Correlation between Local and Long-Range Structure in Compressible Supercritical Lennard-Jones Fluids: State-Point Dependence

Abstract

Evaluation of local-density-specific radial distribution functions in a two-dimensional supercritical Lennard-Jones fluid has enabled us to elucidate how the correlations between a solvent particle's local density and the extended surrounding solvent structure change as a function of the thermodynamic condition. We find that the standard correlation length provides only a very crude measure of these correlations and that, for example, such inhomogeneity-induced correlations remain present at bulk densities surprisingly far from the critical density in this two-dimensional system. Additionally, these local-density-specific radial distribution functions provide insight into the state-point dependence of the origin of mean local-density enhancements, showing that the potential-induced and the correlation-induced contributions both die out rapidly with increasing temperature, whereas they are maximally important at different bulk densities.