Computing absolute free energies of disordered structures by molecular simulation

TL;DR

This paper introduces a Monte Carlo simulation method for directly computing the free energy of disordered systems, applicable to both lattice and off-lattice models, with a focus on challenging off-lattice cases.

Contribution

The paper presents a novel Monte Carlo thermodynamic integration technique using an analytically solvable reference system for disordered structures.

Findings

Effective computation of free energies for off-lattice systems demonstrated

Method successfully applied to hard sphere liquids and hard disk solids with defects

Efficient sampling of thermodynamic paths achieved

Abstract

We present a Monte Carlo simulation technique by which the free energy of disordered systems can be computed directly. It is based on thermodynamic integration. The central idea is to construct an analytically solvable reference system from a configuration which is representative for the state of interest. The method can be applied to lattice models (e.g., the Ising model) as well as off-lattice molecular models. We focus mainly on the more challenging off-lattice case. We propose a Monte Carlo algorithm, by which the thermodynamic integration path can be sampled efficiently. At the examples of the hard sphere liquid and a hard disk solid with a defect we discuss several properties of the approach.