Abstract
<title>Abstract</title> <p> Background This thesis presents a comprehensive ab-initio investigation. Here I have explored the structural, elastic, electronic, and optoelectronic properties of the two antimony-based double perovskite oxides which are Sr <sub>2</sub> PrSbO <sub>6</sub> and Sr <sub>2</sub> CeSbO <sub>6</sub> via DFT study by using WIEN2K computational package through full-potential linearized augmented plane-wave (FP-LAPW). Methods The structural optimization has been performed using the Birch-Murnaghan equation of state, the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential has been used for finding of band-gap, the elastic properties have been investigated by calculating the three independent elastic constants and the optical properties including the dielectric function, refractive index, extinction coefficient, absorption coefficient, optical conductivity, reflectivity, and electron energy loss function have been computed over the photon energy range of 0–14 eV. Results equilibrium lattice constants of 8.60 Å for Sr <sub>2</sub> PrSbO <sub>6</sub> and 8.58 Å for Sr <sub>2</sub> CeSbO <sub>6</sub> and both compounds crystallize in the monoclinic space group P2 <sub>1</sub> /n, consistent with experimental reports on the Sr <sub>2</sub> RESbO <sub>6</sub> family and the Goldschmidt tolerance factor computed for Sr <sub>2</sub> PrSbO <sub>6</sub> is 0.915 and for Sr <sub>2</sub> CeSbO <sub>6</sub> is 0.941which confirm assures the structural stability range. And direct band gaps of approximately 3.49 eV for Sr <sub>2</sub> PrSbO <sub>6</sub> and 3.52 eV for Sr <sub>2</sub> CeSbO <sub>6</sub> at the Gamma point while the density of states analysis indicates dominant contributions from O 2p orbitals in the valence band and Sb 5d states in the conduction band, with Pr 4f and Ce 4f states. Both of the compounds demonstrate strong ultraviolet (UV) absorption, high refractive indices in the 5–8 eV range. Conclusions Several important directions for future research work emerge from this research work and the experimental synthesis and characterization of Sr2PrSbO6 and Sr2CeSbO6 thin-films would provide crucial validation of the predicted properties and enable assessment of practical device performance. </p>