Zincblende structure stacking sequence

Bulk CdS possesses wurtzite structure ( 4 type) or zincblende structure ( 3 type). Both phases are formed by stacking of close-packed planes of cadmium and sulfur atoms. Hexagonal wurtzite structure can be represented as the periodic sequence AB AB AB... of closed-packed planes. Cubic zincblende is a sequence ABCABC... of closed-packed planes. For both structures the tetrahedral surrounding of both elements, cadmium and sulfur, takes place. According to the available literature data X-ray diffraction patterns of nanostructured CdS films and powders synthesized by different methods have similar features. Analysis of these features shows that the atomic structure of CdS nanoparticles differs from that of the bulk material. 

In contrast to this, in the 3-cristobalite structure (S.G. Fd3m) the double tetrahedra are connected in trans-configuration corresponding to the symmetry element 1. This arrangement leads to the layer stacking sequence AB CAB. .. akin to the cubic close-packed (c.c.p.) structure. Figure 3.16b shows the zincblende-type lattice of P-cristobalite with a Si-O distance of 159 pm, an 0-0 distance of 260 pm, a Si-Si distance of 308 pm, and an Si-O-Si angle of 151°. 

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