First-principles evolutionary structural searches for new high-pressure phases of Nb₃Al

High cost and poor stability have inhibited the large-scale applications of high-temperature cuprate superconductors. Intermetallic niobium compounds such as Nb₃Sn and Nb₃Al attract significant research interest due to their potential superconducting applications. Herein, we have combined evolutionary algorithms with density functional theory to perform structural searches for ground-state crystal structures of Nb₃Al under high pressures. At ambient pressure and low temperature, a new phase with distorted Nb atomic chains is found to be energetically more stable than the well-known A15 phase. Because the Nb atomic chains are believed to be closely related to the superconducting properties, the electron-phonon coupling of this new phase has been further studied using density functional perturbation theory. Moreover, we identify a pressure-induced structural phase transition of Nb₃Al under high pressures. Base on ab-initio molecular dynamics simulations, the temperature effects on the structural phase transitions of Nb₃Al have also been investigated.