A study was made of the diffusion of self-interstitial atoms and self-interstitial clusters in vanadium via molecular dynamics simulations involving an improved Finnis-Sinclair potential fitted to first-principles results for self-interstitial atom structure and energetics. The present results demonstrated that single self-interstitial atoms existed in a <111>-dumb-bell configuration and migrated easily along <111> directions. Changes of direction by rotations into other <111> directions were infrequent at low temperatures, but became prominent at higher temperatures, thereby changing the migration path from predominantly one-dimensional to almost isotropically three-dimensional. Self-interstitial atom clusters (of <111>-dumb-bells) could be described as perfect prismatic dislocation loops with Burgers vector and habit planes of 1/2<111>{220} that migrated only along their glide cylinder. Self-interstitial atom clusters also migrated along <111>-directions, but did not rotate. Both single self-interstitial atoms and their clusters exhibited a highly non-Arrhenius diffusivity which originated from the combination of a temperature-dependent correlation factor and the presence of very low migration barriers. At low temperatures, the diffusion was approximately Arrhenius-like. Above room temperature, the diffusivity was a linear function of temperature. A simple model was proposed for describing these diffusion regimes and the transition between them.

Self-Interstitial Transport in Vanadium. Zepeda-Ruiz, L.A., Rottler, J., Wirth, B.D., Car, R., Srolovitz, D.J.: Acta Materialia, 2005, 53[7], 1985-94