Strongly correlating liquids and their isomorphs

Abstract

This paper summarizes the properties of strongly correlating liquids, i.e., liquids with strong correlations between virial and potential energy equilibrium fluctuations at constant volume. We proceed to focus on the experimental predictions for strongly correlating glass-forming liquids. These predictions include i) density scaling, ii) isochronal superposition, iii) that there is a single function from which all frequency-dependent viscoelastic response functions may be calculated, iv) that strongly correlating liquids are approximately single-parameter liquids with close to unity PrigogineDefay ratio, and v) that the fictive temperature initially decreases for an isobaric temperature up jump. The "isomorph filter", which allows one to test for universality of theories for the nonArrhenius temperature dependence of the relaxation time, is also briefly discussed.

Crystallization of the Lewis–Wahnström ortho-terphenyl model

“…13 At sufficient supercooling, we observed an abrupt decrease in the potential energy from a stationary state ( Fig. 13 At sufficient supercooling, we observed an abrupt decrease in the potential energy from a stationary state ( Fig.…”

“…Since its introduction in 1955 by Andrews and Ubbelohde 8 as a useful liquid for the study of the glass transition, the properties of supercooled OTP have been the subject of extensive research. [11][12][13] To the best of our knowledge, crystallization of this model have not been reported before. 10) introduced a model of OTP based on a rigid bent trimer of spherical particles, which has subsequently been used for a number of simulation studies of glassy behavior.…”

Glass Transition Temperature and Density Scaling in Cumene at Very High Pressure

“…It has helped lead to the classification of certain liquids as "strongly correlating" and the development of isomorph theory in which many properties of correlating liquids are invariant under conditions of constant ρ γ /T [22][23][24]. Furthermore, the exponent γ is theorized to provide a critical quantitative connection between cooperative dynamics and the intermolecular potential [20,25,26].…”

Are polar liquids less simple?

“…Dyre and coworkers [2,5] proposed that strong correlation (linear correlation coefficient R  0.9) between equilibrium fluctuations of the virial and potential energy defines a simple liquid. Using this definition they found that associated molecular liquids are not strongly correlating and thus not simple, except at very high densities [2,28].…”