The reaction paths between low-energy configurations of a self-interstitial in crystalline material were studied by using 2 methods. One of these methods (discretized path) had not previously been applied to the study of defect mobility. When considering 2 minimum-energy defect configurations, the discretized path method was shown to provide an efficient means for determining the saddle-point configuration along the reaction path. On the other hand, for a known transition state configuration, eigen-mode analysis permitted the location of the stable configurations that were connected by the saddle. Results which were obtained here, by using the Stillinger-Weber potential model, revealed 2 basic mechanisms of self-interstitial migration. These were a jump process that involved the center of a distributed self-interstitial, and a rotation of the defect configuration about this center. Since the lowest activation energy that was indicated by this saddle-point analysis corresponded to a transition which did not involve the defect configuration of lowest energy, it was suggested that separate consideration of the formation and migration components of a defect activation energy could be misleading in identifying the predominant mobility mechanism.

M.Nastar, V.V.Bulatov, S.Yip: Physical Review B, 1996, 53[20], 13521-7