pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2020; 70: 1022-1029

Published online December 31, 2020 https://doi.org/10.3938/NPSM.70.1022

## First-principles Study of Intrinsic Stability of Perovskite Halide MAPbI$_{3}$

Dokyun KIM1, Chul Hong PARK2*

1Department of Physics, Pusan National University, Busan 46241, Korea

2Department of Physics Education, Pusan National University, Busan 46241, Korea

Correspondence to:cpark@pusan.ac.kr

Received: September 28, 2020; Revised: October 29, 2020; Accepted: October 29, 2020

### Abstract

We examined the stability of the MAPbI$_{3}$ perovskite through a first-principles total energy calculation and estimated the thermodynamic energy through phonon calculations. The total energies calculated for the ground state showed that the energy for the dissociation of MAPbI$_{3}$ into MAI and PbI$_{2}$ is small relative to the thermal energy at room temperature, indicating that MAPbI$_{3}$ is not stable for dissociation. We estimated the dependence of the thermodynamics free energies of MAPbI$_{3}$ and MAI and PbI$_{2}$ on the temperature. We found that the entropy effect can contribute to the stabilization of MAPbI$_{3}$, however the stability is not so robust. Because the PbI$_{2}$ has a two-dimensional layered structure, the entropy effect is small compared to that of the three-dimensional structure.

Keywords: Perovskite, Energy material, Stability, Free energy, DFT, Phonon