On the pressure evolution of dynamic properties of supercooled liquids

Abstract

A pressure counterpart of the Vogel-Fulcher-Tammann (VFT) equation for representing the evolution of dielectric relaxation times or related dynamic properties is discussed:, where P = P − P SL , P 0 is the ideal glass pressure estimation, D P is the pressure fragility strength coefficient, and the prefactor τ P 0 is related to the relaxation time at the stability limit (P SL ) in the negative pressure domain. The discussion is extended to the Avramov model (AvM) relation τ (T,

New Challenges for the Pressure Evolution of the Glass Temperature

“…It is notable that for the basic VFT Eq. 1 the prefactor is "approximately universal, " i.e., τ 0 ≈ 10 −14±2 s, whereas for Eqs 2 and 3, it ranges between τ P 0 ≈ 10s and τ P 0 ≈ 10 −14 s (Drozd- Drozd-Rzoska et al, 2008). Such enormous discrepancy results from the location of the τ(P) isotherm selected for τ(P) or η(P) tests in the respect to T g (P) curve.…”

“…Notwithstanding, the general and model-free forms of E a (T) and V a (P) dependencies are still not known. The solution of the problem of the poorly defined prefactor τ P 0 in Eqs 2 and 3 was proposed in Drozd- and Drozd-Rzoska et al (2008) by introducing the equation:…”

“…5, the prefactor is approximately the same, τ P 0 = τ (P Sp ) ≈ 10 −12 s, for any isotherm. When comparing Eqs 3 and 5 worth noting is that the latter can penetrate negative pressures domain but the fragility strength coefficients changes: Drozd-Rzoska et al, 2008).…”

Dielectric spectroscopy and ultrasonic study of propylene carbonate under ultra-high pressures

“…Upon supercooling and subsequent vitrification, the characteristic frequency of the structural relaxation becomes considerably lower and shifts toward the radio-frequency and even sub-Hertz range. There is a number of works where the pressure dependence of structural relaxation in PC was studied by dielectric spectroscopy methods [10][11][12][13][14] but the data on ultrasound velocity measurements are still absent, although this method not only provides the data on the relaxation characteristics but also sheds the light upon the thermodynamic data, such as the equation of state for the liquid. In the pressure range up to 1.6 GPa, the authors of the Refs.…”

“…As far as we know, there were only a few attempts to study the glass transition by ultrasonic techniques under pressure (e.g., in glycerol 43 ) in contrast to the high-pressure applications of dielectric spectroscopy (see [10][11][12][13][14]19 and references therein) and viscosity measurements (e.g., Refs. 15 and 32 and references therein).…”