Fig. 8: Variable-temperature single-crystal structures.
From: Colossal barocaloric effects with ultralow hysteresis in two-dimensional metal–halide perovskites
Conformations of the alkylammonium chains in the LT and HT phases of (a) (DA)2MnCl4 and (b) (NA)2CuBr4, with atomic displacement parameters shown at 50% probability for the C and N atoms of the alkylammonium chains. In the LT phase, decylammonium (DA) chains in (DA)2MnCl4 display one conformation, with a single gauche C–C bond (C2–C3), while nonylammonium (NA) chains in (NA)2CuBr4 adopt two conformations, alternating between chains with a gauche C1–C2 bond (chain A) and those with a gauche C2–C3 bond (chain B). Purple, orange, green, brown, gray, and blue spheres represent Mn, Cu, Cl, Br, C, and N atoms, respectively. H atoms are omitted for clarity. Note that DA chains are disordered over a special position in both the LT and HT phases, while NA chains are modeled with two-part disorder in the LT phase and disordered over a special position in the HT phase. Temperature dependence of Uequiv (equivalent isotropic displacement parameters) is shown for alkylammonium cations in (c) (DA)2MnCl4 and (d) (NA)2CuBr4, at 100 K, 270 K (LT phase), and 330/335 K (HT phase). Error bars represent standard uncertainties.
