Spin crossover transition driven by pressure: Barocaloric applications

Mario Reis; Yongqiang Cheng; Antonio M. dos Santos

doi:10.1016/j.physb.2024.415689

Spin crossover transition driven by pressure: Barocaloric applications

Mario Reis, Yongqiang Cheng, Antonio M. dos Santos

Research output: Contribution to journal › Article › peer-review

Abstract

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][BF₄]₂. 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.

Original language	English
Article number	415689
Journal	Physica B: Physics of Condensed Matter
Volume	677
DOIs	https://doi.org/10.1016/j.physb.2024.415689
State	Published - Mar 15 2024

Funding

A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The computing resources for DFT calculations were made available through the VirtuES project, funded by Laboratory Directed Research and Development program and Compute and Data Environment for Science (CADES) at ORNL. MSR thanks CNPq and FAPERJ. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The computing resources for DFT calculations were made available through the VirtuES project, funded by Laboratory Directed Research and Development program and Compute and Data Environment for Science (CADES) at ORNL. MSR thanks CNPq and FAPERJ.

Keywords

Barocaloric Effect
Iron metalorganic
Mean Field Modeling
Spin crossover
highpressure

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10.1016/j.physb.2024.415689

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title = "Spin crossover transition driven by pressure: Barocaloric applications",

abstract = "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][BF4]2. 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.",

keywords = "Barocaloric Effect, Iron metalorganic, Mean Field Modeling, Spin crossover, highpressure",

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AU - Cheng, Yongqiang

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N2 - 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][BF4]2. 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.

AB - 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][BF4]2. 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.

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KW - Iron metalorganic

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Spin crossover transition driven by pressure: Barocaloric applications

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