A MOLECULAR-ORBITAL DERIVED POLARIZATION POTENTIAL FOR LIQUID WATER

A molecular-orbital derived polarization (MP) model is developed and s hown to yield good thermodynamic and structural results for liquid wat er. In this method, each solvent molecule is treated quantum-mechanica lly by the semiempirical AM1 model, and the charge polarization of the molecule is determined by electronic structure calculations, making u se of a hybrid quantum mechanical and molecular mechanical (QM/MM) tec hnique. The MP model is shown to be as successful as the best polariza ble and nonpolarizable three-site potentials for water. In particular, the computed heat of vaporization and density for liquid water at 25 degrees C and 100 degrees C are within 1% of experimental data. In add ition, the MP model gives good estimates for the radial distribution f unctions in comparison with neutron scattering results. (C) 1998 Ameri can Institute of Physics. [S0021-9606(98)51930-7].