COMPUTER-SIMULATION OF CHEMICAL DIFFUSION IN A BINARY ALLOY WITH AN EQUILIBRIUM CONCENTRATION OF VACANCIES

In the present work, chemical diffusion is explored by computer simulation in a (Ising) binary alloy wherein an equilibrium concentration of vacancies is established and maintained. The equilibrium was set up using a 'two-phase equilibrium' approach. The thermodynamic factors and intrinsic diffusion coefficient were calculated on the basis of the simulated data. Instead of only one thermodynamic factor as in the binary system with a vanishingly small vacancy concentration, there are, in general, two different thermodynamic factors. Monte Carlo results show that, whenever the vacancy concentration is not negligible (greater than 1%), one can no longer treat the thermodynamic factors for chemical diffusion of the components A and B as a single factor.