Calculation of phonon spectra to predict the high-pressure metastable phase in an equilibrium immiscible Cu–Ta system

Abstract

Under the framework of lattice dynamics, the phonon spectra of the possible metastable Cu3Ta compounds at zero pressure are computed based on an n-body potential by fitting to some physical properties acquired from ab initio calculations. For the three ideal lattices, i.e., L12, D03, and D019, imaginary phonons appear along all high symmetry directions in the Brillouin zone and disappear while subjected to high pressure at about 2.7, 11.8, and 14.7GPa, respectively. Interestingly, one of the predicted compounds in an L12 structure has indeed been obtained by ion-beam mixing under an appropriate condition.