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Soft-mode anisotropy in the negative thermal expansion material ReO3

Bird, T.A.; Wilkinson, M.G.L.; Keen, D.A.; Smith, R.I.; Bristowe, N.C.; Dove, M.T.; Phillips, A.E.; Senn, M.S.

Soft-mode anisotropy in the negative thermal expansion material ReO3 Thumbnail


T.A. Bird

M.G.L. Wilkinson

D.A. Keen

R.I. Smith

M.T. Dove

A.E. Phillips

M.S. Senn


We use a symmetry-motivated approach to analyse neutron pair distribution function data to investigate the character of the soft phonon modes in negative thermal expansion (NTE) material ReO3. This analysis shows that its local structure is dominated by an in-phase octahedral tilting mode and that the octahedral units are far less flexible to scissoring type deformations than in the related NTE compound ScF3. The lack of flexibility in ReO3 restricts the NTE-driving phonons to a smaller region of reciprocal space, limiting the magnitude and temperature range of NTE. These results support the idea that structural flexibility is an important factor in NTE materials. Surprisingly, our results show that the local fluctuations, even at elevated temperatures, respect the symmetry and order parameter direction of the initial pressure induced phase transition in ReO3. The result indicates that the dynamic motions associated with rigid unit modes are highly anisotropic in these systems.


Bird, T., Wilkinson, M., Keen, D., Smith, R., Bristowe, N., Dove, M., …Senn, M. (2021). Soft-mode anisotropy in the negative thermal expansion material ReO3. Physical Review B, 104(21), Article 214102.

Journal Article Type Article
Acceptance Date Nov 1, 2021
Online Publication Date Dec 2, 2021
Publication Date 2021-12
Deposit Date Nov 14, 2021
Publicly Available Date Nov 15, 2021
Journal Physical review B: Condensed matter and materials physics
Print ISSN 2469-9950
Electronic ISSN 2469-9969
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 104
Issue 21
Article Number 214102


Accepted Journal Article (2.4 Mb)

Copyright Statement
© 2021 American Physical Society

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