Diffusion in a binary alloy, with B2 ordering, was studied by using atomistic Monte Carlo simulations and an assumed vacancy mechanism. The ordering energies were deduced from neutron-scattering experiments, and modelled a phase diagram which was close to that of the Fe-Al system. Dynamics were introduced by the jumping of a single vacancy to nearest-neighbor sites. By making various jump-energy assumptions concerning the vacancy-atom exchange, the diffusion constants were determined as a function of temperature and the mobility of antiphase boundaries was investigated. The various assumptions which were made with regard to the jump-energy led to similar behaviors of the diffusion constant above Tc. A more complicated effect of the assumed jump energies, upon the diffusion constant, was observed below Tc. The auto-correlation function for the atoms was calculated, and was compared with quasi-elastic Mössbauer spectroscopic measurements of Fe50Al50. A similarity between the simulated and experimentally obtained auto-correlation functions was observed in spite of the simplicity of the jump model which was used.

Monte Carlo Simulation of Diffusion in a B2-Ordered Model Alloy R.Weinkamer, P.Fratzl, B.Sepiol, G.Vogl: Physical Review B, 1998, 58[6], 3082-8