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ID 34000
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Author
Nishimura, Mitsunori
Miura, Yoshinari
Abstract
In Si-29-NMR, it has so far been accepted that the chemical shifts of Q(n) Species (SiO4 units containing n bridging oxygens) were equivalent between alkali borosilicate, and boron-free alkali silicate classes. In the sodium borosilicate glasses with low sodium content. however. a contradiction was confirmed in the estimation of alkali distributions B-11 NMR suggested that Na ions were entirely distributed to berate groups to form BO4 units, whereas a -90 ppm component Was also observed in Si-29-NMR spectra, which has been attributed to Q(3) species associated with a nonbridging oxygen (NBO). Then. cluster molecular orbital calculations were performed to interpret the -90 ppm component in the borosilicate, glasses. It Was found that a silicon atom which had two tetrahedral borons (B4) as its second nearest neighbors was similar in atomic charge and Si2p energy to the Q(3) species in boron-free alkali silicates. Unequal distribution of electrons in Si-O-B4 bridging bonds was also found. where much electrons Were localized oil the Si-O bonds. It was finally concluded that the Si-O-B4 bridges with narrow bond angle were responsible for the -90 ppm Si-29 component in the borosilicate glasses. There still remained another interpretation: the Q(3) species were actually present in the glasses. and NBOs in the Q(3) species were derived from the tricluster groups. such as (O3Si)O(BO3)(2). In the classes With low sodium content. however. it was concluded that the tricluster groups were not so abundant to contribute to the -90 ppm component.
Keywords
short-range order
nuclear-magnetic-resonance
mas-nmr
structural
groups
oxygen sites
ab-initio
o-17 nmr
b-11
na20-b2-3-s1-2
spectroscopy
Note
Digital Object Identifer:doi:10.1016/j.gca.2004.05.042
Published with permission from the copyright holder. This is the author's copy, as published in Geochimica et Cosmochimica Acta, December 2004, Volume 68, Issue 24, Pages 5103-5111.
Publisher URL:http://dx.doi.org/doi:10.1016/j.gca.2004.05.042
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Copyright © 2004 Elsevier Ltd All rights reserved. All rights reserved.
Published Date
2004-12-15
Publication Title
Geochimica et Cosmochimica Acta
Volume
volume68
Issue
issue24
Publisher
Pergamon-Elsevier Science Ltd.
Start Page
5103
End Page
5111
ISSN
0016-7037
NCID
AA00655038
Content Type
Journal Article
language
英語
Copyright Holders
Elsevier Ltd.
File Version
author
Refereed
True
DOI
Web of Sience KeyUT
Submission Path
geology_general/1