Quantum effects in liquid water: Path-integral simulations of a flexible and polarizable ab initio model

We examine quantum effects in liquid water at ambient conditions by perform ing path-integral molecular dynamics simulations of a flexible, polarizable water model that was parameterized from ab initio calculations. The quantu m liquid is less structured and has a smaller binding energy, in accord wit h previous simulations. The difference between the quantum and classical li quid binding energies (similar to1.5 kcal/mol) is in reasonable agreement w ith a simple harmonic model, and is somewhat larger than previous estimates in the literature. Quantum effects do not appear to significantly modify t he average induced dipole moment for a polarizable model, although the dist ribution is broader, especially for the component along the C-2 axis of sym metry. (C) 2001 American Institute of Physics.