Strong pressure-energy correlations in liquids as a configuration space property: Simulations of temperature down jumps and crystallization

TL;DR

This paper investigates the presence of strong pressure-energy correlations in liquids both at equilibrium and during non-equilibrium processes like aging and crystallization, highlighting their connection to configuration space properties.

Contribution

It demonstrates that strong pressure-energy correlations are inherent to the configuration space and are observable during aging and crystallization in certain liquids.

Findings

Strong correlations observed during aging in certain liquids.

Weak correlations in SPC water during aging.

Crystallization process confirms configuration space property.

Abstract

Computer simulations recently revealed that several liquids exhibit strong correlations between virial and potential energy equilibrium fluctuations in the NVT ensemble [U. R. Pedersen {\it et al.}, Phys. Rev. Lett. {\bf 100}, 015701 (2008)]. In order to investigate whether these correlations are present also far from equilibrium constant-volume aging following a temperature down jump from equilibrium was simulated for two strongly correlating liquids, an asymmetric dumbbell model and Lewis-Wahnstr{\"o}m OTP, as well as for SPC water that is not strongly correlating. For the two strongly correlating liquids virial and potential energy follow each other closely during the aging towards equilibrium. For SPC water, on the other hand, virial and potential energy vary with little correlation as the system ages towards equilibrium. Further proof that strong pressure-energy correlations express a configuration space property comes from monitoring pressure and energy during the crystallization (reported here for the first time) of supercooled Lewis-Wahnstr{\"o}m OTP at constant temperature.