Comparative study of nonequilibrium phase of A₃B and AB₃ types in the Ni-Mo system by first principles and thermodynamic calculations

In the Ni-Mo system, two possible nonequilibrium states located near Ni₃Mo were predicted through calculation of the total energies of eight possible structures of the A₃B type as a function of their lattice constant(s) by applying the Vienna ab initio simulation package. Comparatively, Gibbs free energy diagrams were constructed from Miedema's model and, in general, the calculated results were in accordance with the prediction from ab initio calculation. Besides, the prediction of one of the nonequilibrium states was in agreement with the fact that a metastable hexagonal-close-packed Ni₃Mo phase was indeed observed in Ni₇₅Mo₂₅ multilayer films upon thermal annealing, and calculated lattice constants matched well with those determined by diffraction analysis in experiments as well.