Computer simulation of SIA migration in bcc and hcp metals

Abstract

A Molecular statics and dynamics study of self-interstitial diffusion mechanisms in model Fe, Mo (bcc) and Zr (hcp) is performed. Embedded-atom-method type interatomic potentials developed by the present authors are employed. Molecular dynamics simulations are carried out at constant energy and volume for different temperatures. Defect diffusion coefficients are computed and the migration jumps at both, low and relatively high temperatures, are qualitatively identified by simple visualization techniques. The relevance of crowdion-type interstitials is demonstrated in both hcp and bcc structures. Highly non-Arrhenius behavior is predicted for the basal diffusion in Zr. Also, the dynamically computed migration energies result roughly in half of the values computed using static techniques. This points to the difficulties of a straight application of Transition State Theory under conditions of moderately complex defect and/or energy barrier structures.