Ab-initio calculation of APbI₃ (A=Li, Na, K, Rb and Cs) perovskite crystal and their lattice constants optimization using density functional theory

Halide perovskite materials APbI₃ (with A is inorganic alkaline cation) have received many attentions in some recent years related to the rapid progress of perovskite solar cells. Particularly, CsPbI₃ perovskite has been much investigated due to relatively more stable in comparison to other inorganic cation while its energy conversion efficiency has reached 10.5%. In this study, we report our calculation results of the geometric structure and the electronic structure of these inorganic perovskites with various alkaline cation. The calculations were performed by employing the Density Functional Theory (DFT) method using Quantum Espresso computational software package. The calculation employed variable-cell relaxation algorithm (vc-relax) to obtain the lowest total energy value and the corresponding Density of States (DOS). In addition, Ultrasoft pseudopotentials and PBE exchange-correlation functions were used. The cut-off of kinetic energy was set at 40 Rydberg and the k-point was set at 5x5x5. The computation results lead to the energy gap range in 1.40 eV to 1.46 eV. In addition, there is also an agreement between the electronic band structures and the DOS distribution pattern for optimum lattice constant.