The Journal of Physical Chemistry B · 1997 · 78 citations · 31 references
Natural SciencesChemistryMaterials SciencePhysical ChemistrySurface ChemistrySurface ScienceMineral Surface ChemistrySurface Chemistry Of SolidsSurface CrystallographySurface EnergeticsSurface PhysicsSurface ReactivityBonding GeometryHydrogen BondingHydrogen Bonding ModelsSilicate ChemistrySiliconSilicon Surface ScienceSpecific OrientationSurface Chemistry 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. 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.
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