Structural, elastic, electronic, optic and thermodynamic properties of Li2BaSnX4 (X= S and Se) alloys: A first-principle study

Abstract

The structural, elastic, electronic, optic and thermodynamic properties of Li2BaSnS4 and Li2BaSnSe4 compounds are investigated by mean of the DFT-based FP-LAPW method as implemented in the Wien2k code. The exchange-correlation potential is treated with the GGA-WC approximation and the TB-mBJ approach. A volume optimization showed that the stannite structure is the most stable phase. The predicted structural parameters are in good agreement with the available experimental data. The independent elastic constants are calculated and used to verify the mechanical stability. In addition, the other elastic parameters such as the shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, Lamé’s constant and Pugh indicator are calculated. Electronics calculations reveal that our compounds are of a direct band gap semiconductor. The important optical functions such as the dielectric function, absorption coefficient, refractive index, and reflectivity have also been calculated and discussed and indicated that both compounds show weak transparency with a considerable reflectivity in the ultraviolet spectral domain. The thermodynamic properties such as the heat capacities, the coefficient of thermal expansion and the Debye temperature are also investigated, in the pressure range from 0 to 30 GPa and the temperature interval from 0 to 700 K.