Short Space Group Symbol

You clicked on one of the short space-group symbols listed below:

P -1   For triclinic space groups the short and long forms of the space group symbol are identical.
P 21/c
C 2/c
For monoclinic space groups, the short form of the space-group symbol does not indicate which is the unique axis: Although the standard setting for monoclinic space groups is with the unique axis parallel to b, the short space group is not unique when non-standard settings of the unit cell are taken into account. The short form of the space-group symbol should be contrasted with the completely unambiguous full form.
P 21 21 21     For this non-centrosymmetric orthorhombic space group the short and long forms of the space-group symbol are identical. Note that centrosymmetric orthorhombic space groups have both axes and planes, with only the planes being specified in the short form of the space-group symbol.
P n m a   By contrast, centrosymmetric orthorhombic space group, such as the one shown on the left, have both long and short forms. The full form shows the axes, which can be derived from a knowledge of the three planes given in the space group symbol.

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P-1        P21/c        P212121        C2/c       
© Copyright 1995-2006.  Birkbeck College, University of London. Author(s): Jeremy Karl Cockcroft