A NEW INTERMOLECULAR ENERGY CALCULATION SCHEME - APPLICATIONS TO POTENTIAL SURFACE AND LIQUID PROPERTIES OF WATER

An intermolecular water-water potential including many-body effects has been constructed with a new computational scheme termed NEMO. The total charge distribution and polarizability obtained from ab initio SCF calculations are partitioned into multicenter multipole components. With use of these components, the electrostatic and induction part of the intermolecular interaction energy are estimated. The short-range interaction (mainly exchange repulsion) is calculated from the overlap between the orbitals of the interacting molecules. The dispersion energy is estimated with a London-type approximation. To be able to use these energy estimates in calculating properties of liquids, we fit each contribution to a more computationally convenient expression. Furthermore, in order to be able to use these potentials for simulations at liquid densities, we find it essential to explicitly include many-body polarizability. Molecular dynamics simulations of the polarizable water model reveal structure, energetics, and dynamics compatible with experimental results. Thus the simulation establishes the validity of using our estimated NEMO potential surfaces with polarizabilities for accurate prediction of liquid-state properties. © 1990 American Chemical Society.