This article describes a mean-field theoretical model for Spin-Crossover (SCO) materials and explores its implications. It is based on a simple Hamiltonian that yields the high spin molar fraction as a function of temperature and pressure, as well as a temperature-pressure phase diagram for the SCO transition. In order to test the model, we apply it to the giant Barocaloric Effect (BCE) of the SCO material [FeL2][BF4]2 and comprehensively analyse its behavior. We found that optical phonons are responsible for 92\% of the total barocaloric entropy change. DFT calculations show that these optical phonons are mainly assigned to the low frequencies modes of vibration (<400 cm−1), being associated to the Fe coordination.
Cite
@article{arxiv.2304.05353,
title = {Spin crossover transition driven by pressure: Barocaloric applications},
author = {Mario Reis and Yongqiang Cheng and Antonio M. dos Santos},
journal= {arXiv preprint arXiv:2304.05353},
year = {2023}
}