Static and Dynamic Disorder in Formamidinium Lead Bromide Single Crystals

We show that formamidinium-based
crystals are distinct from methylammonium-based
halide perovskite crystals because their inorganic sublattice exhibits
intrinsic local static disorder that coexists with a well-defined
average crystal structure. Our study combines terahertz-range Raman
scattering with single-crystal X-ray diffraction and first-principles
calculations to probe the evolution of inorganic sublattice dynamics
with temperature in the range of 10–300 K. The temperature
evolution of the Raman spectra shows that low-temperature, local static
disorder strongly affects the crystal structural dynamics and phase
transitions at higher temperatures.