Prediction of isochoric heat capacity: Discrete versus continuous potentials

Abstract

Prediction of derivative properties, such as the isochoric heat capacity, remains a real challenge for equations of state. Molecular-based equations of state are derived through a set of approximations, e. g., perturbation theory. The subtleness of these approximations, inaccessible to such a macroscopic description, might be tested with molecular simulations via top-down approaches, where the model parameters used in the molecular simulations are taken from a molecular-based equation of state. In this study, we have calculated the isochoric heat capacity of carbon dioxide comparing three different equations of state based on perturbation theory and two different force fields derived from two of the equations of state. The effects of different potentials (discrete and continuous potentials) and the approximations taken in the derivation of the equations of state were thoroughly analyzed. No model was able to accurately predict heat capacity, but the ones using continuous potentials provided the best results.