Migration of point defects along a dissociated edge dislocation in copper: A molecular dynamics study of pipe diffusion

Abstract

Pipe diffusion along a dissociated edge dislocation in copper is investigated by molecular dynamics simulation. The formation energies of a vacancy and an interstitial in the cores and the fault ribbon are calculated by quasi-dynamics relaxation at 0 K. The diffusion rates of these defects are calculated at high temperatures by counting the number of atomic jumps due to the migration of the defects. The variation in the diffusion coefficients with the inverse of the temperature yields the migration energies for pipe diffusion, and it is interesting to note that the value of the energy obtained for the interstitial is comparable with the bulk value. Contrary to current assumptions in favour of a vacancy mechanism, we find that the two types of defect may contribute comparably with pipe diffusion since their activation energies are very close. Owing to the extension of the cores, the trajectories of the migrating defects involve not only the partials but also the stacking-fault ribbon. For this reason, pipe diffusion is slower when the dislocations are dissociated.