Pressure-energy correlations and thermodynamic scaling in viscous Lennard-Jones liquids

TL;DR

This study uses molecular dynamics simulations to show that viscous Lennard-Jones liquids exhibit strong pressure-energy correlations and follow thermodynamic scaling, both linked to an inverse power law approximation of the intermolecular potential.

Contribution

It demonstrates the connection between pressure-energy correlations and thermodynamic scaling in viscous liquids, confirming the role of inverse power law potentials in their dynamics.

Findings

Strong correlation between potential energy and virial in viscous liquids.

Thermodynamic scaling exponent equals the pressure-energy correlation slope.

Correlation strength increases at higher densities.

Abstract

We use molecular dynamics simulation results on viscous binary Lennard-Jones mixtures to examine the correlation between the potential energy and the virial. In accord with a recent proposal [U. R. Pedersen et. al. Phys. Rev. Lett. 100, 015701 (2008)], the fluctuations in the two quantities are found to be strongly correlated, exhibiting a proportionality constant, Gamma, numerically equal to one-third the slope of an inverse power law approximation to the intermolecular potential function. The correlation is stronger at higher densities, where interatomic separations are in the range where the inverse power law approximation is more accurate. These same liquids conform to thermodynamic scaling of their dynamics, with the scaling exponent equal to Gamma. Thus, the properties of strong correlation between energy and pressure and thermodynamic scaling both reflect the ability of an inverse power law representation of the potential to capture interesting features of the dynamics of dense, highly viscous liquids.