Polarizable Atomic Multipole Water Model for Molecular Mechanics Simulation

TLDR

The authors propose a new classical empirical potential for water. The model employs a polarizable atomic multipole framework with multipoles up to quadrupole derived from distributed multipole analysis, self‑consistent induced dipoles damped by a modified Thole scheme, and a buffered 14‑7 van der Waals potential, yielding a fully flexible potential. The potential requires substantial van der Waals parameters on both hydrogen and oxygen, and it shows excellent agreement with experimental and high‑level ab initio data for clusters, liquid water, and ice.

Abstract

A new classical empirical potential is proposed for water. The model uses a polarizable atomic multipole description of electrostatic interactions. Multipoles through the quadrupole are assigned to each atomic center based on a distributed multipole analysis (DMA) derived from large basis set molecular orbital calculations on the water monomer. Polarization is treated via self-consistent induced atomic dipoles. A modified version of Thole's interaction model is used to damp induction at short range. Repulsion−dispersion (vdW) effects are computed from a buffered 14−7 potential. In a departure from most current water potentials, we find that significant vdW parameters are necessary on hydrogen as well as oxygen. The new potential is fully flexible and has been tested versus a variety of experimental data and quantum calculations for small clusters, liquid water, and ice. Overall, excellent agreement with experimental and high level ab initio results is obtained for numerous properties, including cluster st...