Section 1.4.4. Notes on graphical symbols of symmetry planes

(i) The graphical symbols and their explanations (columns 2 and 3) are independent of the projection direction and the labelling of the basis vectors. They are, therefore, applicable to any projection diagram of a space group. The printed symbols of glide planes (column 4), however, may change with a change of the basis vectors, as shown by the following example.

In the rhombohedral space groups (161) and (167), the dotted line refers to a c glide when described with `hexagonal axes' and projected along [001]; for a description with `rhombohedral axes' and projection along [111], the same dotted glide plane would be called n. The dash-dotted n glide in the hexagonal description becomes an a, b or c glide in the rhombohedral description; cf. the first footnote in Section 1.3.1.

(ii) The graphical symbols for glide planes in column 2 are not only used for the glide planes defined in Chapter 1.3 , but also for the further glide planes g which are mentioned in Section 1.3.2 (Note x ) and listed in Table 4.3.2.1 ; they are explained in Sections 2.2.9 and 11.1.2 .

(iii) In monoclinic space groups, the `parallel' glide vector of a glide plane may be along a lattice translation vector which is inclined to the projection plane.

(iv) In 1992, the International Union of Crystallography introduced the `double' glide plane e and the graphical symbol ..--..-- for e glide planes oriented `normal' and `inclined' to the plane of projection (de Wolff et al., 1992); for details of e glide planes see Chapter 1.3 . Note that the graphical symbol for e glide planes oriented `parallel' to the projection plane has already been used in IT (1935) and IT (1952).