Elastic constants and thermodynamic properties of Mg₂Si_xSn_1-x from first-principles calculations

This paper stuides the elastic constants and some thermodynamic properties of Mg₂Si_xSn_1-x (x=0, 0.25, 0.5, 0.75, 1) compounds by first-principles total energy calculations using the pseudo-potential plane-waves approach based on density functional theory, within the generalized gradient approximation for the exchange and correlation potential. The elastic constants of Mg₂Si_xSn_1-x were calculated. It shows that, at 273 K, the elastic constants of Mg₂Si and Mg₂Sn are well consistent with previous experimental data. The isotropy decreases with increasing Sn content. The dependences of the elastic constants, the bulk modulus, the shear modulus and the Debye temperatures of Mg₂Si and Mg₂Si_0.5Sn_0.5 on pressure were discussed. Through the quasi-harmonic Debye model, in which phononic effects were considered, the specific heat capacities of Mg₂Si_xSn_1-x at constant volume and constant pressure were calculated. The calculated specific heat capacities are well consistent with the previous experimental data.