Correlated Structural Distributions in Silica Glass

Our 17O Dynamic-Angle Spinning (DAS) result on silica glass is quite significant because it revealed an unexpected result that both the distributions Si-O distance and Si-O-Si in silica glass are considerably narrower than all previous diffraction studies, i.e., revealing a more ordered structure than previously thought. Even more arresting, however, is our finding of a strong positive correlation between Si-O-Si angle and Si-O distance, i.e., Si-O distance decreasing with decreasing Si-O-Si angle.


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This trend would seem counter-intuitive to many in terms of steric effects (local energetics), and also because it runs opposite to trends generally found in crystalline silica polymorphs. On the basis of variable temperature and pressure structural studies of quartz, however, we speculate that this behavior may result from the disequilibrium nature of the glass. Such results will certainly lead to revisions of a number of currently popular structural models, and could provide the impetus to develop new models.



Other References and Related Resources from our Lab


Correlated Structural Distributions in Silica Glass
T. M. Clark, P. J. Grandinetti, P. Florian, and J. F. Stebbins
Dependence of bridging oxygen 17O quadrupolar coupling parameters on Si-O distance and Si-O-Si angle, 

T. M. Clark and P. J. Grandinetti
Text file contain the 17O DAS Spectrum of Silica Glass. Three columns of comma separated values, x/ppm, y/ppm, z/intensity
Text file contains four columns of comma separated values: (1) Quadrupolar Coupling Constant, (2) Quadrupolar Asymmetry Parameter, (3) Isotropic Chemical Shift, and (4) DAS intensity values extracted from each cross-section of the Silica 17O DAS spectrum.
Text file of two columns of comma separated values of the one dimensional histogram of 17O Quadrupolar Coupling Constants in Silica
Text file of two columns of comma separated values of the one dimensional histogram of 17O Quadrupolar Coupling Asymmetry Parameters in Silica
Text file of two columns of comma separated values of the one dimensional histogram of 17O Isotropic Chemical Shift Parameters in Silica
Text file of three columns of comma separated values of the two dimensional histogram of 17O Quadrupolar Coupling Constant and Asymmetry Parameters in Silica
Text file of three columns of comma separated values of the two dimensional histogram of Si-O-Si Angles versus Si-O distance in Silica