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 CV 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 CV 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.