Chemical diffusion was investigated via the computer simulation of an Ising binary alloy in which an equilibrium concentration of vacancies was established and maintained. The equilibrium was set up by using a so-called 2-phase equilibrium approach. The thermodynamic factors and the intrinsic diffusion coefficient were calculated on the basis of the simulated data. It was found that, instead of just a single thermodynamic factor, as in the case of a binary system with a vanishingly small vacancy concentration, there were usually 2 different thermodynamic factors. Monte Carlo results showed that, when the vacancy concentration was not negligible (greater than 1%), it was no longer possible to treat the thermodynamic factors for chemical diffusion of the A and B components as a single factor.

Z.Qin, G.E.Murch: Philosophical Magazine A, 1995, 71[2], 323-32