TOPOLOGICAL AND GEOMETRICAL CHARACTERIZATION OF SITES IN SILICON-CARBIDE POLYTYPES

Sites in SiC polytypes are classified by the numbers of neighbors they have. It is shown that classification by numbers of geometrical neighbors and by numbers of topological neighbors leads to identical results, with the topological description leading to a convenient label for the type of site. The type of site in a layer depends only on the type (h or c) of neighboring layers and not on the type of the layer itself. Ideal coordinates and identification of sites are given for a number of simpler polytypes. A possible application to Si NMR is indicated.