Entropic elasticity and negative thermal expansion in a simple cubic crystal
Abstract
While most solids expand when heated, some materials show the opposite behavior: negative thermal expansion (NTE). In polymers and biomolecules, NTE originates from the entropic elasticity of an ideal, freely jointed chain. The origin of NTE in solids has been widely believed to be different. Our neutron scattering study of a simple cubic NTE material, ScF₃, overturns this consensus. We observe that the correlation in the positions of the neighboring fluorine atoms rapidly fades on warming, indicating an uncorrelated thermal motion constrained by the rigid Sc-F bonds. This leads us to a quantitative theory of NTE in terms of entropic elasticity of a floppy network crystal, which is in remarkable agreement with experimental results. We thus reveal the formidable universality of the NTE phenomenon in soft and hard matter.
Additional Information
© 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 4 June 2019; Accepted 16 September 2019; Published 1 November 2019. We gratefully acknowledge discussions with C. Li, A. Abanov, and P. Allen. D.W. thanks the Condensed Matter Physics and Materials Science Division at Brookhaven National Laboratory, where part of this work was performed during his summer internship, for the hospitality. Work at Brookhaven National Laboratory (BNL) was supported by the Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract no. DE-SC0012704. Work at BNL's Center for Functional Nanomaterials (CFN) is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy, under the same contract. This research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Author contributions: I.A.Z. conceived and directed the study. I.A.Z., E.B., and B.F. designed the study. B.F. provided the sample for the study. E.B., K.P., and J.N. performed the experiments. E.B. carried out the Rietveld analysis. D.W. and I.A.Z. analyzed the data and prepared the figures. D.W. carried out modeling of the experimental PDF data. L.W. and W.K. performed DFT calculations. A.V.T. and I.A.Z. carried out the theoretical analysis. I.A.Z. wrote the paper, with input from all authors. The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from authors.Attached Files
Published - eaay2748.full.pdf
Supplemental Material - aay2748_SM.pdf
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Additional details
- PMCID
- PMC6824856
- Eprint ID
- 99629
- Resolver ID
- CaltechAUTHORS:20191101-153724236
- DE-SC0012704
- Department of Energy (DOE)
- Created
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2019-11-01Created from EPrint's datestamp field
- Updated
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2022-02-17Created from EPrint's last_modified field