Previous experiments have shown that the octahedra within inorganic layer in 2D perovskites exhibit structural distortions in both low and high temperature phases. Such distortion was considered as the displacive characteristic of the phase transition, mixed with the order-disorder transition mechanism. This section focus on analyzing the octahedra distortions obtained from our MD simulation, aiming to uncover the mechanisms governing these distortions. We quantify the distortions using two specific tilting angles: equatorial Pb-I-Pb angle and axial Pb-I-Pb angle, as schematically shown in Figs. and, respectively.