Computational analysis on structural, opto-electronic and thermo-electronic properties of Cs ₂ CuBiX ₆ (X = Br/I) compounds

This paper represents the influence of structural, electronic, optical and thermal properties of Halide double perovskites (HDP) Cs2CuBiBr6 and Cs2CuBiI6 under the effect of pressure, utilizing density functional theory. The impact of pressure was established in the range of 0–30 GPa. The GGA (generalized gradient approximation) method was performed to figure out exchange correlation effects to determine the ground state geometry of the compounds. A tremendous variation was seen in the lattice parameters, band gap, electronic, optical and transport properties via pressure variation. The Tran and Blaha modified Becke Johnson potential was applied to calculate the electronic band calculations. The energy band gap is observed to shrink from (0.932–0.860) eV and (0.736–0.084) eV for Cs2CuBiBr6 and Cs2CuBiI6 in the studied pressure range. The optical spectra reveal interesting trends upon the application of pressure. Thermoelectric properties were examined by using the BoltzTraP code integrated in Wien2k.