• Open Access

Pressure dependence of rotational dynamics in barocaloric ammonium sulfate

Bernet E. Meijer, Guanqun Cai, Franz Demmel, Helen C. Walker, and Anthony E. Phillips
Phys. Rev. B 106, 064302 – Published 15 August 2022
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Abstract

Solid-state cooling using barocaloric materials is a promising avenue for ecofriendly, inexpensive, and highly efficient cooling. To design barocaloric compounds ready for deployment, it is essential to understand their thermodynamic behavior under working conditions. To this end, we have studied the rotational dynamics in the molecular-ionic crystal ammonium sulfate under pressure, providing detailed insight into the origin of its large barocaloric effect. Using quasielastic neutron scattering experiments, we show that rotation of the ammonium cations is facilitated by pressure in the low-entropy phase, with the rotational “hopping” motion increasing in frequency as the pressure-induced phase transition is approached. We explain this unusual behavior in terms of the competing hydrogen-bond networks represented by the two phases. This work includes the first results of a recently developed low-background, high-pressure gas cell for neutron scattering, showcasing its power in obtaining high-precision measurements of molecular dynamics under pressure.

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  • Received 27 January 2022
  • Accepted 21 June 2022

DOI:https://doi.org/10.1103/PhysRevB.106.064302

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Bernet E. Meijer1, Guanqun Cai1, Franz Demmel2, Helen C. Walker2, and Anthony E. Phillips1,*

  • 1School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
  • 2ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom

  • *Corresponding author: a.e.phillips@qmul.ac.uk

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Issue

Vol. 106, Iss. 6 — 1 August 2022

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