DFT-based simulation for the semiconductor behavior of XGeCl₃ (X=K, Rb) halide perovskites under hydrostatic pressure

Abstract In this work, the structural and electronic properties of XGeCl 3 (X=K, Rb) crystallized in cubic cell (Pm-3m, 221) were presented under hydrostatic pressure from 0 to 8 GPa using the first-principal Density Functional Theory (DFT) under the Perdew–Burke–Ernzerhof (PBE) form of the generalized gradient approximation (GGA). The Projector Augmented Wave (PAW) method describing electron–ion interaction was used here. For XGeCl 3 (X=K, Rb), the lattice constants were calculated as 5.171 and 5.197 Å, and the band gaps were predicted as 0.5802 and 0.657 eV, respectively at ambient pressure. It was observed that the lattice parameters and bond lengths of the XGeCl 3 (X=K, Rb) compounds decreased with increased pressure. The applied hydrostatic pressure reduced the band gaps, and the metallic character was detected at 5 GPa for both structures. This study provides a theoretical basis that may have potential uses in optoelectronic applications of the XGeCl 3 (X=K, Rb) perovskites.