The diffusion process in a $A$-$B$ binary alloy with $B2\mathrm{}$ order is studied by atomistic Monte Carlo simulations using a vacancy mechanism. The chosen ordering energies were taken from neutron scattering experiments and ensure a phase diagram close to that of the real Fe-Al system. The dynamics was introduced by one single vacancy jumping to nearest-neighbor sites. Employing different jump-energy evaluations for the exchange vacancy and atom, we determined diffusion constants as a function of temperature and investigated the mobility of antiphase boundaries. While the different jump-energy evaluations yielded a similar behavior of the diffusion constant above $T_c,$ we found a more complex influence of the evaluation on the diffusion constant below $T_c.$ Finally, the autocorrelation function of the atoms was calculated and compared with measurements on ${\mathrm{Fe}}_{50}{\mathrm{Al}}_{50}$ done by quasielastic Mössbauer spectroscopy. A similarity between the simulated and the experimentally obtained autocorrelation function is observed despite the simplicity of the jump model used.

• Received 21 January 1998

DOI:https://doi.org/10.1103/PhysRevB.58.3082