Heat capacity of liquids: A hydrodynamic approach

TL;DR

This study uses molecular dynamics simulations and hydrodynamic theory to analyze the autocorrelation functions of energy, heat, and entropy densities in supercritical argon, enabling the calculation of wavenumber-dependent specific heats that align with experimental data.

Contribution

It demonstrates that hydrodynamic theory accurately predicts entropy density autocorrelation functions and allows for the calculation of wavenumber-dependent specific heats from molecular dynamics simulations.

Findings

Hydrodynamic theory's exponential shape matches MD results at small wave numbers.

Wavenumber-dependent specific heats agree with experimental values in the long-wavelength limit.

The approach provides a method to connect microscopic simulations with macroscopic thermodynamic properties.

Abstract

We study autocorrelation functions of energy, heat and entropy densities obtained by molecular dynamics simulations of supercritical Ar and compare them with the predictions of the hydrodynamic theory. It is shown that the predicted by the hydrodynamic theory single-exponential shape of the entropy density autocorrelation functions is perfectly reproduced for small wave numbers by the molecular dynamics simulations and permits the calculation of the wavenumber-dependent specific heat at constant pressure. The estimated wavenumber-dependent specific heats at constant volume and pressure, $C_{v}(k)$ and $C_{p}(k)$, are shown to be in the long-wavelength limit in good agreement with the macroscopic experimental values of $C_{v}$ and $C_{p}$ for the studied thermodynamic points of supercritical Ar.