First-principles investigation on the mechanical, vibrational and thermodynamics properties of AuCu3-type X3Sc (X = Al, Ga, In) intermetallic compounds

Abstract

First-principles calculation is performed to systematically study the structural stabilities, mechanical properties, vibrational and thermodynamic properties for AuCu3-type Al3Sc, Ga3Sc and In3Sc compounds. The calculated formation enthalpy and cohesive energy indicate that these compounds all have the high thermodynamics stability. The elastic constants are satisfied with mechanical stability criteria. The mechanical parameters predict that Al3Sc has higher hardness than other two compounds. In the meantime, Al3Sc possess brittle nature, but Ga3Sc and In3Sc are ductile. The mechanical anisotropy is predicted by anisotropic constants AG, AU, AZ and 3D curved surface of Young’s moduli. These results show that Al3Sc is isotropic, but Ga3Sc and In3Sc are elastically anisotropic. The sound velocities in different directions and Debye temperature for Al3Sc, Ga3Sc and In3Sc are also predicted. The calculated vibrational properties indicate that three compounds would keep the dynamical stability in AuCu3 structure. Finally, we also calculate the thermodynamics properties and give out the relationships between thermal parameters and temperature.