Section 4.1.1. Introduction

The synoptic tables of this section comprise two features:

For each crystal system, the text starts with a historical note on the synoptic tables in the earlier editions of International Tables¹ followed by a discussion of points (i) and (ii) above. Finally, those group–subgroup relations (cf. Section 8.3.3 ) are treated that can be recognized from the full and the extended Hermann–Mauguin space-group symbols. This applies mainly to the translationengleiche or t subgroups (type I, cf. Section 2.2.15 ) and to the klassengleiche or k subgroups of type IIa. For the k subgroups of types IIb and IIc, inspection of the synoptic Table 4.3.2.1 provides easy recognition of only those subgroups which originate from the decentring of certain multiple cells: C or F in the tetragonal system (Section 4.3.4 ), R and H in the trigonal and hexagonal systems (Section 4.3.5 ).