A Wyckoff position of a space group G consists of all points X for which the site-symmetry groups are conjugate
Each Wyckoff positon of a space group is labeled by a letter which is called the Wyckoff letter.
The number of different Wyckoff positions of each space group is finite, the
There is a total of 72 Wyckoff
The transfer of Wyckoff positions from individual space groups to space-group types is not unique because Wyckoff positions with the same type of site-symmetry group may be exchanged in different space groups of the same type. This is no longer true when one makes use of Wyckoff sets.
Wyckoff positions of point groups
By analogy to the Wyckoff positions of space groups, Wyckoff positions of point groups have been defined too: here the term "position" indicates the position of face poles (form face
The term Wykcoff position takes its origin from the first English collection of equivalent positions in space groups, which appeared in The analytical expression of the results of the theory of space groups by Ralph W.G. Wyckoff, published by
- Sections 8.3.2 and 10.1.2.2 of the International Tables of Crystallography, Volume A