International
Tables for
Crystallography
Volume G
Definition and exchange of crystallographic data
Edited by S. R. Hall and B. McMahon

International Tables for Crystallography (2006). Vol. G, ch. 3.6, p. 190

Section 3.6.7.6. Crystal symmetry

P. M. D. Fitzgerald,a* J. D. Westbrook,b P. E. Bourne,c B. McMahon,d K. D. Watenpaughe and H. M. Bermanf

aMerck Research Laboratories, Rahway, New Jersey, USA,bProtein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers, The State University of New Jersey, Department of Chemistry and Chemical Biology, 610 Taylor Road, Piscataway, New Jersey, USA,cResearch Collaboratory for Structural Bioinformatics, San Diego Supercomputer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0537, USA,dInternational Union of Crystallography, 5 Abbey Square, Chester CH1 2HU, England,eretired; formerly Structural, Analytical and Medicinal Chemistry, Pharmacia Corporation, Kalamazoo, Michigan, USA, and fProtein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers, The State University of New Jersey, Department of Chemistry and Chemical Biology, 610 Taylor Road, Piscataway, New Jersey, USA
Correspondence e-mail:  paula_fitzgerald@merck.com

3.6.7.6. Crystal symmetry

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The categories describing symmetry are as follows:

SYMMETRY group
 SYMMETRY
 SYMMETRY_EQUIV
 SPACE_GROUP
 SPACE_GROUP_SYMOP

Data items in the SYMMETRY category are used to give details about the crystallographic symmetry. The equivalent positions for the space group are listed using data items in the SYMMETRY_EQUIV category. These categories are used in the same way in the core CIF and mmCIF dictionaries, and Section 3.2.4.4[link] can be consulted for details.

The current version of the mmCIF dictionary includes the SPACE_GROUP categories that were derived from the symmetry CIF dictionary (Chapter 3.8[link] ) and included in version 2.3 of the core CIF dictionary. At the time of writing, macromolecular applications have not yet begun to make use of these new categories.

Data items in these categories are as follows:

(a) SYMMETRY [Scheme scheme179]

(b) SYMMETRY_EQUIV [Scheme scheme180]

(c) SPACE_GROUP [Scheme scheme181]

(d) SPACE_GROUP_SYMOP [Scheme scheme182]

The bullet ([\bullet]) indicates a category key. The arrow ([\rightarrow]) is a reference to a parent data item. Items in italics have aliases in the core CIF dictionary formed by changing the full stop (.) to an underscore (_) except where indicated by the [\sim] symbol.

The data item _symmetry.entry_id has been added to the SYMMETRY category to provide the formal category key required by the DDL2 data model.








































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