Ab initio phase stability of some cubic phases of ordered Ni-Fe alloys at high temperatures and pressures

Abstract

To address the temperature-induced stabilization of different phases, we studied some special structures of ordered Ni-Fe alloys by applying the recently developed self-consistent ab initio lattice dynamics approach. A simple but efficient scheme was also used to calculate the free energy and entropy. We found that the ordered structures with high nickel content are easier to stabilize at high temperature. Especially, the anharmonic part of free energy plays an important role in stabilizing the fcc-Ni3Fe structure at high temperatures and pressures. Finally, the dynamically stable regions of Ni3Fe compound are predicted in the phase diagram, and bcc-Ni3Fe phase is expected to be stable at high temperature and pressure.