Arrays with Local Centers of Symmetry in Space Groups Pca 2 1 and Pna 2 1

Of the several hundred structures in the Cambridge Structural Database [version 4.6 (1992), Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, England] having space groups Pca 2 1 or Pna 2 1 and more than one molecule in the asymmetric unit ( Z > 4), approximately three-quarters co...

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Bibliographic Details
Published in:Acta crystallographica. Section B, Structural science Structural science, 1998-12, Vol.54 (6), p.921-924
Main Authors: Marsh, R. E., Schomaker, V., Herbstein, F. H.
Format: Article
Language:English
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Summary:Of the several hundred structures in the Cambridge Structural Database [version 4.6 (1992), Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, England] having space groups Pca 2 1 or Pna 2 1 and more than one molecule in the asymmetric unit ( Z > 4), approximately three-quarters contain local centers of symmetry. These local centers, which are not crystallographic centers, occur predominantly near x = 1\over8, y = 1\over4 in Pca 2 1 or near x = 1\over8, y = 0 in Pna 2 1 ; this also holds for the limited number of examples we have examined of pseudo-centrosymmetric molecules with Z = 4. Local centers at these points create unusual correlations between corresponding atoms in the two molecules.
ISSN:0108-7681
DOI:10.1107/S0108768198007381