Energy Storage using Order-Disorder Phase Transitions in Plastic Crystals

Energy storage materials based on order-disorder phase transitions are a promising strategy for harnessing solar energy in a simple and efficient manner. Thermal energy is stored by inducing a phase transition between an ordered solid phase, where molecules are ordered both translationally and orientationally, and a plastic phase where molecules are allowed to rotate in a more or less free way. Two materials that can be used for this purpose are Neopentyl Glycol (NPG) and methylammonium-lead-iodide (MAPI), the latter having an organic molecule inserted into an inorganic framework, in contrast to the former. From a theoretical perspective, the strategy of harnessing energy through order-disorder transitions requires a deep understanding of the nature of disorder in the plastic phases. This understanding is crucial for analyzing existing materials and developing new ones based on the same principle. In this work, we present Molecular Dynamics simulations aimed at establishing a unified microscopic description that rationalizes the experiments conducted so far. Additionally, the study proposes a standardized protocol for investigating order-disorder phase transitions.