کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
9594222 1507519 2005 5 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The NMR response of boroxol rings: a density functional theory study
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
The NMR response of boroxol rings: a density functional theory study
چکیده انگلیسی
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 5 ppm less than for boron in non-ring BO3/2 units, and that the quadrupole coupling in ring sites is about 0.1 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 134∘ in relaxed structures to 120∘ as found in rings.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Solid State Nuclear Magnetic Resonance - Volume 27, Issues 1–2, January 2005, Pages 5-9
نویسندگان
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