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The centrosymmetric–noncentrosymmetric ambiguity: some more examples

Marsh, Richard E. (1994) The centrosymmetric–noncentrosymmetric ambiguity: some more examples. Acta Crystallographica. Section A, Foundations of Crystallography, 50 (4). pp. 450-455. ISSN 0108-7673.

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Four more examples are provided to emphasize the extreme difficulty in deciding, by diffraction methods, whether a crystal structure is centrosymmetric or only approximately so. In these examples, earlier workers described and refined structures in noncentrosymmetric space groups; refinements in the corresponding centrosymmetric space groups, based on the original data, lead to improved results. In one case, apparent violations of systematic absences seem to preclude the centrosymmetric description; however, other evidence - in particular, improved agreement for the very weak reflections (which are the most sensitive to the centrosymmetric non-centrosymmetric ambiguity) - suggest that the space-group violations might be spurious. In any event, the moral is clear: extreme caution is needed when attempting to derive a noncentrosymmetric description of a closely centrosymmetric structure.

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Additional Information:© 1994 International Union of Crystallography. Received 16 June 1992; accepted 17 November 1993.
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Caltech Division of Chemistry and Chemical Engineering8375
Issue or Number:4
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:73626
Deposited By: Tony Diaz
Deposited On:26 Jan 2017 20:43
Last Modified:03 Oct 2019 16:29

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