Correlation factor for diffusion in cubic crystals with solute-vacancy interactions of arbitrary range

Abstract

A formalism using a double Laplace Fourier transform of the transport equation yields the return probabilities of the vacancy in the vicinity of the tracer atom in the presence of solute-vacancy interactions of arbitrary extension. Studying model cases, it is shown that taking into account the full range of the interaction may change noticeably the correlation factor. The latter depends tightly on the pattern of migration barriers which is chosen to describe the vacancy jumps around the tracer atom. A thorough ab initio evaluation of all barriers is rarely available in the literature. It is shown that approximations often used to overcome this lack of information can be misleading. The examination of dilute systems recently studied shows that the interactions within the first three neighbour shells dictate the final value with a good precision. The main improvement of the modelling comes from dropping the restrictive assumption which impose an equal value to the jump frequencies leading to a dissociation of the solute-vacancy pair.