First-principles investigations for electronic and thermoelectric properties of XGeF 3 (X = K, Rb): Nonlocal corrections and SCAN insights

In this research work we have studied the electronic band structures, density of states and thermoelectric parameters of fluorine based cubic perovskites KGe F 3 and RbGe F 3 using PW-LDA, PBE-GGA, SCAN, rVV10 and vdW-DF3 exchange correlation functionals implemented in Quantum ESPRESSO for thermoelectric applications. The lattice constant and bulk modulus of KGeF 3 (RbGeF 3 ) is 4.409 (4.407 & Aring;) and 50.8 (51.8 GPa), respectively. KGe F 3 has band gap of 1.917eV and RbGeF 3 has band gap of 1.982eV with PBE. The band structures of both compounds are consistent to total density of states. The Seebeck coefficient, power factor, electrical and thermal conductivity are studied in a wide range of temperature from 0 to 800K. The detailed study of band gaps and thermoelectric parameters with variety of DFT methods indicates the significance of KGe F 3 and RbGe F 3 in thermoelectric devices under high temperature.