Section 3.1.1.4. Subgroup data

The subgroups are divided into two sections: I Maximal translationengleiche subgroups and II Maximal klassengleiche subgroups. The latter are further subdivided into three blocks:

Loss of centring translations . This block appears only if the space group has a conventionally centred lattice. The centring has been fully or partly lost in the subgroups listed. The size of the conventional unit cell is not changed.

Enlarged unit cell, non-isomorphic . The klassengleiche subgroups listed in this block are non-isomorphic and have conventional unit cells that are enlarged compared with the unit cell of the space group.

Enlarged unit cell, isomorphic . The listing includes the isomorphic subgroups with the smallest possible indices for every kind of cell enlargement. If they exist, index values of 2, 3 and 4 are always given (except for , which is restricted to index 2). If the indices 2, 3 or 4 are not possible, the smallest possible index for the kind of cell enlargement considered is listed. In addition, the infinite series of isomorphic subgroups are given for all possible kinds of cell enlargements. The factor of the cell enlargement corresponds to the index, which is a prime number p, a square of a prime number, or a cube of a prime number (cf. Section 3.1.1.6). If , the specifically listed subgroups with small index values also always belong to the infinite series, so that the corresponding information is given twice in these cases. For this applies only to certain special cases.