A study was made of diffusion via a vacancy mechanism in an A-B binary alloy with B2 order. The starting point of the Monte Carlo simulations was Mössbauer spectroscopic and nuclear resonant scattering data on stoichiometric B2-ordered FeAl. These had revealed a non-obvious jump model for Fe atoms. That is, there was a preference for effective jumps to third-nearest neighbor sites rather than second-nearest neighbor sites. Ordering energies were chosen, for the simulations, that produced a phase diagram which was close to that of the real Fe-Al system. By allowing the vacancy to exchange with nearest-neighbor atoms only, perfect agreement was obtained between simulation and experiment for the case where interactions between vacancies and atoms were included. It was suggested that the unusual features of the Fe diffusion arose from highly correlated vacancy paths which were due to interaction of the vacancy with locally disordered areas, in the B2-lattice, that were created by vacancy-movement itself.

Monte Carlo Simulation of Mössbauer Spectra in Diffusion Investigations. R.Weinkamer, P.Fratzl, B.Sepiol, G.Vogl: Physical Review B, 1999, 59[13], 8622-5