Abstract: The surface geometries of ultrafine silica and its adsorption property for ethanol had been studied by density functional theory using the small cluster model as well as the periodic model. It was found that the method of small cluster model had superiority in some cases, while the periodic model could consider the surface environment of the ultrafine silica in more details. The results indicated that the ethanol molecules were adsorbed on the silica surface mainly through hydrogen bonds, and they favored to act as hydrogen bond acceptors.

Key words: Density functional theory, Period model, Physisorption, Hydrogen bond, Ultrafine silica