First-principles study for ordering and phase separation in the Fe-Pd system

The main features of the phase diagram of the Fe-Pd system are characterized by phase separation in the Fe-rich region and appearance of two ordered phases in the Pd-rich region. The total-energy FLAPW electronic structure calculations are attempted on a set of selected ordered compounds as well as Fe and Pd to clarify the origin of these features. It is revealed that (i) magnetism plays a dominant role in the phase stability of the system and (ii) the system has an intrinsically large driving force for ordering, while the elastic energy originating from size mismatch causes the phase separation in the Fe-rich portion.