First-principle investigation of LiSrX (X=P and As) half-Heusler semiconductor compounds

Based on density functional theory, the structural and physical properties of LiSrX (X=P and As) half-Heusler semiconductor compounds have been studied. The obtained results of the ground state show that the LiSrX are chemically stable and exhibit semiconducting behavior with an indirect band gap for LiSrAs and a direct band gap for LiSrP. The values of elastic constants and their derivative parameters show that LiSrX are mechanically stable and have ductile nature. Furthermore, the phonon dispersion calculations show that LiSrX are dynamically stable in the ground state. The optical properties are investigated and discussed in detail. The obtained results show that LiSrX have strong absorption and low reflectivity in the visible and low ultraviolet regions. Thermoelectric properties of LiSrX (X=P, As) were calculated and evaluated. The Seebeck coefficient decreased with an increase in temperature, and the highest values are obtained in n-type doped about 3116.46 mu V/K and 3055 mu V K for LiSrP and LiSrAs. The value of 0.98 is achieved for figure of merit at 300K. The mechanical and dynamic stability, along with a strong absorption and low reflectivity in the visible and low ultraviolet regions, make these compounds more suitable as absorbers of solar cells and optoelectronic.