LAUSR

Abstract The A15-type conventional superconductor Nb3Al alloys have been widely studied because of their high-performance superconductivity, which is generally considered a β-W3O-type structure with space group Pm 3 n at ambient pressure. In this study, four new crystalline phases of Nb3Al with space groups C2/m, I4/mmm, Pmmm and Pm 3 m were predicted using the particle swarm optimisation method. The mechanical parameters of the predicted phases under high pressure were also obtained using first-principle calculations. The competing enthalpies revealed that A15-type Nb3Al undergoes a phase transition from Pm 3 n to I4/mmm at 20 GPa pressure and then to Pmmm at 118 GPa. Although the Pmmm phase became mechanically unstable at 37.6 GPa via the Born–Huang criterion, mechanical analysis of the I4/mmm structure exhibited a greater toughness and superior mechanical properties than that of A15 Nb3Al. Phonon and Debye calculations also proved I4/mmm to be thermodynamically and dynamically stable at ambient pressures and low temperatures. The energetically favourable phases of Nb3Al that were discovered provided a more theoretical mechanistic basis for its preparation and development.