tri-interstitials in Fe–10%Cr alloys. Two Finnis–Sinclair-type potentials were used to model the Fe–Cr alloys, which alternately describe Cr as under- or over-sized in body-centered cubic Fe. In general, the diffusivity of the single interstitials and di- and tri-interstitial clusters was reduced in the Fe–10%Cr alloys, irrespective of interatomic potential, although the underlying mechanism was different. When Cr is undersized, interstitial diffusion is retarded through a trapping mechanism associated with bound Cr-interstitial (mixed dumbbell) complexes, whereas oversized Cr atoms retard interstitial diffusion by enhancing the rotation frequency away from one-dimensionally mobile 〈1 1 1〉 interstitial dumbbell configurations.