Metastability of an immiscible Cu-Mo system calculated from first-principles and a derived<i>n</i>-body potential

Abstract

An ab initio calculation is performed to predict the structures, lattice constants, and cohesive energies of the metastable ${\mathrm{Cu}}_{75}{\mathrm{Mo}}_{25},$ ${\mathrm{Cu}}_{50}{\mathrm{Mo}}_{50},$ and ${\mathrm{Cu}}_{25}{\mathrm{Mo}}_{75}$ phases. With the aid of an ab initio calculation, an n-body Cu-Mo potential is derived and proven to be realistic in reproducing some intrinsic properties of the metastable Cu-Mo phases. Based on the Cu-Mo potential, a molecular dynamics simulation reveals that a crystal-to-amorphous transition takes place in a Cu-rich fcc solid solution when the solute concentration reaches/exceeds a critical value of 25 at. % Mo. Moreover, a molecular dynamics simulation also predicts the formation of metastable fcc and bcc Cu-Mo phases and determines the heats of formation of both crystalline and amorphous phases, thus constructing an energy diagram of the Cu-Mo system over the entire composition range. The calculation/simulation results are compared with the experimental observations, and the agreements between them are fairly good.