"Flexible" water molecules in external electrostatic potentials

Effective pairwise potentials for "flexible" water molecules are discussed. It is pointed out that the dependence of the atomic charges on the valence bonds and angle (charge flux) leads to a strong coupling of the inter- and intramolecular coordinates. This coupling significantly modifies the electrostatic forces on the nuclei of the water molecule. It is further pointed out that the contribution of atomic dipoles to the electrostatic forces is comparable to the contribution of the molecular polarizability. Ab initio 6-31G** Hartree-Fock parameters for charge flux and atomic dipoles that can be used in water potentials are suggested.