The selected 2D monolayer hybrid halide perovskites can therefore maintain their structural integrity at high operation temperatures. Besides RDF and RMSD of the inorganic octahedral framework (MX 4 - 6 ), the dihedral angles of PEA + are also calculated to reveal the interactions between the PEA + groups and the inorganic halide frameworks SnBr 4 - 6 /SnI 4 - 6 . The dihedral and torsion angle of PEA + in the current study (Figure ) is defined by N atoms and benzene rings and by the angle between the plane of the benzene ring and the plane containing N-C-C, respectively. Time-dependent dihedral and torsion angle for PEA + in both 2D monolayer PEA 2 SnBr 4 and PEA 2 SnI 4 oscillate within a narrow range (Figures