Calculated structural, elastic and electronic properties of SiX2O4 (X = Mg, Zn, Cd) compounds under pressure

Abstract

Using first-principles density functional calculations, the effect of high pressures, up to 30 GPa, on the structural, elastic and electronic properties of SiX2O4, with X = Mg, Zn and Cd, was studied by means of the pseudo-potential plane-waves method. We used both the local density approximation and the generalized gradient approximation to the exchange-correlation approximation energy. The results of bulk properties, including lattice constants, internal parameters, bulk modulus and derivatives, are obtained. The elastic constants and their pressure dependence are calculated using the static finite strain technique. We derived the bulk modulus, shear modulus, Young's modulus and Poisson's ratio for ideal polycrystalline SiX2O3 aggregates. We estimated the Debye temperature of SiX2O4 from the average sound velocity. Band structure, density of states and pressure coefficients of some gaps are also given. This is the first quantitative theoretical prediction of the elastic and electronic properties of SiMg2O4, SiZn2O4 and SiCd2O4 compounds, and still awaits experimental confirmation.