The time correlation function which was associated with the phenomenological coefficients for matter transport in a simple cubic binary random alloy with a very small vacancy content was calculated, by means of Monte Carlo simulations, for a range of concentrations with the same atomic jump frequency ratio of 10:1. The corresponding phenomenological coefficients were found to be in good agreement with earlier simulation results which were based on the Einstein formulae. Three approximations to the time correlation function, which led to well-known approximations to the phenomenological coefficients, were deduced from kinetic equations and were compared with the simulation results. None of these approximations was thought to be entirely satisfactory. Even a self-consistent approximation to the solution of the kinetic equations, which led to very accurate phenomenological coefficients, did not furnish a good description of the time correlation function. Simulations of such time correlation functions also permitted the calculation of the frequency dependence of the phenomenological coefficients.

Z.Qin, A.R.Allnatt, E.L.Allnatt: Philosophical Magazine A, 1995, 71[2], 291-306