Mechanical and thermodynamic properties of Al3Sc and Al3Li precipitates in Al-Li-Sc alloys from first-principles calculations

The mechanical, electronic and thermodynamic properties of L12-type Al3Sc and Al3Li precipitates have been investigated from first-principles method. The calculated equilibrium parameters such as lattice constants are in good agreement with the available experimental results and other theoretical reports. It is found that the Al3Sc exhibits a higher structural stability and stronger alloying ability than that of Al3Li since the Al3Sc possesses the lower cohesive energy and formation enthalpy. Mechanical parameters, such as the bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio ν and universal anisotropic index AU are determined by the Voigt-Reuss-Hill approximation. In addition, the anisotropic sound velocity, Debye temperature, density of states and charge density distribution of the two precipitates are studied. The calculations associated with phonon properties confirm the dynamical stability of the L12-type structures studied. Finally, the temperature-dependent behaviors of thermodynamic properties of the two precipitates are determined within the quasi-harmonic approximation.