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Space group determination: Difference between revisions
start to enumerate space groups that need also to be considered when CORRECT chooses a certain spacegroup
(start to enumerate space groups that need also to be considered when CORRECT chooses a certain spacegroup) |
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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. | ||
== Space group selected by XDS == | == Space group selected by XDS: ambiguous with respect to enantiomorph and screw axes == | ||
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 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, screw axes (see below) are | 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. | ||
For example, if CORRECT suggests 197 (I23) it may as well be 199 (I213); 211 (I432) may as well be 214 (I4132); 75 may in fact be 76, 77, 78. | |||
== Space group selected by user == | == Space group selected by user == | ||