Atomic structure of formamidinium lead iodide perovskite

New perovskite phases containing lead and halogens with a molecular cation are providing new options for materials in solar cells, giving unusually high efficiencies in converting light to electricity. The high-temperature phases of these materials have orientational disorder of the molecular cations. Here we propose an experiment on the new material formamidinium lead iodide, for which disorder in the high-temperature cubic phase has been identified. Our proposal is to perform total scattering measurements from which we can extract the pair distribution function (histogram of interatomic distances), and to analyse the distribution of molecular orientations using the Reverse Monte Carlo method.