Ginzburg-Landau free energy for molecular fluids: determination and coarse-graining

TL;DR

This paper develops a method to determine Ginzburg-Landau free energy functions for molecular fluids using extended molecular simulations, enabling better multiscale modeling of critical phenomena.

Contribution

It extends the Wang-Landau method for calculating free energies and provides a coarse-grained free energy parametrization for molecular fluids.

Findings

Successfully determined free energy functions for Ar, CO2, and H2O.

Validated the coarse-grained free energy in modeling criticality.

Parameters are suitable for hybrid atomistic/continuum simulations.

Abstract

Using molecular simulation, we determine Ginzburg-Landau free energy functions for molecular fluids. To this aim, we extend the Expanded Wang-Landau method to calculate the partition functions, number distributions and Landau free energies for $Ar$, $CO_2$ and $H_2O$. We then parametrize a coarse-grained free energy function of the density order parameter and assess the performance of this free energy function on its ability to model the onset of criticality in these systems. The resulting parameters can be readily used in hybrid atomistic/continuum simulations that connect the microscopic and mesoscopic length scales.