Centrosymmetric crystal structures described as non-centrosymmetric: An analysis of reports in Inorganica Chimica Acta

A full set of centrosymmetric crystal structures published in Inorganica Chimica Acta as being non-centrosymmetric has been examined. Many have origin-free directions in the non-centrosymmetric description. Frequently insufficient data have been measured. Values obtained for the Flack parameter have been analyzed. With sufficient data coverage, a value close to 0.5 is obtained. With insufficient data a value near to zero has been observed and explained. Many of these structures qualify for the ORTEP-of-the-Year prize.

The diagram shows the crystal structure of MIRLEE refined as non-centrosymmetric but really centrosymmetric. The missed symmetry elements are indicated in red. This centrosymmetric structure is one of several showing a value of the Flack parameter typical of an untwinned non-centrosymmetric crystal structure. This surprising result is due to inadequacies in data-measurement, structure-solution and refinement procedures.Figure optionsDownload as PowerPoint slide