Self-interstitial transport in vanadium

Abstract: We study the diffusion of self-interstitial atoms (SIAs) and SIA clusters in vanadium via molecular dynamics simulations with an improved Finnis–Sinclair potential (fit to first-principles results for SIA structure and energetics). The present results demonstrate that single SIAs exist in a 〈111〉-dumbbell configuration and migrate easily along 〈111〉 directions. Changes of direction through rotations into other 〈111〉 directions are infrequent at low temperatures, but become prominent at higher temperatures, thereby changing the migration path from predominantly one-dimensional to almost isotropically three-dimensional. SIA clusters (i.e., clusters of 〈111〉-dumbbells) can be described as perfect prismatic dislocation loops with Burgers vector and habit planes of 1/2〈111〉{220} that migrate only along their glide cylinder. SIA clusters also migrate along 〈111〉-directions, but do not rotate. Both single SIAs and their clusters exhibit a highly non-Arrhenius diffusivity, which originates from a combination of a temperature dependent correlation factor and the presence of very low migration barriers. At low temperature, the diffusion is approximately Arrhenius, while above room temperature, the diffusivity is a linear function of temperature. A simple model is proposed to describe these diffusion regimes and the transition between them. [Copyright &y& Elsevier]