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

TL;DR

This paper predicts colossal barocaloric effects in Li$_{2}$B$_{12}$H$_{12}$, with large entropy and temperature changes under moderate pressure, offering a promising solid-state cooling material with reversible phase transition properties.

Contribution

It introduces the prediction of giant barocaloric effects in a complex hydride, supported by molecular dynamics simulations, highlighting its potential for environmentally friendly refrigeration.

Findings

Isothermal entropy change of 387 JK$^{-1}$kg$^{-1}$ at 475 K

Temperature change of 26 K under 0.4 GPa pressure

Reversible phase transition involving Li$^{+}$ diffusion and reorientational motion

Abstract

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 external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($|\Delta T| \sim 1$ K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of $|\Delta S| \sim 100$ JK$^{-1}$kg$^{-1}$) in the energy material Li$_{2}$B$_{12}$H$_{12}$ by means of molecular dynamics simulations. Specifically, we estimate $|\Delta S| = 387$ JK$^{-1}$kg$^{-1}$ and $|\Delta T| = 26$ K for an applied pressure of $P = 0.4$ GPa at $T = 475$ K. The disclosed colossal barocaloric effects are originated by an order-disorder phase transformation that exhibits a fair degree of reversibility and involves coexisting Li$^{+}$ diffusion and (BH)$_{12}^{-2}$ reorientational motion at high temperatures.