Simulation of Equilibrated States via Molecular Monte Carlo Method of Systems Connected to 3 Reservoirs

TL;DR

This paper introduces a novel molecular Monte Carlo method connecting systems to three reservoirs (chemical potential, pressure, temperature) to efficiently escape metastable states and achieve equilibrium in complex macromolecular and colloidal systems.

Contribution

The method uniquely adjusts one reservoir based on the Gibbs-Duhem equation and incorporates volume and particle number fluctuations to enhance equilibration.

Findings

Successfully obtained defect-free ordered structures

Facilitated quick equilibration from metastable states

Demonstrated string-like colloidal assemblies

Abstract

Metastable structures in macromolecular and colloidal systems are non-equilibrium states that often have long lifetimes and cause difficulties in simulating equilibrium. In order to escape from the long-lived metastable states, we propose a newly devised method, molecular Monte-Carlo simulation of systems connected to 3 reservoirs: chemical potential $\mu$, pressure $P$, and temperature $T$. One of these reservoirs is adjusted for the thermodynamic equilibrium condition according to Gibbs-Duhem equation, so that this adjusted 3rd reservoir does not thermodynamically affect phases and states. Additional degrees of freedom, i.e. system volume $V$ and the number of particles $N$, reduce kinetic barriers of non-equilibrium states and facilitate quick equilibration. We show globally-anisotropic defect-free ordered structures, e.g. string-like colloidal assembly, are obtained via our method.