Interaction of H2O clusters with hydrogen-terminated and clean Si(001) surfaces

We performed the LDA first-principles calculations to reveal the water clus ters adsorbed on hydrogenated and clean Si(001) surfaces. In particular the 'wetting' feature is investigated microscopicically. A remarkable finding is the cooperative phenomena of complex water molecules. According to our r esults, the adsorption energy of water molecules on a hydrogenated surface is small on whole parts of the surface, and it shows the well-known hydroph obic character. On the other hand, there are locally strong adsorption site s on a clean surface, and a water cluster is pinned at such sites. An addit ional water molecule connected via a hydrogen bond significantly enhances t he adsorption energy at such a strong adsorption site. (C) 1999 Elsevier Sc ience S.A. All rights reserved.