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Density-scaling and the Prigogine–Defay ratio in liquids
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Image of FIG. 1.
FIG. 1.

Reorientational relaxation times for five molecular liquids and local segmental relaxation times for two polymers plotted versus the scaling variable (Eq. (4)). For glycerol the data are limited to T < 290 K due to the large change in behavior at higher temperatures (see text). The solid lines are the best fits of Eq. (6). The quantity plotted is ρ 1/3 T 1/2 times the measured relaxation time (see Ref. 26).

Image of FIG. 2.
FIG. 2.

Representative double logarithmic plots of temperature versus inverse density at constant reduced τ for two materials. The lines represent power law fits (Eq. (5)), with the variation in slope shown in the inset. The average scaling exponents, γ avr , are listed in Table I for each material. For glycerol there is a change in behavior for T > 290 K, which corresponds to pressures exceeding 1.8 GPa.

Image of FIG. 3.
FIG. 3.

(Left) Pearson goodness of fit parameters for Eq. (6) and (right) standard deviation of the power-law exponents (Eq. (5)) divided by the average value versus the inverse square root of the Prigogine–Defay ratio. All data are for atmospheric pressure, except PDE for which P = 120 MPa.

Image of FIG. 4.
FIG. 4.

Ratio of isochoric activation energy and isobaric activation enthalpy versus the inverse square root of the Prigogine–Defay ratio. Higher values of the ordinate correspond to more temperature-driven dynamics.


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Table I.

Scaling exponents and their variation and the Prigogine–Defay ratio.

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Table II.

Activation energy ratio comparison.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Density-scaling and the Prigogine–Defay ratio in liquids