On space-group frequencies

In compiling the space-group-frequency table of observed structures, retention of all the 230 space groups is advocated. This is based on some of the fundamental aspects of chirality. For cases both with space-group chirality (case A, e.g. P4₁, P4₃ etc.) and without (case B, e.g. P2₁, P2₁2₁2₁), possible asymmetric distribution of observed structures over mirror equivalents cannot be ruled out. The need to specify a possible physical attribute to characterize a given crystal and correlate this to the absolute structure in case B is pointed out.