A semiempirical quantum polarization model for water

A semiempirical four-state quantum model for describing the electronic polarizability of water is introduced and implemented in a molecular dynamics simulation. In addition to the phenomenological value of the polarizability, this model introduces another important physical parameter, the mean electronic excitation energy of the individual molecules, which is a useful quantity for discussing the problem of quantum solvation. The implications of the quantum treatment of electronic polarization are investigated for the properties of liquid water. Possible extensions of the model are discussed.