fig4

Figure 4. (A) Averaged Pb-X bond lengths expansion and (B) volumetric expansion of MAPbI₃ (red) and MAPbBr₃ (blue) in the tetragonal (solid symbols) and cubic phase (open and half-open symbols), the phase transformation temperature is indicated in each case (tetragonal to cubic). Besides the data from Schuck et al.^[6] and Weadock et al.^[7], values for the cubic phase of MAPbI₃ are also given from Whitfield et al.^[36] (left half-open symbols) and Stoumpos et al.^[38] (right half-open symbols). (B) In addition to the volume changes for the [PbX₆] octahedra (squares), the volume changes for the total volume (diamond symbols) and the volume changes for the [MAX₁₂] cuboctahedra (circles) are also given. Note: Both Pb-X bond lengths, i.e., the one along tetragonal c (Pb-Xb in Figure 2A) and the one in the tetragonal a-b plane (Pb-Xa in Figure 2A), become smaller in the tetragonal phase with increasing temperature. Both bond lengths (Pb-Xa and Pb-Xb) for MAPbI₃ and MAPbBr₃ are within the error bars of the averaged value Pb-X. Adapted with permission from Schuck et al.^[6]. Copyright 2022 American Chemical Society.