Molecular orbital calculation of the Si NMR chemical shift in borosilicates: The effect of boron coordination to SiO4 units

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Abstract

Borosilicate cluster models were constructed, and the 29Si NMR chemical shift was estimated by molecular orbital calculations. For Q 4 species (an SiO4 unit consisting of four bridging oxygen atoms), a higher frequency shift was confirmed due to the replacement of the surrounding SiO4 with BO4 units, and for Q4 species associated with more than one BO4 unit, the chemical shifts were nearly identical to those for Q3 species (an SiO4 unit including one nonbridging oxygen) in alkali silicates. The chemical shifts of Q4 species in borosilicates were interpreted in terms of the change in bond angle of Si-O-(Si,B4) bridges. A change in chemical shift anisotropy of Q4 species was also found. The Q4 species associated with two BO4 units indicated an anisotropy maximum, which was smaller than the anisotropy of Q3 species.

Original languageEnglish
Pages (from-to)301-304
Number of pages4
JournalPhysics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B
Volume50
Issue number5
Publication statusPublished - Oct 2009

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Materials Chemistry
  • Physical and Theoretical Chemistry
  • Condensed Matter Physics

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