Abstract
AM1 molecular orbital calculations were conducted for various cluster models of silica and for those of fluorinated silica. Remarkably, the addition of HF to silica clusters gave an F-Si bond forming a trigonal bipyramid geometry around a 5-coordinated Si. The heat of addition reaction of HF was maximum for 4-membered rings and decreased with an increasing number of Si tetrahedra in ring-type silica clusters, while it increased with an increasing number of Si tetrahedra in block-type silica clusters. The addition reaction was strongly dependent on both whether there is sufficient structural flexibility around the Si sites to allow the formation of intramolecular hydrogen bonds with neighbouring silanol groups in the addition of HF and the degree of the strain of the arrangement for [SiO4/2F]-. The heat of reaction for the replacement of one hydroxyl group (OH-) by F- decreased with increasing number of Si tetrahedra. The replacement reaction was strongly dependent on both the size of the rings and the number of bridging oxygens per Si tetrahedron.
| Original language | English |
|---|---|
| Pages (from-to) | 131-140 |
| Number of pages | 10 |
| Journal | Journal of Non-Crystalline Solids |
| Volume | 242 |
| Issue number | 2-3 |
| Publication status | Published - Dec 2 1998 |
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ASJC Scopus subject areas
- Ceramics and Composites
- Electronic, Optical and Magnetic Materials
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Molecular orbital models of silica clusters modified by fluorine. / Hayakawa, Satoshi; Kerch, Larry L.
In: Journal of Non-Crystalline Solids, Vol. 242, No. 2-3, 02.12.1998, p. 131-140.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Molecular orbital models of silica clusters modified by fluorine
AU - Hayakawa, Satoshi
AU - Kerch, Larry L.
PY - 1998/12/2
Y1 - 1998/12/2
N2 - AM1 molecular orbital calculations were conducted for various cluster models of silica and for those of fluorinated silica. Remarkably, the addition of HF to silica clusters gave an F-Si bond forming a trigonal bipyramid geometry around a 5-coordinated Si. The heat of addition reaction of HF was maximum for 4-membered rings and decreased with an increasing number of Si tetrahedra in ring-type silica clusters, while it increased with an increasing number of Si tetrahedra in block-type silica clusters. The addition reaction was strongly dependent on both whether there is sufficient structural flexibility around the Si sites to allow the formation of intramolecular hydrogen bonds with neighbouring silanol groups in the addition of HF and the degree of the strain of the arrangement for [SiO4/2F]-. The heat of reaction for the replacement of one hydroxyl group (OH-) by F- decreased with increasing number of Si tetrahedra. The replacement reaction was strongly dependent on both the size of the rings and the number of bridging oxygens per Si tetrahedron.
AB - AM1 molecular orbital calculations were conducted for various cluster models of silica and for those of fluorinated silica. Remarkably, the addition of HF to silica clusters gave an F-Si bond forming a trigonal bipyramid geometry around a 5-coordinated Si. The heat of addition reaction of HF was maximum for 4-membered rings and decreased with an increasing number of Si tetrahedra in ring-type silica clusters, while it increased with an increasing number of Si tetrahedra in block-type silica clusters. The addition reaction was strongly dependent on both whether there is sufficient structural flexibility around the Si sites to allow the formation of intramolecular hydrogen bonds with neighbouring silanol groups in the addition of HF and the degree of the strain of the arrangement for [SiO4/2F]-. The heat of reaction for the replacement of one hydroxyl group (OH-) by F- decreased with increasing number of Si tetrahedra. The replacement reaction was strongly dependent on both the size of the rings and the number of bridging oxygens per Si tetrahedron.
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M3 - Article
AN - SCOPUS:0032295294
VL - 242
SP - 131
EP - 140
JO - Journal of Non-Crystalline Solids
JF - Journal of Non-Crystalline Solids
SN - 0022-3093
IS - 2-3
ER -