MOLECULAR-DYNAMICS SIMULATIONS OF THE EFFECT OF ADSORPTION ON SIO2 SURFACES

Molecular dynamics computer simulations were used to study the adsorption of model Pt on silica and the effect of this adsorption on the structure of the silica surface. Silica glass and amorphized crystalline surfaces were used as the silica substrates. Results showed a 5-6 angstrom thick adsorbate/substrate interface and an approximately 1 angstrom compression of the substrate surface caused by the presence of the adsorbate film. A significant decrease in the Si-O-Si bond-angle distribution was observed as a result of the adsorption. The shift to smaller bond angles was caused by a distortion of the siloxane bonds in five- and six-membered rings rather than the formation of small sized rings. The smaller bond angles indicate that more reactive sites may exist in the surface.