International
Tables for Crystallography Volume C Mathematical, physical and chemical tables Edited by E. Prince © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. C. ch. 9.2, pp. 752-773
https://doi.org/10.1107/97809553602060000618 Chapter 9.2. Layer stacking |
Footnotes
2 The direction in which there is periodicity is indicated by parentheses (Dornberger-Schiff, 1959).
3 A coincidence operation is a space transformation (called also isometric mapping, isometry, or motion), which preserves distances between any two points of the given object.
4 According to Guinier et al. (1984), triclinic polytypes should be designated A (anorthic) in their Ramsdell symbols.
5 Sandwiches with composition Al(OH)3 (similar to those in CdI2) are the same in both families, but their stacking mode is different. This and similar situations in other substances might have been the reason for distinguishing between `polytype diversity' and `OD diversity' (Zvyagin, 1988).
6 A hexagonally centred unit mesh a1, a2 instead of a primitive mesh A1, A2 is used (Fig. 9.2.2.6b
7 If the symmetry of Tet is P(6)mm (in the Pauling model), Z = 2. This case is common in the literature. However, with the trigonal symmetry of Tet, these two possibilities would correspond to Franzini (1969) types A and B, which are not geometrically equivalent.