Probing the physical properties of M 2 LiCeF 6 (M = Rb and Cs) double perovskite compounds for prospective high-energy applications employing the DFT framework.

Herein, the optoelectronic, structural, thermoelectric, and elastic characteristics of M 2 LiCeF 6 (M = Rb and Cs) double perovskite compounds were investigated using ab initio modeling in the DFT framework. The Birch-Murnaghan fitting curve used for the optimization showed that these two compounds are structurally stable. The elastic properties of the M 2 LiCeF 6 (M = Rb and Cs) double perovskite compounds were examined using the IRelast code. The results showed that these two compounds possess mechanical stability, anisotropy, and toughness, and offer resistance to plastic deformation. The precise and accurate determination of their electronic properties was achieved via the Trans-Blaha-modified Becke-Johnson (TB-mBJ) approximation. The Rb 2 LiCeF 6 and Cs 2 LiCeF 6 compounds are narrow band gap semiconductors with band gaps of 0.6 eV and 0.8 eV at the high symmetrical points from ( Γ - M ), respectively, exhibiting an indirect nature. To further understand how the various states contribute to the different band structures, total and partial density of state (DOS) computations were performed. The optical properties in the energy range of 0-40 eV for Rb 2 LiCeF 6 and Cs 2 LiCeF 6 were explored. The selected materials show transparency in the low incident photon energy range and have large light absorption and transmission at higher photon energies. Thus, it can be concluded that Rb 2 LiCeF 6 and Cs 2 LiCeF 6 can be used in high-frequency UV devices based on their optical characteristics. Both materials exhibit high electrical conductivity, power factors, and figures of merit ( ZT ) and act as effective thermoelectric resources. To the best of our knowledge, this is the first theoretical research on the optoelectronic, structural, thermoelectric, and elastic features of M 2 LiCeF 6 (M = Rb and Cs).