Behaviour of the diffusion vacancy-wind factors in the concentrated random alloy

Abstract

In this paper, the vacancy-wind factors which appear in the well known expressions relating the interdiffusion coefficient and intrinsic diffusion coefficients to the tracer diffusion coefficients are examined in the context of the random alloy model. It is shown by Monte Carlo simulation that the formalism of Moleko et al. provides a much better description of these factors than the well known and commonly used formalism of Manning. Even when the ratio of the tracer diffusion coefficients is relatively close to unity, it is preferable to use the Moleko et al. formalism. The latter formalism is re-expressed in this paper to be suitable for direct experimental use in determining vacancy-wind factors. The limiting behaviour of the ratios of the tracer diffusivities and intrinsic diffusivities is also discussed. In the latter case the ratio is given simply (and generally) by the ratio of the exchange frequencies.