Small interstitials clusters migration in bcc metals: A Molybdenum model

The migration mechanisms of small self-interstitial clusters in two models for bcc Molybdenum are studied by computer simulation. The research is pertinent to the stages after collision cascade collapse of radiation damage, when defects diffuse to sinks and agglomerate into bigger units. Among the interaction models considered, one is a rather standard many-body central forces potential; the other one includes angle contributions to the energy, which in principle is a more consistent representation of a bcc transition metal. Also, two techniques are employed: Molecular Dynamics and Monomer. The former provides global parameters of the diffusion process; the latter is a static technique to search the potential energy surface for saddle configurations, thus providing detailed information on transition events. Reasonable agreement is found among the techniques, though the connection between the static parameters with the dynamic ones may not be straightforward. The two interaction models result in both quantitative and qualitative differences; notably in some cases when the former are small the underlying microscopic mechanisms can be nevertheless different.