Stability of a nonequilibrium phase in an immiscible Ag-Ni system studied by<i>ab initio</i>calculations and ion-beam-mixing experiment

Employing the Vienna ab initio simulation package (VASP), a possible nonequilibrium intermediate state located near ${\mathrm{Ag}}_{3}\mathrm{Ni}$ in the immiscible Ag-Ni system is predicted through calculating the total energy of six possible structures of ${A}_{3}B$ type as a function of their lattice constants. The predicted state is confirmed by the fact that a metastable hcp ${\mathrm{Ag}}_{3}\mathrm{Ni}$ phase was indeed obtained in the properly designed Ag-Ni multilayers upon 200 keV xenon ion irradiation at 77 K and its lattice constants determined by diffraction analysis were in good agreement with the calculated values.