Mobility of self-interstitial atom clusters in vanadium, tantalum and copper

Molecular dynamics (MD) simulations were performed to investigate the mobility of isolated self-interstitial atoms (SIAs) and their clusters in V, Ta and Cu. The migration of an isolated SIA is accompanied by rotation of a dumbbell axis to the close-packed direction of metals. The migration of an SIA cluster strongly depends on its structure. A relatively smaller-size cluster can migrate with simultaneous rotation of the axes of SIA pairs in the cluster to the same close-packed direction, which is the glissile configuration of the cluster. The transformation to the glissile configuration takes place more frequently than the dumbbell rotation of an isolated SIA in V and Ta, while it takes place less frequently in Cu. The smaller cluster can still change its diffusion direction. A greater-size cluster in the bcc metals, on the other hand, has the thermally stable form of densely-packed, parallel crowdions. It migrates without any changes of diffusion direction. The migration behavior of 7-SIAs clusters in Ta was also evaluated as a function of tensile and compressive strains.