First-principles predictions of stable structure of AuAl2 under high pressure

Abstract

Pressure-induced phase transformation of AuAl2 had been theoretically investigated by using crystal structure searching technique combined with first-principles calculations. The predicted orthorhombic Pbnm structure possesses a larger structural stability with pressure larger than 17 GPa, and transition pressure is consistent with experimental value. The simulated x-ray diffraction patterns of Pbnm structure are in satisfactory agreement with the experimental data. The specific density of states indicate that there are discontinuous changes of electrical resistance accompanying with phase transition, and these are in accordance with experimental observations. Moreover, phonon dispersions and elastic constants reveal that Pbnm structure has dynamical and mechanical stabilities. The directional dependence of Young's modulus was analyzed and Pbnm phase has a larger elastic anisotropy.