The Wyckoff Positions

Additionally, by the use of identification of Wyckoff-position types it is possible to optimize the generation of atomic positions considering their specific local symmetry. In contrast to the DOS version using all symmetry operations in form of the general positions the Windows version uses only the generators selected (see International Tables for Crystallography). Therefore the implemented procedures for the generation of atomic positions of both the DOS and the Windows version are quite different.

The combination of generators produces all symmetry operations. In dependence on the local symmetry, for all special positions specific generators will be combined, respectively. This prevents a multiple generation of special positions and represents the optimized Wyckoff-specific generation of atomic positions. Furthermore, the new data structure of symmetry information in the symmetry file pcwspgr.dat is more compact, because you need in maximum 5 generators in comparision to 48 general positions used for the DOS version. On the one hand this decreases typing errors, on the other hand it is more easy to locate these, because 1/2 or 2/3 of all generated positions must be wrong using the new generation procedure. Additionally, the new symmetry-data structure in pcwspgr.dat simplified its extension by non-conventional settings for orthorhombic and monoclinic space-group types.