Highly coarse-grained polarisable water models for mesoscopic simulations

TL;DR

This paper introduces a novel coarse-grained polar water model for mesoscopic simulations, enabling better representation of dielectric properties and comparison with atomistic models like TIP3P.

Contribution

It provides a new polar coarse-grained water model and a framework to evaluate its performance against atomistic references.

Findings

The polar model accurately reproduces dielectric properties of water.

Comparison shows the model's effectiveness in simulating electrolytes and membranes.

The approach justifies the coarse-graining level for polar solvents.

Abstract

Modelling micro- and meso-scopic scale thermodynamic and transport properties of soft condensed matter hinges upon its representation. This is especially relevant for polar solvents such as water, since these require effective representation of their dielectric nature as driven by molecular charge distributions and molecular network structuring. The dielectric nature of a medium leads to complex phenomena such as local polarisability response and restructuring near interfaces in reaction to changes in local charge distributions. Inclusion of such phenomena when using larger-than-atomistic techniques such as coarse-grained molecular dynamics (CG-MD) and dissipative particle dynamics (DPD) is still an open question, to which we provide a novel way to consider and justify the necessary and suitable coarse-graining level, enabling us to compare new polar CG models' performance against that of an underlying atomistic model. We polarise our previous non-polar nDPD water model to prepare it for use in simulations of liquid electrolytes as well as solvated organic membranes and measure its fitness to serve as a dielectric medium by comparing its properties to those of the TIP3P water model, while simultaneously observing changes to properties already represented well by the non-polar model.