Metastable states in an equilibrium immiscible Ni–Ru system studied by ab initio calculation and ion mixing experiment

Under the framework of the Vienna ab initio simulation package, calculation results predicted that two energetic metastable states with either D019 or L12 structure were favored near the compositions of Ni3Ru and NiRu3, respectively, in the Ni–Ru system characterized by a positive heat of formation. Applying a far-from-equilibrium scheme of ion mixing, an hcp and an fcc metastable phases were indeed formed in the Ni75Ru25 and Ni25Ru75 multilayers, respectively, upon xenon ion irradiation at 77 K and their lattice constants determined by means of diffraction analysis were in good agreement with those from ab initio calculation.