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Anharmonic Origin of the Giant Thermal Expansion of NaBr

Shen, Y. and Saunders, C. N. and Bernal, C. M. and Abernathy, D. L. and Manley, M. E. and Fultz, B. (2020) Anharmonic Origin of the Giant Thermal Expansion of NaBr. Physical Review Letters, 125 (8). Art. No. 085504. ISSN 0031-9007. https://resolver.caltech.edu/CaltechAUTHORS:20191111-085942260

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Abstract

All phonons in a single crystal of NaBr are measured by inelastic neutron scattering at temperatures of 10, 300, and 700 K. Even at 300 K, the phonons, especially the longitudinal-optical phonons, show large shifts in frequencies and show large broadenings in energy owing to anharmonicity. Ab initio computations are first performed with the quasiharmonic approximation (QHA) in which the phonon frequencies depend only on V and on T only insofar as it alters V by thermal expansion. This QHA is an unqualified failure for predicting the temperature dependence of phonon frequencies, even 300 K, and the thermal expansion is in error by a factor of 4. Ab initio computations that include both anharmonicity and quasiharmonicity successfully predict both the temperature dependence of phonons and the large thermal expansion of NaBr. The frequencies of longitudinal-optical phonon modes decrease significantly with temperature owing to the real part of the phonon self-energy from explicit anharmonicity originating from the cubic anharmonicity of nearest-neighbor NaBr bonds. Anharmonicity is not a correction to the QHA predictions of thermal expansion and thermal phonon shifts but dominates the behavior.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1103/PhysRevLett.125.085504DOIArticle
https://arxiv.org/abs/1909.03150arXivDiscussion Paper
ORCID:
AuthorORCID
Shen, Y.0000-0001-6838-0925
Saunders, C. N.0000-0001-7973-3722
Bernal, C. M.0000-0001-7550-3153
Abernathy, D. L.0000-0002-3533-003X
Manley, M. E.0000-0003-4053-9986
Fultz, B.0000-0002-6364-8782
Additional Information:© 2020 American Physical Society. Received 31 August 2019; revised 9 June 2020; accepted 24 July 2020; published 21 August 2020. We thank D. Kim, O. Hellman, F. Yang, and J. Lin for helpful discussions. M. E. M. was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division under Award No. DE-AC05-00OR22725. Research with the Spallation Neutron Source at the Oak Ridge National Laboratory was sponsored by the Scientific User Facilities Division, Basic Energy Sciences, of the DOE. This work used resources from National Energy Research Scientific Computing Center, an Office of Science User Facility supported by the Office of Science of the US DOE under Award No. DE-AC02-05CH11231. This work was supported by the DOE Office of Science, Basic Energy Sciences, under Award No. DE-FG02-03ER46055.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC05-00OR22725
Department of Energy (DOE)DE-AC02-05CH11231
Department of Energy (DOE)DE-FG02-03ER46055
Issue or Number:8
Record Number:CaltechAUTHORS:20191111-085942260
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20191111-085942260
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99772
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:12 Nov 2019 21:28
Last Modified:21 Aug 2020 19:55

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