OD STRUCTURES, - GAME AND A BIT MORE

The notion of OD structures consisting of layers is explained, and visualization of its main features facilitated by a simple game: the player is asked to stack prefabricated layers periodic in 2 dimensions, which are all of the same kind or of a small number of different kinds, in accordance with some rules which correspond to the vicinity condition (VC). As shown, important features of the sequences of layers depend only on their symmetry (i.e. layer groups) and on geometrical features of any of the kinds of pairs, especially the layer group of any of the pairs. Table 1 shows that OD crystals consisting of layers occur amongst the most diverse chemical substances. In Tables 2 and 3 some examples of OD crystals with a variety of relations between crystallochemical entities and OD layers are listed. In the Appendix and Table 4 new and simplified formulae for the number Zv'(v) of possible positions of a certain layer Lv′ relative to the fixed position of its predecessor (or successor) Lv are given. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim