Elastic, phonon and thermodynamic properties of Mg–Ga compounds from first-principles calculations

Based on first-principles calculations within the projector augmented wave method, the elastic, phonon and thermodynamic properties of the Mg–Ga compounds have been investigated. The targeted compounds include the stable phases: Mg5Ga2, Mg2Ga, MgGa, O- MgGa2 (orthorhombic), Mg2Ga5 and metastable phase: H- MgGa2 (hexagonal). Utilizing the stress–strain method, the elastic stiffness matrix and elastic properties including bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio are calculated. By means of the quasiharmonic approach, the thermodynamic properties of the Mg–Ga compounds, including Gibbs energy, entropy, enthalpy, and heat capacity at constant pressure, have been predicted. These thermodynamic properties have been compared with the available experimental and CALPHAD dataset. Good agreements have been found between first-principles calculations and the experimental data, while there are some deviations between the present work and the CALPHAD dataset. The elastic and thermodynamic properties calculated in the present work yield a helpful insight into the lacking elastic properties, phase stability and less reliable experimental information.

► Thermodynamic properties for the compounds in the Mg–Ga system were studied.
► Elastic properties of the Mg–Ga compounds were calculated by the strain–stress method.
► Comparison with the CALPHAD results motivate further reassessment of the Mg–Ga system.
► The systematic predictions yield a helpful insight into developing novel Mg-based alloys.