Acta Cryst. (2007). B63, 17-25 [ doi:10.1107/S0108768106039462 ]
Abstract: NaxCuO2 (x ![[asymptotically equal to]](/logos/entities/sime_rmgif.gif)
1.6) has been synthesized for different compositions x, resulting in both commensurate and incommensurate composite crystals. The crystal structures are reported for two incommensurate compounds (x = 1.58 and 1.62) determined by Rietveld refinements against X-ray powder diffraction data. The incommensurate compounds and commensurate Na8Cu5O10 (x = 1.6) are found to possess similar structures, with valence fluctuations of Cu2+/Cu3+ as the origin of the modulations of the CuO2 subsystems; the displacive modulations of Na being defined by the closest Na-O contacts between the subsystems. A comparison of the structure models obtained from single-crystal X-ray diffraction, synchrotron-radiation X-ray powder diffraction and X-ray powder diffraction with Cu K![[alpha]](/logos/entities/alpha_rmgif.gif)
1 radiation indicates that single-crystal X-ray diffraction is by far the most accurate method, while powder diffraction with radiation from an X-ray tube provides the least accurate structure model.
Keywords: incommensurate composite crystal; powder diffraction; Rietveld refinement.
 |   Rietveld powder data file (CIF format) (675.7 kbytes) |
| Rietveld powder data file (CIF format) (492.7 kbytes) |
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