Colossal barocaloric effects in the complex hydride Li ₂ B ₁₂ H ₁₂

Traditional 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 (| 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 | Δ S| ∼ 100 J K^{- 1} kg^{- 1}) in the energy material Li₂B₁₂H₁₂. Specifically, we estimate | Δ S| = 367 J K^{- 1} kg^{- 1} and | Δ T| = 43 K for a small pressure shift of P = 0.1 GPa at 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 reorientational motion at high temperatures.