Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9594222 | Solid State Nuclear Magnetic Resonance | 2005 | 5 Pages |
Abstract
Cluster models of boron oxide glasses are studied computationally using density functional theory. It is shown that the isotropic chemical shielding of boron in boroxol rings is about 5Â ppm less than for boron in non-ring BO3/2 units, and that the quadrupole coupling in ring sites is about 0.1Â MHz larger than in non-ring sites, confirming assignments made in glasses and crystalline model compounds. The chemical shielding anisotropy of these sites is computed and shown to be in agreement with recent experimental measurements. Furthermore, it is shown that the reason for the different responses is not the co-planarity of BO3/2 groups bound in rings, but rather the contraction in the B-O-B bond angle from about 134â in relaxed structures to 120â as found in rings.
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Physical Sciences and Engineering
Chemistry
Physical and Theoretical Chemistry
Authors
Josef W. Zwanziger,