Reversible colossal barocaloric effects near room temperature in 1-X-adamantane (X = Cl, Br) plastic crystals

Plastic crystals undergo phase transitions with unusually large volume and entropy changes related to strong molecular orientational disordering. These features have led to a resurgent interest in these ma-terials because recently they have shown great potential in solid-state cooling applications driven by pressure. Here we demonstrate that two plastic crystals derived from adamantane-1-Br-adamantane and 1-Cl-adamantane-undergo colossal reversible barocaloric effects under moderate pressure changes in a wide temperature span near room temperature thanks to a relatively small hysteresis and very high sen-sitivity of the transition temperature to pressure. In particular, 1-Cl-adamantane displays an optimal oper-ational temperature range covering from similar to 40 K below and up to room temperature, and under a pressure change of 1 kbar this compound outperforms any other barocaloric material known so far. Our work gives strong support to plastic crystals as best candidates for barocaloric cooling. We also provide insight into the physical origin of the entropy changes through the analysis of the disorder on the involved phases. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Plastic crystals derived from adamantane exhibit colossal reversible barocaloric effects with high sensitivity to temperature changes under moderate pressures. In particular, 1-Cl-adamantane shows optimal performance over a wide temperature range, surpassing any other known barocaloric material under a pressure change of 1 kbar.