Self-interstitials in V and Mo

We report an extensive ab initio study of self-interstitials in V and Mo. Contrary to the widely accepted picture, the [111] dumbbell is found to be the most stable structure. The activated state for migration is the crowdion configuration, with an extremely low barrier (similar to0.01 eV), suggesting 1d (one-dimensional) diffusion at low temperatures and 3d diffusion at high temperature. In the case of Mo, the energy landscape between the [111] and [110] dumbbells is very shallow. Predicted migration energies and self-interstitial structures are consistent with experiment.