Assigning DSC peaks to specific phase transitions in FAPbBr3 beyond the 264 K transition

Identify which structural phase transitions correspond to the additional differential scanning calorimetry peaks observed in formamidinium lead bromide (FAPbBr3) beyond the previously assigned cubic-to-tetragonal transition at 264 K by mapping each DSC feature to a specific symmetry change.

Background

Formamidinium lead bromide (FAPbBr3) exhibits multiple structural transitions upon cooling. While the literature commonly assigns the 264 K DSC feature to a cubic-to-tetragonal (P4/mbm) transition, the identities of the transitions associated with other DSC peaks remain unresolved.

The paper refines space groups at selected temperatures and identifies an Im3 phase at 200 K but explicitly states that the correspondence of other DSC features to specific transitions remains unclear in prior studies.

References

FAPbBr3 undergoes a series of structural phase transitions with decreasing temperature. Consequently, the T = 264 K transition (as seen in Fig. S1 b) has previously been assigned to the cubic-tetragonal transition (tetragonal P4/mbm shown in Fig. S2 b), whereas it remains unclear which individual transitions correspond to the other observed DSC peaks (the orthorhombic Pnma phase depicted in Fig. S2 d was most commonly identified at low temperatures).

— Dynamic Nanodomains Dictate Macroscopic Properties in Lead Halide Perovskites  (2404.14598 - Dubajic et al., 2024) in Supplementary Information, Section i (Phase transitions), paragraph discussing FAPbBr3 DSC (Fig. S1)