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Published November 1981 | Published
Journal Article Open

The importance of weak reflections in resolving the centrosymmetric-noncentrosymmetric ambiguity: a cautionary tale


The weak diffraction intensities are crucially important in determining whether a crystal structure has a real or only an approximate, center of symmetry; if these intensities are deleted from the data set, an intelligent conclusion may be impossible. In addition, statistical distribution tests, if based only on the stronger intensities, may be strongly biased toward a noncentrosymmetric indication. In one recently published structure determination [Cotton & Fanwick (1980), Acta Cryst. B36, 457-459] a distribution test led to the assignment of the noncentrosymmetric space group Cc to a structure which can be better described and refined in the centrosymmetric space group C2/c.

Additional Information

© 1981 International Union of Crystallography. (Received 7 July 1980; accepted 30 March 1981) Contribution No. 6225 from the Arthur Amos Noyes Laboratory of Chemical Physics. This investigation was supported in part by Public Health Service Grant No. GM 16966 from the National Institute of General Medical Sciences, National Institutes of Health. I am grateful to W. P. Schaefer, V. Schomaker and a referee for helpful suggestions.

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