Mobility, interdiffusion, and tracer diffusion in lattice-gas models of two-component alloys

Abstract

The transport properties of lattice-gas models of alloys with two particle species are studied. The numbers of the particles and vacancies are conserved, and the two particle species have different exchange rates with the vacancies. The mobility and interdiffusion is described by the linear Onsager theory of transport. The Onsager coefficients are estimated from numerical simulations of the mobilities. A recently proposed relation between the Onsager coefficients of the random-alloy model is verified. The interdiffusion of the two species is directly monitored in the simulations; it is well described by the estimated Onsager coefficients. The results on interdiffusion are compared with simulation results on tracer diffusion. The interdiffusion cannot be expressed by the average, or the inverse average, of the tracer-diffusion coefficients. An exception is the case of identical transition rates where the interdiffusion coefficient is given by the tracer-diffusion coefficient.