fig7

Figure 7. ISODISTORT analysis^[46]. The phase transition from tetragonal to cubic, based on the data from Schuck et al.^[6] and Liu et al.^[47] for MAPbI₃ and based on the data from Weadock et al.^[7] for MAPbBr₃ can be described by the temperature-dependent changes of the three degrees of freedom in the tetragonal structure: rotational distortion mode R₄⁺ (blue color, legend on the right) and the two strain mode amplitudes (black color, legend on the left) GM₁⁺ (thermal expansion) and GM₃⁺ (tetragonal distortion (c-a)/c). Fit of the order parameter R₄⁺ for MAPbI₃ based on the data from Schuck et al.^[6] (blue dashed line) and fit for the data from Liu et al.^[47] (blue dotted line), additional also the R₄⁺ fit from Whitfield et al.^[36] (figure 8A in Ref.^[36]) is reproduced (T_c = 329.95 K and β = 0.26, solid blue line). Fit of the order parameter R₄⁺ for MAPbBr₃ based on the data from Weadock et al. (blue dash-dotted line)^[7].