HIGH-RESOLUTION POWDER DIFFRACTION STUDIES OF COPPER(II) OXIDE

High-resolution powder diffraction coupled with the total-pattern-fitting technique revealed unusual and hitherto unreported diffraction effects for samples of copper(II) oxide. Data were obtained with a conventional diffractometer and strictly monochromatic Cu K-alpha-1 radiation and also with the Daresbury Laboratory synchrotron source (9.1 HRPD). It was found that most lines are skewed, by varying amounts, towards higher or lower angles and there is a small amount of line broadening, which is mainly order dependent. It is shown that the line-profile asymmetry varies systematically throughout reciprocal space and that the magnitude of the effect is sample dependent. No significant peak displacements were detected, but the skewing of lines is consistent with a distribution in the dimensions of the unit cell and hence Cu-O bond lengths.