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Title: Local structure of Cu in Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate

Abstract

We have used X-ray absorption spectroscopy (XAS) to investigate the local structure of Cu and Ge in the Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate. We show that the local structure parameters for Ge (coordination number and distances) are consistent with those derived on the basis of XRD investigation of Cs{sub 8}Na{sub 16}Ge{sub 136}. The EXAFS data suggest that Cu either randomly substitutes for Ge on the clathrate framework or preferentially on the 96g site but not preferentially on the 32e or 8a sites (Wyckoff notation). Furthermore, we find that the Cu-Ge distance is smaller than the Ge-Ge distance by 0.13 A, indicating a local distortion around the Cu atoms. The estimated degrees of disorder for Cu-Ge and Ge-Ge interactions indicate the Cu-Ge clathrate framework to be relatively stiff, while those for Na-Ge and Cs-Ge interactions corroborate previous observations of strong thermal disorder of the alkali guests in these materials. Our XAS results offer insight into the site substitution of Cu in this material, information unattainable from X-ray diffraction due to the lack of scattering contrast between Cu and Ge. - Graphical abstract: Comparison of Fourier transforms of Cu K-edge and Ge K-edge EXAFS spectra for Cs{sub 8}Na{sub 16}Cu{submore » 5}Ge{sub 131} collected near the temperature of liquid nitrogen (LN). The data clearly show that the Cu-Ge distance is smaller than the Ge-Ge distance, indicating the presence of a local distortion around Cu.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Systems and Materials for Power and Protection Branch, Naval Surface Warfare Center, Carderock Division, West Bethesda, MD 20817-5700 (United States), E-mail: azzam.mansour@navy.mil
  2. Department of Physics, University of South Florida, Tampa, FL 33620 (United States)
  3. Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States)
  4. Department of Physics, University of South Florida, Tampa, FL 33620 (United States), E-mail: gnolas@cas.usf.edu
Publication Date:
OSTI Identifier:
21212164
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 182; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2008.09.024; PII: S0022-4596(08)00488-X; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CESIUM COMPOUNDS; CLATHRATES; COORDINATION NUMBER; COPPER COMPOUNDS; FINE STRUCTURE; GERMANIDES; SODIUM COMPOUNDS; SPECTRA; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY

Citation Formats

Mansour, A.N., Beekman, M., Wong-Ng, W., and Nolas, G.S.. Local structure of Cu in Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate. United States: N. p., 2009. Web. doi:10.1016/j.jssc.2008.09.024.
Mansour, A.N., Beekman, M., Wong-Ng, W., & Nolas, G.S.. Local structure of Cu in Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate. United States. doi:10.1016/j.jssc.2008.09.024.
Mansour, A.N., Beekman, M., Wong-Ng, W., and Nolas, G.S.. Thu . "Local structure of Cu in Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate". United States. doi:10.1016/j.jssc.2008.09.024.
@article{osti_21212164,
title = {Local structure of Cu in Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate},
author = {Mansour, A.N. and Beekman, M. and Wong-Ng, W. and Nolas, G.S.},
abstractNote = {We have used X-ray absorption spectroscopy (XAS) to investigate the local structure of Cu and Ge in the Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} type II clathrate. We show that the local structure parameters for Ge (coordination number and distances) are consistent with those derived on the basis of XRD investigation of Cs{sub 8}Na{sub 16}Ge{sub 136}. The EXAFS data suggest that Cu either randomly substitutes for Ge on the clathrate framework or preferentially on the 96g site but not preferentially on the 32e or 8a sites (Wyckoff notation). Furthermore, we find that the Cu-Ge distance is smaller than the Ge-Ge distance by 0.13 A, indicating a local distortion around the Cu atoms. The estimated degrees of disorder for Cu-Ge and Ge-Ge interactions indicate the Cu-Ge clathrate framework to be relatively stiff, while those for Na-Ge and Cs-Ge interactions corroborate previous observations of strong thermal disorder of the alkali guests in these materials. Our XAS results offer insight into the site substitution of Cu in this material, information unattainable from X-ray diffraction due to the lack of scattering contrast between Cu and Ge. - Graphical abstract: Comparison of Fourier transforms of Cu K-edge and Ge K-edge EXAFS spectra for Cs{sub 8}Na{sub 16}Cu{sub 5}Ge{sub 131} collected near the temperature of liquid nitrogen (LN). The data clearly show that the Cu-Ge distance is smaller than the Ge-Ge distance, indicating the presence of a local distortion around Cu.},
doi = {10.1016/j.jssc.2008.09.024},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 182,
place = {United States},
year = {Thu Jan 15 00:00:00 EST 2009},
month = {Thu Jan 15 00:00:00 EST 2009}
}