Diffusion mechanisms in ordered alloys—a detailed analysis of six-jump vacancy cycle in the B2 type lattice

Abstract

The diffusion coefficients of A and B atoms in the B2 type AB alloy are derived for the case that highly correlated vacancy jump cycle is operative. The effective frequencies of 100- and 110-type jumps of A and B atoms are expressed in terms of frequencies for individual vacancy jumps; the calculation is made by applying the concept of the mean first passage time known in the theory of stochastic processes. The correlation factors for diffusion of A and B atoms are calculated as a function of the wrong bond energy. The present analysis provides a sound and quantitative basis for the discussion of the ratio of diffusion coefficients for two types of atoms, D A D B , in ordered alloys.