(Corrections, additions, comments appreciated)
References, methods, programs and source code for Converting Symmetry Operators into a Spacegroup Symbol / Spacegroup NumberDate: Wed, 10 Oct 2001 09:28:36 -0700 (PDT) From: "Ralf W. Grosse-Kunstleve" [[email protected]] To: [email protected] > Can Sginfo take a set of symmetry operators and then > determine the spacegroup? Yes, SgInfo can, but the cctbx is more general. You can try both on the web: http://cci.lbl.gov/servers/cctbx/explore_symmetry.html http://www.csb.yale.edu/user-cgi-bin/sginfo-query Restriction in both cases: - Elements of rotation parts of the symmetry operations must be integers. - Elements of the translation parts must be multiples of some base factor (fixed 1/12 for SgInfo, user-definable for cctbx). Restrictions in SgInfo: - Only the standard lattice translations can be processed (P,A,B,C,I,R,F). - Symmetry operations must be aligned with certain axes. In particular, the primitive setting of some centred space groups cannot be processed. > Are there methods published for doing this? "Algorithms for deriving crystallographic space-group information", R. W. Grosse-Kunstleve Acta Cryst. 1999, A55:383-395 http://journals.iucr.org/a/issues/1999/02/02/au0146/ Ralf
Computational Crystallography Toolbox (CCTBX)
SGInfo (obsolescent - replaced by Computational Crystallography Toolbox (CCTBX)) - Ralf W. Grosse-Kunstleve
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Brute Force method of Converting Symmetry Operators into a Spacegroup Symbol / Spacegroup Number
Date: Fri, 12 Oct 2001 09:39:31 +0100 To: Lachlan Cranswick [[email protected]] From: Louis Farrugia [[email protected]] This functionality is present in SXGRAPH and WinGX. The method used is crude but it works and on any reasonable PC is computed in a second or so, even for the cubic space groups. The algorithm is : a) convert SHELX symmetry operators into the corresponding Seitz matrices and then expand to full set using inversion operators/lattice translations (if present) (b) go through all the Hall symbols in the lookup table of Grosse-Kunstleve and calculate the Seitz matrices using the GETSPEC routines (c) compare with those from (a) until an exact match is found This brute force method was coded first because it's simplest. Searching just a subset of space groups would be easy to implement, but since its so fast I have never bothered.
Ton Spek's Platon also uses a similar technique to WinGX's SXGRAPH - 'selective matching with the relevant subset of the 230 spacegroups and its common variants known to PLATON. One of its applications in PLATON is with respect to ADDSYMPlaton - Ton Spek, Bijvoet Center - Utrecht University
Platon - Ton Spek
The Addsym routine within Platon (for finding extra symmetry in crystal structures) makes use of symmetry operator to spacegroup conversion
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