Structural stability of high-pressure phase in the immiscible Cu-Nb system studied by lattice dynamics calculation

For the equilibrium immiscible Nb-Cu system, first-principles calculations are performed to obtain the phonon spectra and density of states of the fcc-like L12 CuNb3 at zero pressure and the results indicate that the L12 CuNb3 is unstable, as there appears imaginary phonons. The stability of the L12 CuNb3 is therefore further calculated as a function of pressure and the results reveal that the L12 CuNb3 could be a high-pressure stable phase, as the related imaginary phonons disappear at high pressure.