QUANTUM CHEMICAL MOLECULAR-MODELS OF OXIDES .3. THE MECHANISM OF WATER INTERACTION WITH THE TERMINAL OH GROUP OF SILICA

New forms for the adsorption of water on the terminal OH group of silica are suggested, with the water interacting with the O3SiOH fragment both as a proton acceptor and as a proton donor simultaneously. The energy preference for these forms with respect to the O3SiOH...OH2 one, proposed in previous quantum chemical studies, is supported by ab initio 6-31G*, 6-31G**//6-31G*, and MP2/6-31G**//6-31G* calculations. The new forms are confirmed also by comparison of their calculated vibrational frequencies with the observed ones for the adsorption complex.