Prediction of stable Cu structure and phase transition mechanism at ultra-high pressure: A comprehensive properties characterization by DFT calculation

Abstract

Evolutionary algorithms and the particle swarm optimization method have been used to predict stable and metastable Cu structures between 0 and 2000 GPa that have not been discussed in previous studies, Cmcm phase is identified to be the most energetically competitive candidate. Density functional theory calculations illustrate that face-centered Cu atoms in (0 1 0), (0 1(−) 0) and (1 1 0) move along the <0 0 1 > under the ultrahigh-pressure during the phase transformation from FCC (ambient pressure) to Cmcm (2000 GPa) structure. Phonon calculation further confirms the dynamical stability of this predicted structure, and the temperature dependence of electrical resistivity for Cmcm Cu will get reduced, predicted by phonon hardening with increasing pressure. The high-pressure structure still exhibits metallic behavior due to the finite electron DOS at the Fermi level, and the calculated elastic properties display superior bulk and shear modulus of Cmcm Cu with dramatic increase at 2000 GPa.