Transport and Helfand moments in the Lennard-Jones fluid. I. Shear viscosity

TL;DR

This paper introduces a Helfand-moment method for calculating shear viscosity in molecular dynamics, demonstrating its accuracy and consistency with traditional methods in Lennard-Jones fluids near the triple point.

Contribution

A novel Helfand-moment approach for shear viscosity calculation that adapts to periodic boundary conditions in molecular dynamics simulations.

Findings

Helfand-moment method yields results in excellent agreement with Green-Kubo.

The method effectively computes shear viscosity in Lennard-Jones fluids.

It provides a new tool for equilibrium molecular dynamics studies.

Abstract

We propose a new method, the Helfand-moment method, to compute the shear viscosity by equilibrium molecular dynamics in periodic systems. In this method, the shear viscosity is written as an Einstein-like relation in terms of the variance of the so-called Helfand moment. This quantity, is modified in order to satisfy systems with periodic boundary conditions usually considered in molecular dynamics. We calculate the shear viscosity in the Lennard-Jones fluid near the triple point thanks to this new technique. We show that the results of the Helfand-moment method are in excellent agreement with the results of the standard Green-Kubo method.