First-principles investigation of structural, elastic, thermodynamic, electronic and optical properties of lead-free double perovskites halides: Cs2LiYX6 (X = Br, I)

We present a comprehensive first-principles study on the physical properties of the lead-free double perovskites halides, Cs2LiYX6 (X = Br, I). Our calculated results of lattice constants (a(0)) of both compounds are in nice agreement with the reported experimental and theoretical investigations. The predicted band structures of both compounds show that both compounds are wide and direct bandgap materials at T-point. Similarly, our computed results of elastic analysis predict that the investigated materials are elastically anisotropic, mechanically stable, and of ductile nature. The results of optical parameters such as absorption coefficients, refractive index, optical conductivity, optical reflectivity, electron energy loss, and extinction coefficients for an energy range of 0-14 eV are calculated and analyzed as well. The analysis of obtained results of wide and direct band gaps as well as optical parameters particularly absorption coefficients reflect the suitability of both compounds for ultraviolet high-frequency device applications.