Colossal barocaloric effects in the complex hydride Li$$_{2}$$B$$_{12}$$H$$_{12}$$

Abstract

AbstractTraditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to changes in the applied external fields (i.e., magnetic, electric and/or mechanical stress) and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($$|\Delta T| \sim 1$$ | Δ T | ∼ 1 to 10 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict by using molecular dynamics simulations the existence of colossal barocaloric effects induced by pressure (isothermal entropy changes of $$|\Delta S| \sim 100$$ | Δ S | ∼ 100  J K$$^{-1}$$ - 1 kg$$^{-1}$$ - 1 ) in the energy material Li$$_{2}$$ 2 B$$_{12}$$ 12 H$$_{12}$$ 12 . Specifically, we estimate $$|\Delta S| = 367$$ | Δ S | = 367  J K$$^{-1}$$ - 1 kg$$^{-1}$$ - 1 and $$|\Delta T| = 43$$ | Δ T | = 43  K for a small pressure shift of P = 0.1 GPa at $$T = 480$$ T = 480  K. The disclosed colossal barocaloric effects are originated by a fairly reversible order–disorder phase transformation involving coexistence of Li$$^{+}$$ + diffusion and (BH)$$_{12}^{-2}$$ 12 - 2 reorientational motion at high temperatures.