Effective thermostat induced by coarse-graining of SPC water

TL;DR

This paper explores how a dissipative particle dynamics thermostat influences the transport properties of a coarse-grained SPC water model, showing that the thermostat is integral to the dynamics and can reproduce key properties of detailed water simulations.

Contribution

It introduces an effective thermostat for coarse-grained water models that accurately reproduces diffusion and viscosity by adjusting interactions based on detailed SPC water trajectories.

Findings

The thermostat significantly affects hydrodynamic properties.

Adjusted interactions can replicate SPC water diffusion and viscosity.

Thermostat is integral to coarse-grained dynamics, not just thermal equilibrium.

Abstract

We investigate how the transport properties of a united atoms fluid with a dissipative particle dynamics thermostat depend on the functional form and magnitude of both the conservative and the stochastic interactions. We demonstrate how the thermostat strongly affects the hydrodynamics, especially diffusion, viscosity, and local escape times. As model system we use SPC water, from which projected trajectories are used to determine the effective interactions in the united atoms model. The simulation results support our argument that the thermostat should be viewed as an integral part of the coarse-grained dynamics, rather than a tool for approaching thermal equilibrium. As our main result we show that the united atoms model with the adjusted effective interactions approximately reproduce the diffusion constant and the viscosity of the underlying detailed SPC water model.