Local vibrations and negative thermal expansion in ZrW2O8

We present an x-ray pair distribution function (XPDF) analysis and extended x-ray absorption fine structure (EXAFS) data for ZrW2O8 (10-500 K) with a focus on the stiffness of the Zr-O-W linkage. The XPDF is highly sensitive to W-Zr and W-W correlations, but much less so to O-O or W-O correlations....

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Bibliographic Details
Published inPhysical review letters Vol. 112; no. 4; p. 045505
Main Authors Bridges, F, Keiber, T, Juhas, P, Billinge, S J L, Sutton, L, Wilde, J, Kowach, Glen R
Format Journal Article
LanguageEnglish
Published United States 31.01.2014
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Summary:We present an x-ray pair distribution function (XPDF) analysis and extended x-ray absorption fine structure (EXAFS) data for ZrW2O8 (10-500 K) with a focus on the stiffness of the Zr-O-W linkage. The XPDF is highly sensitive to W-Zr and W-W correlations, but much less so to O-O or W-O correlations. The Zr-W peak in the XPDF data has a weak temperature dependence and, hence, this linkage is relatively stiff and does not permit bending of the Zr-O-W link. We propose that the low energy vibrational modes that lead to negative thermal expansion involve correlated rotations of ZrO6 octahedra that produce large translations of the WO4 tetrahedra, rather than a transverse motion of O atoms that imply a flexible Zr-O-W linkage.
ISSN:1079-7114
DOI:10.1103/PhysRevLett.112.045505