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Theoretical Study of Hydroxylated and Dehydroxylated Surfaces of a Cristobalite Model of Silica

The (100) face of β-cristobalite covered by geminal hydroxyls has been taken as a model for the silica surface in order to describe the hydrogen bonding and the condensation of the surface hydroxyls of silica. Periodic Hartree−Fock calculations have been performed for slabs of five atomic layers. Th...

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Bibliographic Details
Published in:The journal of physical chemistry. B 1997-10, Vol.101 (41), p.8197-8203
Main Authors: Vigné-Maeder, F, Sautet, P
Format: Article
Language:English
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Summary:The (100) face of β-cristobalite covered by geminal hydroxyls has been taken as a model for the silica surface in order to describe the hydrogen bonding and the condensation of the surface hydroxyls of silica. Periodic Hartree−Fock calculations have been performed for slabs of five atomic layers. The optimized orientation of the hydroxyls corresponds indeed to hydrogen bonds at the surface. As a result, the surface atoms are slightly more negative and the hydroxyls have a specific orientation:  one pointing outside the surface plane and the other one directed toward the bulk. The H-bond energy is evaluated to 25 kJ·mol-1. The dehydration, leading to siloxane bridges, is endothermic by ≈200 kJ·mol-1. It must be accompanied by a surface restructuring implicating more than only the first silicon and oxygen layers.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp964012b