First-Principles Investigation of Structural, Electronic, Optical, Elastic, and Thermoelectric Properties of Cubic Francifluorite Perovskites FrXF3 (X = Si, Ge, and Sn) for Optoelectronic and Thermoelectric Device Applications

Abstract This study employs first-principles calculations based on Density Functional Theory (DFT), implemented in the Wien2k code, to investigate the structural, electronic, optical, elastic, and thermoelectric properties of FrXF 3 (X = Si, Ge, Sn) compounds. Various exchange–correlation functionals, including GGA-PBE, GGA-PBEsol, GGA-WC, and TB-mBJ, were utilized to achieve a comprehensive analysis. The electronic structure calculations reveal that all compounds exhibit semiconducting behavior with direct band gaps (R→R), ranging from 1.75 eV to 2.68 eV using TB-mBJ. Optical properties analysis shows strong responses in the visible to ultraviolet range, highlighting their potential for optoelectronic applications. Thermoelectric evaluations, including thermal and electrical conductivity, Seebeck coefficient, power factor, and figure of merit, indicate that FrXF 3 compounds possess significant thermoelectric potential, positioning them as promising candidates for thermoelectric applications.