Adsorption of water on chlorine-terminated Si(111) from first principles: Substrate-induced ordering versus intermolecular interactions

The adsorption of water molecules on a chlorine terminated Si(111) substrate is used as a model to analyze in detail the interaction between water and a hydrophilic surface by means of first-principles calculations. Possible initial adsorption configurations for single water molecules and the potential energy surface are studied. The water monomers are found to adsorb preferably on interstitial sites between surface chlorine atoms. The effect of the substrate on the rotational orientation of the molecule is very small. This is consistent with the computational results for a full termination layer of water on the surface which show that the long-range order of the water layer stems from intermolecular interactions rather than from substrate-induced ordering effects.