A microscopic refrigeration process triggered through spin-crossover mechanism

We report the giant barocaloric effect determined in a spin-crossover system using a microscopic model. Compared with the widely used gas compression-expansion refrigeration technology, field induced refrigeration in solid materials reduces environmental damages and improves the energy efficiency. The origin of the giant effect was ascribed to the entropic phonon contribution arising from low spin to high spin phase transition, induced by a pressure change. Here, we show that for the applied pressure variation from 1 bar to 4.1 kbar, the isothermal entropy change (ΔST) in a one-dimensional spin crossover system [Fe(hyptrz)3](4-chlorophenylsulfonate)2H2O achieves a maximum value of 55.8 J mol−1 K−1 at 191 K, leading to a huge refrigerant capacity of 2160 J mol−1. Our results were compared with the results of other giant solid refrigerant materials such as (NH4)2SO4, Gd5Si2Ge2, and Gd5[Si0.43Ge0.57]4.