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Hexagonal and cubic silicon carbide polymorphs give distinctive 29Si and 1% magic angle spinning n.m.r. spectra that can be related to the number of nonequivalent lattice sites in the structure and variations in the non-nearest-neig h bour environment.Silicon carbide exists in many crystalline modifications based on hexagonal a-Sic (wurtzite-type ZnS), and there is also a cubic p-Sic structure (diamond or zinc blende type). The complexity arises from the numerous stacking sequences in the crystal.' A search of the Inorganic Crystal Structure Database2 shows that crystal structures of many polytypes have been determined. They differ in the number of crystallographically nonequivalent silicon and carbon atoms, although the silicon-carbon bond lengths are similar in all the forms. Hence high-resolution solid-state n .m.r. spectroscopy3 has potential for the study of such systems. We now report that 29Si and 13C magic angle spinning n.m.r. (m.a.s. n.m.r.) is highly sensitive to fine points of lattice structure.

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