Concentrations of Atomic Defects in B2FexAl1−x. An Ab‐Initio Study

The concentrations of various atomic defects are calculated within the framework of a grand canonical formalism for the ordered compound Fe x Al 1− x with B2 structure as functions of temperature and composition. The input parameters for the grand canonical formalism are determined by the ab‐initio mixed‐basis pseudopotential theory in local‐density approximation. It is shown that Fe x Al 1− x is neither a compound with pure antisite disorder nor a compound with pure triple‐defect disorder but that it exhibits a hybrid behaviour in which vacancies on the Fe sublattice and antisite atoms on both sublattices appear. The concentration of vacancies on the Al sublattice is negligibly small. The implications of this result for the modelling of diffusion mechanisms in Fe x Al 1− x are discussed.