Entropy basis for the thermodynamic scaling of the dynamics ofo-terphenyl

Abstract

Structural relaxation times and viscosities for non-associated liquids and polymers are a unique function of the product of temperature, T, times specific volume, V, with the latter raised to a constant, γ τ . Similarly, for both neat o-terphenyl (OTP) and a mixture the entropy for different T and pressures, P, collapse to a single curve when expressed versus S TV γ , with the scaling exponent for the entropy essentially equal to the thermodynamic Grüneisen parameter. Since the entropy includes contributions from motions, such as vibrations and secondary relaxations, which do not affect structural relaxation, γ S < γ τ . We show herein that removal of these contributions gives a satisfactory accounting for the magnitude of γ τ . Moreover, the relaxation times of OTP are found to be uniquely defined by the entropy, after subtraction from the latter of a V-independent component.-submitted to J.

Determination of the Thermodynamic Scaling Exponent for Relaxation in Liquids from Static Ambient-Pressure Quantities

“…These also provide an alternative route to eq.(7). To show this we note that the configurational entropy, C S , conforms to thermodynamic scaling [46,47] (Figure 3) ( ) c S g TV γ = (8) where g is a function, and the scaling exponent is the same γ as in eq.(1). From the continuity of the entropy at the glass transition the derivatives of temperature and volume are related as liquid glass liquid glass…”

Pressure-energy correlations in liquids. III. Statistical mechanics and thermodynamics of liquids with hidden scale invariance

“…40 There have been suggestions of how to connect the socalled density scaling exponent 24,25 -the one controlling the relaxation time via the variable ␥ / T-with the Grüneisen parameter, notably by Roland and co-workers. [41][42][43] In Ref. 41, equality of ␥ G and ␥ was argued theoretically by reference to the Avramov model.…”

Density scaling of the diffusion coefficient at various pressures in viscous liquids

“…On the other hand, following the Avramov entropy model 9 for the structural relaxation time, γ was identified to the thermodynamic Grüneisen parameter G  [10][11][12] . A series of interesting articles reviewing the peculiar properties of glass forming liquids were published recently 1, 2, 4, 13 .…”