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This paper stuides the elastic constants and some thermodynamic properties of Mg_2Si_xSn_(n-1)(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 Mg_2Si_xSn_(n-1) were calculated.It shows that,at 273 K,the elastic constants of Mg_2Si and Mg_2Sn 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 Mg_2Si and Mg_2Si_(0.5)Sn_(0.5) on pressure were discussed.Through the quasi-harmonic Debye model,in which phononic effects were considered,the specific heat capacities of Mg_2Si_xSn_(1-x) at constant volume and constant pressure were calculated.The calculated specific heat capacities are well consistent with the previous experimental data.
This paper stuides the elastic constants and some thermodynamic properties of Mg_2Si_xSn_ (n-1) (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 Mg_2Si_xSn_ (n-1) were calculated. It shows that at 273 K, the elastic constants of Mg_2Si and Mg_2Sn 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 Mg_2Si and Mg_2Si_ (0.5) Sn_ (0.5) on pressure were discussed. Through the quasi-harmonic Debye model , in which phononic effects were considered, the specific heat capacities of Mg_2Si_xSn_ (1-x) at constant volume and constant pressure were calculated. The calculated specific heat capacities are well consistent with the previou s experimental data.