Fe-Ni many-body potential for metallurgical applications

A many-body interatomic potential for the Fe-Ni system is fitted, capable of describing both the ferritic and austenitic phase. The Fe-Ni system exhibits two stable ordered intermetallic phases, namely, L1(0) FeNi and L1(2) FeNi3, that are key issues to be tackled when creating a Fe-Ni potential consistent with thermodynamics. A procedure, based on a rigid lattice Ising model and the theory of correlation functions space, is developed to address all the intermetallics that are possible ground states of the system. While controlling the ground states of the system, the mixing enthalpy and defect properties were fitted. Both bcc and fcc defect properties are compared with density functional theory calculations and other potentials found in the literature. Finally, the potential is thermodynamically validated by constructing the alloy phase diagram. It is shown that the experimental phase diagram is reproduced reasonably well and that our potential gives a globally improved description of the Fe-Ni system in the whole concentration range with respect to the potentials found in the literature.