Spin crossover transition driven by pressure: Barocaloric applications

Journal Article · 15 January 2024 · Physica. B, Condensed Matter

DOI: https://doi.org/10.1016/j.physb.2024.415689 · OSTI ID:2283839

Reis, Mario ^[1]; Cheng, Yongqiang ^[2]; dos Santos, Antonio M.  ^[2]

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1. Universidade Federal Fluminense, Rio de Janiero (Brazil); Universidad de Sevilla (Spain)
2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

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, it was compared with the giant Barocaloric Effect (BCE) of the SCO material [FeL₂][B₄]₂. Furthermore, we found that optical phonons are responsible for 92% of the total barocaloric entropy change. DFT calculations successively indicates that, as expected, the majority of this effect can be traced to low frequencies modes of vibration (400 cm^-1), associated to the Fe coordination.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Compute and Data Environment for Science (CADES)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 2283839
• Journal Information: Physica. B, Condensed Matter, Journal Name: Physica. B, Condensed Matter Vol. 677; ISSN 0921-4526
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English