A new extension of the self-consistent mean field theory was developed to describe diffusion in dilute alloys; special attention being paid to the problem of self-diffusion in the presence of solute atoms. Starting from a microscopic model of the atom-vacancy exchange frequency, including nearest-neighbour interactions, kinetic equations were derived from a master equation. The non-equilibrium distribution function was expressed by time-dependent effective interactions. Their range of interaction controlled the level of description of the paths of a vacancy after a first exchange. In contrast to previous models devoted to concentrated alloys, the present formulation reproduced, in the final result, several exchange frequencies that were associated with a given atom; depending upon the chemical species of the nearby atoms. A first approximation, restricted to nearest-neighbour effective interactions, yielded analytical expressions for the transport coefficients of a face-centered cubic dilute binary alloy. The phenomenological coefficients were equivalent to those obtained by using the 5-frequency model within the first-shell approximation. A new expression for the self-diffusion coefficient was proposed and was compared to Monte Carlo simulations using the same atomic diffusion model. The self-consistent mean field theory reproduced the main tendencies of the Monte Carlo simulations; in particular, within the random alloy region where recent 5-frequency models had not been satisfactory. Limitations and improvements to the self-consistent mean field approach were easily related to the range of the effective interactions which was considered.

A Mean Field Theory for Diffusion in a Dilute Multi-Component Alloy - a New Model for the Effect of Solutes on Self-Diffusion. M.Nastar: Philosophical Magazine, 2005, 85[32], 3767-94