Structure stability and magnetic properties of the Ni–Ru system studied by ab initio and molecular dynamics calculations together with ion beam mixing

Ab initio calculations reveal that it is energetically favorable for Ni3Ru and NiRu3 alloys to be of the D019 structure, while it is energetically favorable for NiRu alloy to be of the L10 structure. Moreover, Ni3Ru alloys of A15 and D019 structures are both ferromagnetic, while NiRu alloy of the L12 structure can be ferromagnetic when its lattice constant is greater than 3.623 Å. Based on a newly derived Ni–Ru potential, molecular dynamics simulations predict that face-centered cubic and hexagonal close packing are metastable structures for the Ni-rich and Ru-rich alloy phases, respectively, and that under nonequilibrium conditions the Ni–Ru system may behave as if it features an isomorphous phase diagram. Interestingly, the prediction is in agreement with observations obtained from ion beam mixing of multiple metal layers.