A DFT study of the effect of strain on the structural and electronic properties of perovskite APbBr (A = K, Rb, and Cs).

This study investigated the physical properties of perovskite compounds with the general formula APbBr (A = K, Rb, and Cs), Applying the Density Functional Theory (DFT) method. For these APbBr crystals, the optimum lattice constants are determined, serving as the basis for the computations. In these calculations, pseudopotential by GGA-PBE correlation exchange functional is used. The band gap, Density of States (DOS), Projected Density of States (PDOS), charge density, and charge difference caused by changing the charge of each element in the primary state or the lattice constant in one and three directions are estimated. The energy gaps for KPbBr, RbPbBr, and CsPbBr for GGA-PBE pseudopotentials were 1.7436, 1.7746, and 1.7815 eV and for CsPbBr with optimized and experimental lattice constants, 1.78 eV and 1.81 eV, respectively. Also, computation results showed that in some cases (the size of the lattice constant change, for example, was 10%), there were critical points such as conductivity, topological insulator and n-type semiconductor. Finally, studying the electronic structure of these perovskite by changing the lattice constant is a new and novel method in its own right. Also the electronic structure of this perovskite by changing the lattice constant has not been considered in other studies.