ELECTRONIC POLARIZATION OF A WATER MOLECULE IN WATER - A COMBINED QUANTUM-CHEMICAL AND STATISTICAL-MECHANICAL TREATMENT

The polarization of an ab initio quantum chemically described water mo lecule due to the surrounding statistical mechanical Monte Carlo water bath is studied. The quantum chemically described water molecule is s urrounded by 89 statistically described water molecules situated in a spherical cavity in a dielectric continuum. The total interaction betw een the quantum chemically described water molecule and the total surr oundings is on average 0.5 kJ/mol larger than for the interaction for a classically described water molecule. This increase is despite the f act that the potential function used between the quantum chemically de scribed water molecule and a classical water molecule is almost identi cal to the potential between the classical molecules. The difference i s due mainly to the polarization of the quantum chemically and the cla ssically described water molecules.