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Title: New insights into the negative thermal expansion: Direct experimental evidence for the “guitar-string” effect in cubic ScF 3

The understanding of the negative thermal expansion (NTE) mechanism remains challenging but critical for the development of NTE materials. This study sheds light on NTE of ScF 3, one of the most outstanding materials with NTE. The local dynamics of ScF 3 has been investigated by a combined analysis of synchrotron-based X-ray total scattering, ex-tended X-ray absorption fine structure and neutron powder diffraction. Very interestingly, we observe that i) the Sc-F nearest-neighbor distance strongly expands with increasing temperature while the Sc-Sc next-nearest-neighbor distance contracts, ii) the thermal ellipsoids of relative vibrations be-tween Sc-F nearest-neighbors are highly elongated in the direction perpendicular to the Sc-F bond, indicating that the Sc-F bond is much softer to bend than to stretch, and iii) there is mainly dynamically transverse motion of fluorine atoms, rather than static shifts. Here, these results are the direct experimental evidence for the NTE mechanism, in which the rigid unit is not necessary for the occurrence of NTE, and the key role is played by the transverse thermal vibrations of fluorine atoms through the “guitar-string” effect.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [1] ;  [1] ;  [1]
  1. Univ. of Science and Technology Beijing, Beijing (China)
  2. Univ. of Padova, Padova (Italy)
  3. National Institute of Standards and Technology, Gaithersburg, MD (United States)
  4. Elettra Synchrotron, Triestre (Italy)
  5. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 138; Journal Issue: 27; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
National Natural Science Foundation of China (NNSFC); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1340686

Hu, Lei, Chen, Jun, Sanson, Andrea, Wu, Hui, Rodriguez, Clara Guglieri, Olivi, Luca, Ren, Yang, Fan, Longlong, Deng, Jinxia, and Xing, Xianran. New insights into the negative thermal expansion: Direct experimental evidence for the “guitar-string” effect in cubic ScF3. United States: N. p., Web. doi:10.1021/jacs.6b02370.
Hu, Lei, Chen, Jun, Sanson, Andrea, Wu, Hui, Rodriguez, Clara Guglieri, Olivi, Luca, Ren, Yang, Fan, Longlong, Deng, Jinxia, & Xing, Xianran. New insights into the negative thermal expansion: Direct experimental evidence for the “guitar-string” effect in cubic ScF3. United States. doi:10.1021/jacs.6b02370.
Hu, Lei, Chen, Jun, Sanson, Andrea, Wu, Hui, Rodriguez, Clara Guglieri, Olivi, Luca, Ren, Yang, Fan, Longlong, Deng, Jinxia, and Xing, Xianran. 2016. "New insights into the negative thermal expansion: Direct experimental evidence for the “guitar-string” effect in cubic ScF3". United States. doi:10.1021/jacs.6b02370. https://www.osti.gov/servlets/purl/1340686.
@article{osti_1340686,
title = {New insights into the negative thermal expansion: Direct experimental evidence for the “guitar-string” effect in cubic ScF3},
author = {Hu, Lei and Chen, Jun and Sanson, Andrea and Wu, Hui and Rodriguez, Clara Guglieri and Olivi, Luca and Ren, Yang and Fan, Longlong and Deng, Jinxia and Xing, Xianran},
abstractNote = {The understanding of the negative thermal expansion (NTE) mechanism remains challenging but critical for the development of NTE materials. This study sheds light on NTE of ScF3, one of the most outstanding materials with NTE. The local dynamics of ScF3 has been investigated by a combined analysis of synchrotron-based X-ray total scattering, ex-tended X-ray absorption fine structure and neutron powder diffraction. Very interestingly, we observe that i) the Sc-F nearest-neighbor distance strongly expands with increasing temperature while the Sc-Sc next-nearest-neighbor distance contracts, ii) the thermal ellipsoids of relative vibrations be-tween Sc-F nearest-neighbors are highly elongated in the direction perpendicular to the Sc-F bond, indicating that the Sc-F bond is much softer to bend than to stretch, and iii) there is mainly dynamically transverse motion of fluorine atoms, rather than static shifts. Here, these results are the direct experimental evidence for the NTE mechanism, in which the rigid unit is not necessary for the occurrence of NTE, and the key role is played by the transverse thermal vibrations of fluorine atoms through the “guitar-string” effect.},
doi = {10.1021/jacs.6b02370},
journal = {Journal of the American Chemical Society},
number = 27,
volume = 138,
place = {United States},
year = {2016},
month = {6}
}