Zhdanov symbols

State the Jagondzinski and the Zhdanov symbols for the closest-packings of spheres with the following stacking sequences ... 

Zhdanov or Jagodzinski symbol). The most important structure types of this kind are the following (M atoms dark gray in the figures positions of M atoms in the following layer marked by black circles) ... 

Another common notation for describing stacking of close-packed 36 nets (T nets) is that devised by Zhdanov (1945) (a number notation equivalent to Jagodzinski s notation). A short description of the Zhdanov symbol is the following a + is assigned if the order between a layer and its previous partner follows the... 

Figure 8.9 Simplified representations of polytypes (a) wurtzite, 2H, (11) (b) carborundum I, AH, (22) (c) 6H, (33). The zig-zag designs to the right of the structure representations show the sequence of translations in a direction, + or —, summarised in the Zhdanov symbol. In the zig-zags, each circle represents the position of a composite (Zn + S) or (Si + C) layer...

The Zhdanov notation specifies the stacking sequence in yet another way. The translation between an A layer and a B layer or a B layer and a C layer can be represented by a rotation of +60° or a translation of + K. Reverse transformations, C to B or B to A, are then represented by -60° or The stacking sequence of any polytype can then be written as a series of + and - signs. This, itself, does not result in a compact notation, and this is addressed by the Zhdanov symbol of the poly type, which gives the number of signs of the same type in the sequence. Thus the cubic... 

C—SrTiO, perovskite stmcture has a stacking sequence symbol is written as (1) rather than ( ). The hexagonal 2H—BaNiOj stmcture has a stacking sequence +-+- so the Zhdanov symbol is (11). Similarly, the high-... 

Zhdanov symbol (22). Zhdanov symbols are particularly useful when depicting very long, complex polytypes, such as those found in the ZnS and SiC systems, but are less frequently encountered in descriptions of hexagonal perovskites. 

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