1.115: Wyckoff set
A Wyckoff set with respect to a space group G is the set of all points X for which the site-symmetry groups are conjugate subgroups of the normalizer N of G in the group of all affine mappings.
Any Wyckoff position of G is transformed onto itself by all elements of G , but not necessarily by the elements of N . Any Wyckoff set of G is instead transformed onto itself also by those elements of N that are contained in G .