Many widely used molecular models of water are built
from a single
Lennard-Jones site on which three point charges are positioned, one
negative and two positive ones. Models from that class, denoted LJ3PC
here, are computationally efficient, but it is well known that they
cannot represent all relevant properties of water simultaneously with
good accuracy. Despite the importance of the LJ3PC water model class,
its inherent limitations in simultaneously describing different properties
of water have never been studied systematically. This task can only
be solved by multicriteria optimization (MCO). However, due to its
computational cost, applying MCO to molecular models is a formidable
task. We have recently introduced the reduced units method (RUM) to
cope with this problem. In the present work, we apply the RUM in a
hierarchical scheme to optimize LJ3PC water models taking into account
five objectives: the representation of vapor pressure, saturated liquid
density, self-diffusion coefficient, shear viscosity, and relative
permittivity. Of the six parameters of the LJ3PC models, five were
varied; only the H–O–H bond angle, which is usually
chosen based on physical arguments, was kept constant. Our hierarchical
RUM-based approach yields a Pareto set that contains attractive new
water models. Furthermore, the results give an idea of what can be
achieved by molecular modeling of water with models from the LJ3PC
class.