On some experiences with the thr notation for CdI₂ polytypes

Abstract

The advantages of the thr notation are discussed using 12 recently reported polytypes as exaiiiples. It is shown t h a t the thr notation combines the advantages of the Zhdanov notation with those of the t-ci-f notation. An almost trivial conversion of Zhdanov sequences i r i t o thr scqucnurs and vice versa is given. The restrictions in the stacking of CdI, polytypes uircl the relations lwtween liwiioiiretrir struoturrs OUII be described in the lnost simple way using the tlir notation.Die Vorteile der thi-Syi~ibole werden am Beispiel von 12 kiirzliuh veriiffeiitliohten Polytypen diskutiert. Es wird gezeigt, da8 die thr Syinbole die Vorteile der Zhdanov-und der t-o-f-Symhole in sich vereinen. Es wird eine nahezu triviale Methode angegeben, wie Zhdanov-Syrnbole untl thr-Symbole ineinander transformiert werden konnen. Die Besohriinkungen fur die Stapelrnoglichkeiten in CdI,-Polytypen und die Beziehungen zwi-sc~lien ~ioriioiiietrisclieri Stnikturen konnen a111 einfttchsten foririuliert werden, wenn man die tlir-Sy~ribole benutAt.

Generalizations of the hc notation

“…For such a description, notations have already been introduced by Palosz and Przedmojski (1980), Palosz, (1980) and Fichtner (1982. Fichtner (1983Fichtner ( , 1984 has proposed a notation that is based on pairs of sandwiches and may be regarded as a generalization of the he notation. If in Cdl 2 a certain sandwich is fixed, for the adjacent sandwich four possibilities are in agreement with a close-packing of anion layers (Fig.…”

Homometric polytypes in cadmium iodide

“…The condition that the origins of all layers are on a straight line means that there is a straight line through cadmium ions of all boundary sandwiches between two successive S or T layers. For the construction of suitable examples, the thr notation (Fichtner, 1984(Fichtner, , 1983) is used. This notation describes any CdI2 polytype as a sequence of pairs of neighbouring sandwiches (Fig.…”

Molecular and crystal structure of C.I. Pigment Yellow 1. 11680, N-PhenyI-2-(4-methyl-2-nitro-phenylhydrazono)- 3-oxo-butyramide (Hansagelb G)

“…Thus, the normal ABC notation, the he notation as well as the Zhdanov notation may be used (compare Verma and Krishna, 1966). Fichtner (1983Fichtner ( , 1984 has proposed a notation that is based on pairs of sandwiches and may be regarded as a generalization of the he notation. 9.…”