Theoretical investigation of the barocaloric effect in spin-crossover systems upon first- and second-order phase transition conversion

Abstract

We report a theoretical simulation of the barocaloric effect in spin crossover systems starting from a model Hamiltonian, which includes the crystalline electrical field, elastic, and phonon interactions. A systematic study, through the model parameters, allowed the construction of phase diagrams, and the contributions of configurational, magnetic, and phonon entropies for the barocaloric effect were investigated. The majority contribution comes from the phonons (about 76%, in our simulation), which were associated with the large cell volume change during the low-spin-(SL) ↔ high-spin-(HS) phase transition. Besides, the refrigerant capacity due to the barocaloric effect was discussed in the first- and second-order (LS) ↔ (HS) phase transition regimes. We find out that when hysteresis increases, with an increase in pressure, a higher barocaloric effect can be obtained.