 The study presents a model for molecular orientation disorder in CH3NH3PBI3, which is a classical Hamiltonian parameterized with electronic structure calculations and a binitio-molecular dynamics. The authors investigate the temperature and electric field dependence of the equilibrium ferroelectric domain structure and resulting polarizability. They observe a rich domain structure of twinned molecular dipoles that varies as a function of temperature and applied electric field. The study proposes that internal electrical fields associated with microscopic polarization domains contribute to hysteretic anomalies in the current voltage response of hybrid organic and organic perovskite solar cells due to variations in electron hole recombination in the bulk. This article was authored by Jarvis Demfrost, Keith T. Butler, and Aaron Walsh.