Elastic and Thermodynamic Properties Prediction of Mg₂Sn and MgTe by First-Principle Calculation and Quasi-Harmonic Debye Model

Structural stability of MgTe is discussed in terms of total energy and formation energy. Mechanical and thermodynamic properties of Mg₂Sn and MgTe were investigated using first-principle calculations and the quasi-harmonic Debye model. The calculated results indicate that the bulk (B) and shear (G) moduli increase linearly with increasing pressure. In the pressure range of 0–10 GPa, the ratio of G/B decrease for Mg₂Sn from 0.66 to 0.568 and increase for MgTe from 0.262 to 0.327. Low-frequency acoustic branches and high-frequency optical branches are separated for both Mg₂Sn and MgTe. Activity of the branches determines the trend of Debye temperature with increasing temperature. The top values of C_V for Mg₂Sn and MgTe are 74.5 J mol⁻¹ K⁻¹ and 23.8 J mol⁻¹ K⁻¹, respectively, at T < 400 K, and then these values remain constant. The C_V value of MgTe is three times lower than that of Mg₂Sn. This result indicates that MgTe is expected to have lower lattice thermal conductivity, and this agrees well with the calculated results of electronic structure.