Symmetry
Symmetry [SYM]
This pull-down menu item allows to specify the symmetry of the 2D crystal sample. For an image of a non-tilted sample, the symmetry can be determined with David Agard's program allspace, using the specific script Get Spacegroup & PhaseOrigin *. This symmetry will be applied during the generation of the symmetrized map, in the specific script *Generate SymMap. An image of a tilted sample has always a p1 symmetry, or no symmetry at all. The symmetry selector can nevertheless be set to the symmetry of the sample, since this does not affect the image processing, which always is done in p1 symmetry. Generation of a symmetrized map does not make sense for a tilted sample. However, having the symmetry set to the correct value might facilitate finding the phase origin for later merging.
Crystal Symmetry, in plane group names, eg p1, p4, p22121.
Note: Some symmetries are not implemented yet– p22121 does not work.
The symmetry operations are applied to the evaluated HKL files (Amplitudes and Phases). The programs in charge of this are located in 2dx/mrc/source and are called symmpp*.cc . If you create a new symmetry operator based on these programs, please provide us with the source, so that we can include it in future versions of 2dx. Alternatively, please let us know if you need a specific symmetry implementation.