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Abstract

We compare the electrostatic properties of individual water molecules in ab initio simulations and in some potential models used in classical simulations. We find that the standard rigid water models at room temperature and ambient pressure describe the average electrostatic properties of molecules quite well, although there are considerable fluctuations. Preliminary results show that the dipole moment of water molecules near either a sodium ion or a methane molecule are not significantly different from its average value in bulk water, which may justify the use of non-polarisable water models in simulations of biological molecules. In ice, however, the dipole induced by the surroundings is appreciably higher. Incorrect freezing points can be attributed to a bad description of the solid phase rather than to a bad description of the liquid phase. (C) 2002 Elsevier Science B.V. All rights reserved.