Abstract
The quadrupolar coupling constant Cq and the asymmetry parameter $\ensuremath{\eta}$ for the bridging oxygen sites in vitreous silica structures derived via classical molecular dynamics simulation have been calculated using the point-charge lattice summation method. The results of these calculations indicate that while Cq is a function of both the Si-O-Si angle and the associated Si-O distances, $\ensuremath{\eta}$ depends only on the Si-O-Si angle. The analytical forms of these functional dependences are found to be similar to those reported in previous studies based on ab initio calculations on small clusters. However, the magnitude of Cq is found to decrease with increasing Si-O distance in contrast with a reverse trend obtained in previous ab initio calculations on small clusters. The present results, when combined with the previously reported $^{17}\mathrm{O}$ nuclear magnetic resonance spectroscopic results for bridging oxygen sites in vitreous silica, imply a strong negative correlation between Si-O bond lengths and Si-O-Si bond angles in the glass structure. Such a negative correlation is consistent with the anomalous density variation in silica as well as with energetic considerations.
Published Version
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