Modulated and composite structures dictionary (msCIF) version 1.0.1
The SPACE_GROUP_SYMOP category introduced in the symmetry CIF dictionary (cif_sym.dic) is intended to replace the original core SYMMETRY_EQUIV category. It contains information about the symmetry operations of the space group. For modulated structures, superspace-group descriptions may be included in the same category, but include the _ssg_ flag to indicate their dimensionality of > 3.Example:
Example 1 - example corresponding to the one-dimensional incommensurately
modulated structure of K~2~SeO~4~.
loop_ _space_group_symop_ssg_id _space_group_symop_ssg_operation_algebraic 1 x1,x2,x3,x4 2 1/2+x1,1/2-x2,1/2-x3,x4 3 1/2-x1,1/2+x2,-x3,1/2-x4 4 -x1,-x2,1/2+x3,1/2-x4 5 -x1,-x2,-x3,-x4 6 1/2-x1,1/2+x2,1/2+x3,-x4 7 1/2+x1,1/2-x2,x3,1/2+x4 8 x1,x2,1/2-x3,1/2+x4