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Space group determination: Difference between revisions
→Space group selected by XDS: ambiguous with respect to enantiomorph and screw axes
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In case of a crystal with an unknown space group (SPACE_GROUP_NUMBER=0 in [[XDS.INP]]), XDS (since [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/Release_Notes.html version June 2008]) helps the user in determination of the correct space group, by suggesting possible space groups compatible with the lattice symmetry of the data, and by calculating the R<sub>meas</sub> for these space groups. | In case of a crystal with an unknown space group (SPACE_GROUP_NUMBER=0 in [[XDS.INP]]), XDS (since [http://www.mpimf-heidelberg.mpg.de/~kabsch/xds/html_doc/Release_Notes.html version June 2008]) helps the user in determination of the correct space group, by suggesting possible space groups compatible with the lattice symmetry of the data, and by calculating the R<sub>meas</sub> for these space groups. | ||
XDS (or rather, the CORRECT step) makes an attempt to pick the correct space group automatically: it chooses that space group which has the highest symmetry (thus yielding the lowest number of unique reflections) and still a tolerable R<sub>meas</sub> compared to the R<sub>meas</sub> the data have in any space group (which is most likely a low-symmetry space group - often P1). | XDS (or rather, the [[CORRECT.LP|CORRECT]] step) makes an attempt to pick the correct space group automatically: it chooses that space group which has the highest symmetry (thus yielding the lowest number of unique reflections) and still a tolerable R<sub>meas</sub> compared to the R<sub>meas</sub> the data have in any space group (which is most likely a low-symmetry space group - often P1). | ||
In many cases the automatic choice is the correct one, and re-running the CORRECT step is then not necessary. However, neither the correct enantiomorph nor screw axes (see below) are determined automatically by XDS. | In many cases the automatic choice is the correct one, and re-running the [[CORRECT.LP|CORRECT]] step is then not necessary. However, neither the correct enantiomorph nor screw axes (see below) are determined automatically by XDS. | ||
=== Space groups to consider based on CORRECT suggestion === | === Space groups to consider based on CORRECT suggestion === | ||