Extended x-ray absorption fine structure has been measured at the K edge of copper in CuScO(2) and CuLaO(2) to investigate the local origin of negative thermal expansion (NTE) along the c axis. A positive expansion of the Cu-O bond has been measured within the entire temperature interval to be contrasted with the negative expansion of the distance between average atomic positions measured by diffraction; the inadequacy of the riding correction to diffraction data has been evidenced. The weak temperature dependence of the parallel mean-square relative displacement (MSRD) indicates a rather stiff Cu-O bond, while the large perpendicular MSRD measures an intense relative motion of copper with respect to oxygen atoms perpendicular to the c axis. The comparison between the two compounds enlightens the relevance of the correlation of perpendicular motion to quantitatively explain the apparent NTE of the Cu-O bond.

Negative thermal expansion in crystals with the delafossite structure: An extended x-ray absorption fine structure study of CuScO(2) and CuLaO(2)

Ahmed, Sofia;Dalba, Giuseppe;Fornasini, Paolo;Vaccari, Marco;Rocca, Francesco;Sanson, Andrea;
2009-01-01

Abstract

Extended x-ray absorption fine structure has been measured at the K edge of copper in CuScO(2) and CuLaO(2) to investigate the local origin of negative thermal expansion (NTE) along the c axis. A positive expansion of the Cu-O bond has been measured within the entire temperature interval to be contrasted with the negative expansion of the distance between average atomic positions measured by diffraction; the inadequacy of the riding correction to diffraction data has been evidenced. The weak temperature dependence of the parallel mean-square relative displacement (MSRD) indicates a rather stiff Cu-O bond, while the large perpendicular MSRD measures an intense relative motion of copper with respect to oxygen atoms perpendicular to the c axis. The comparison between the two compounds enlightens the relevance of the correlation of perpendicular motion to quantitatively explain the apparent NTE of the Cu-O bond.
2009
10
Ahmed, Sofia; Dalba, Giuseppe; Fornasini, Paolo; Vaccari, Marco; Rocca, Francesco; Sanson, Andrea; J., Li; A. W., Sleight
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/90745
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