Molecular dynamics simulations were used to investigate the mobility of isolated self-interstitial atoms and their clusters. The migration of an isolated self-interstitial atom was accompanied by the rotation of dumb-bell axes along the close-packed directions of the metal. The migration of a self-interstitial atom cluster depended strongly upon its structure. Smaller clusters could migrate, with simultaneous rotation of the axes of the self-interstitial atom pairs of the cluster into the same close-packed direction which was the glissile configuration of the cluster. Transformation into the glissile configuration took place more frequently than did the dumb-bell rotation of an isolated self-interstitial atom. A smaller cluster could still change its diffusion direction. On the other hand, larger clusters had the thermally stable form of densely-packed parallel crowdions. They migrated without any change in diffusion direction.

Mobility of Self-Interstitial Atom Clusters in Vanadium, Tantalum and Copper. K.Morishita, T.Diaz de la Rubia, A.Kimura: Nuclear Instruments and Methods in Physics Research B, 2001, 180[1-4], 66-71