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Largest Likely Values for R factors Calculated After Phase Refinement by Non-crystallographic Symmetry Averaging

Rees, D. C. (1983) Largest Likely Values for R factors Calculated After Phase Refinement by Non-crystallographic Symmetry Averaging. Acta Crystallographica. Section A, Foundations of Crystallography, 39 (6). pp. 916-920. ISSN 0108-7673. doi:10.1107/S010876738300183X.

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The progress of phase refinement by non-crystallographic symmetry averaging is often described by the behavior of a crystallographic R factor expressing agreement between the observed structure factors and structure factors calculated from an averaged electron density map. An upper limit for this R factor is evaluated for the case of incorrectly positioned non-crystallographic symmetry operators. Depending on the degree of non-crystallographic symmetry, the upper limit on R varies from 0.29 to 0.3, for acentric structures. Incorrect structures with the correct non-crystallographic symmetry are anticipated to converge to even lower values of R. In all cases, R values calculated for incorrect structures will be significantly lower than the value of 0.586 characteristic of wrong structures lacking non-crystallographic symmetry [Wilson (1950). Acta Cryst. 3, 397-399].

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Rees, D. C.0000-0003-4073-1185
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Additional Information:© 1983 International Union of Crystallography. Received 22 April 1983; accepted 18 July 1983. This work was supported by a USPHS Biomedical Research Support Grant to UCLA, and a Dreyfus Foundation Starter Grant in Chemistry.
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U.S. Public Health Service (USPHS)UNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Issue or Number:6
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Deposited On:11 Feb 2015 00:10
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