Hydrodynamic anomalies in supercritical fluid

TL;DR

This study uses molecular dynamics simulations to explore hydrodynamic anomalies in supercritical fluids, revealing non-monotonous behaviors of velocity autocorrelation functions and identifying key lines indicating fluid evolution stages.

Contribution

It uncovers the non-monotonous dependence of velocity autocorrelation function amplitudes on temperature and density in supercritical fluids, highlighting hydrodynamic anomalies.

Findings

Identification of maxima lines of VAF asymptote amplitudes in supercritical fluids.

Non-monotonous temperature and density dependence of velocity autocorrelation functions.

Insights into fluid evolution stages into gas based on hydrodynamic anomalies.

Abstract

Using the molecular dynamics simulations we investigate properties of velocity autocorrelation function of Lennard-Jones fluid at long and intermediate time scales in wide ranges of temperature and density. We show that the amplitudes of the leading and subleading VAF time asymptotes, $a_1$ and $a_2$, show essentially non monotonous temperature and density dependence. There are two lines on temperature-density plain corresponding to maxima of $a_1$ ($a_2$) along isochors and isotherms situated in the supercritical fluid (hydrodynamic anomalies). These lines give insight into the stages of the fluid evolution into gas.