Strong correlations between equilibrium fluctuations of the configurational parts of pressure and energy are found in the Lennard-Jones liquid and other simple liquids, but not in hydrogen-bonding liquids like methanol and water. The correlations, that are present also in the crystal and glass phases, reflect an effective inverse power-law repulsive potential dominating fluctuations, even at zero and slightly negative pressure. In experimental data for supercritical Argon, the correlations are found to be approximately 96%. Consequences for viscous liquid dynamics are discussed.
@article{arxiv.cond-mat/0702146,
title = {Strong pressure-energy correlations in van der Waals liquids},
author = {Ulf R. Pedersen and Nicholas Bailey and Thomas B. Schrøder and Jeppe C. Dyre},
journal= {arXiv preprint arXiv:cond-mat/0702146},
year = {2009}
}