Correlation between anomalous thermal expansion coefficient and barocaloric effect: Application to spin crossover systems

Abstract We report the strong correlation between anomalous thermal expansion in solid-solid volumetric phase transition and the barocaloric effect. This investigation was carried out in {Fe[H2B(pz)2]2(bipy)} (pz = pyrazolyl; bipy = bipyridine) spin crossover system, in which the spin of Fe2+ changes from sLS = 0 to sHS = 2 coupled with high unit cell volume changes from VLS = 2356 to VHS = 2462 A3, at T1/2–160 K. Giant barocaloric effect, through the isothermal entropy change (ΔST = 60 J kg−1 K−1) upon moderated hydrostatic pressure variation (ΔP = 1 kbar), was indirectly obtained from reported pressure dependence of magnetic susceptibility. Theoretical results, obtained from our microscopic model, updated with the reported metal-ligand asymmetrical stretching z-vibration modes, from DFT calculation, showed a remarkable agreement with the experimental data.