We further evaluated the thermodynamic stabilities of 2D monolayer PEA 2 SnBr 4 and PEA 2 SnI 4 using ab initio molecular dynamics (AIMD) simulations at a working temperature of 350 K. Total energies of both systems (Figure ) fluctuate within a narrow energy range, indicating the structural integrity with no phase transitions even at the extreme operating temperature. Snapshots of 2D monolayer PEA 2 SnBr 4 and PEA 2 SnI 4 (taken every picosecond, Figure ) show that their inorganic framework (e. g. the ordered configuration with networks of corner-sharing octahedrons) are well sustained during the simulations.