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(d) The h-c notation

In the h-c notation, used by Pauling12, Wyckoff13 and Jagodzinski14, one specifies each layer in terms of the orientation of layers above and below it. A layer is said to be in hexagonal configuration and is denoted as `h` if it is surrounded on either side by layers in similar orientations. A layer is said to be in cubic configuration and is denoted as `c` if it is surrounded on either side by layers in different orientations. Thus the 6H SiC structure with stacking sequence ABCACB can be written as hcchcc in the h-c notation. This notation is specially useful in dealing with X-ray diffraction effects from faulted structures and for calculating stacking fault energies15.


 
Figure 10: RamsdellĘs Zig-Zag sequence of Si (or C) atoms in the (11$\overline{2}$0) plane of 6H (ABCACB).
\begin{figure}
\includegraphics {fig10.ps}
\end{figure}

It is quite easy to transform from one notation to another. For this it is convenient to write first the complete ABC sequence of the structure and then express this in the desired notation. Some close-packed structures expressed in different notations are listed in Table 2.


 
Table 2: Different notations for describing some close-packings
Ramsdell notation ABC sequence Zhdanov number h-c notation
2H AB (11) h
3C ABC ${\infty}$ c
4H ABCB (22) hc
6H 1 ABCACB (33) hcc
6H 2 ABCBAB (2211) hchchh
9R ABACACBCB (12) hhc


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Next: Examples of Some Close-Packed Structures Up: Notations Used for Representing Close-Packed Structures Previous: (c) Zhdanov notation

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