Commission on Crystallographic Computing

Symmetry in crystallographic applications

Ralf Grosse-Kunstleve
Lawrence Berkeley National Laboratory, CA, USA

A fundamental feature of virtually all crystallographic software is the processing of unit cell parameters and space group operations. In fact, the scope of "crystallography" is often defined by symmetry, in particular periodicity. The "crystallographic unit cell" is our mathematical model for periodicity. The "crystallographic space group" is the model for additional symmetry "inside" the unit cell.

For crystallographic applications, it is often necessary or convenient to transform symmetry information in some way. A simple example is a change-of-basis transformation from a centered cell to a primitive cell. A more complex example is the determination of the search symmetry in structure determination algorithms [1], given a certain crystallographic space group.

In my talk, I will present a general overview of algorithms for the handling of symmetry information. The tutorials will include structured demonstrations of symmetry algorithms available in the Computational Crystallography Toolbox (cctbx). In addition, I will be available to guide students through the process of implementing new algorithms based on the cctbx libraries.

1. Acta Cryst. 2003, D59, 1974-1977

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