Random-Walk Method for Calculating Correlation Factors: Tracer Diffusion by Divacancy and Impurity-Vacancy Pairs in Cubic Crystals

Abstract

The random-walk technique is extended in a way that allows correlation factors to be calculated in all cases where principle axes for diffusion can be found. The results are applicable both to tracer and to impurity diffusion. Explicit calculations are given of correlation factors for the diffusion of tracers by bound impurityvacancy pairs in fcc metals and NaCl-type ionic crystals, and by bound divacancy pairs in NaCl-type ionic crystals, CsCl-type ionic crystals, and fcc metals. Appropriate modifications for the "isotope effect" are made for the case of impurity-vacancy pairs.