GENERAL - Space group symbols

1.6 - Space group symbols in the WinGX system

The short Herman-Mauguin symbols as described in International Tables Vol A. are used. The space-group interpreter routine used by WinGX is quite flexible and general. All non-standard settings are acceptable, but centrosymmetric space groups must have the origin coinciding with an inversion centre.

The input space group symbol is first checked against the look-up table SGINFO.DAT. If no match is found, an error message to this effect is issued. The Herman-Mauguin symbol is then converted to the Hall symbol, and the symmetry matrices derived from this using the GETSPEC routines of Brown and coworkers.

The character string for the input symbol is case-insensitive. The SHELXTL syntax for subscripts may be used, but is unnecessary. Example syntax is:

P21/C    P2(1)/c   P 1 21/c 1  P1121   cmm2    I 4/m m m   P 32 2 1  R-3:h

The last example show how you may explicitly specify the setting, for those cases where International Tables allows more then one setting. In this example the space group R-3 on hexagonal axes is indicated. For more details of the conventions used for various settings, see here

WinGX uses the Hall symbol internally, since this is an unambiguous indicator of space group type.