SOLID-STATE O-17 MAGIC-ANGLE AND DYNAMIC-ANGLE SPINNING NMR-STUDY OF THE SIO2 POLYMORPH COESITE

Five distinctly resolved O-17 solid-state NMR resonances in room tempe rature coesite, an SiO2 polymorph, have been observed and assigned usi ng dynamic-angle spinning (DAS) at 11.7 T along with magic-angle spinn ing (MAS) spectra at 9.4 and 11.7 T. The O-17 quadrupolar parameters f or each of the five oxygen environments in coesite are correlated with the Si-O-Si bridging bond angles determined by diffraction experiment s. The sign of e(2)qQ/h along with the orientation of the electric fie ld gradient for oxygen in the Si-O-Si linkage were determined from a T ownes-Dailey analysis of the data.