In search of invariants for viscous liquids in the density scaling regime: investigations of dynamic and thermodynamic moduli

Abstract

In this paper, we report on nontrivial results of our investigations of dynamic and thermodynamic moduli in search of invariants for viscous liquids in the density scaling regime by using selected supercooled van der Waals liquids as representative materials. Previously, the . Then, we have implemented an idea to transform the definition of the dynamic modulus M p-T from the p-T representation to the V-T one. This idea relied on the disentanglement of combined temperature and density fluctuations involved in isobaric parameters has resulted in finding an invariant for viscous liquids in the density scaling regime, which is the ratio of the thermodynamic and dynamic moduli, B T /M V-T . In this way, we have constituted a characteristic of thermodynamics and molecular dynamics, which remains unchanged in the supercooled liquid state for a given material, the molecular dynamics of which obeys the power density scaling law.2

Breakdown of the Simple Arrhenius Law in the Normal Liquid State

“…7) allows to generate numerically isotherms, isochores and isobars out of measured data as shown in detail in the supplementary information to Ref. [32]. Using this procedure with γ = 4.2 and the Tait EOS from Ref.…”

“…As elaborated in Ref. [32], measured base points are needed for the curve generation. Consequently, isotherms between T = 294 K and 371 K were taken into account based on the underlying data collected at ambient pressure.…”

“…It is worth noting that the scaling criterion (eq ) allows one to numerically generate isotherms, isochores, and isobars out of measured data, as shown in detail in the Supporting Information to ref . Using this procedure with γ = 4.2 and the Tait EOS from ref , τ α ( p ) values were calculated based on the ambient pressure isobar shown in Figure a.…”

“…p infl ( T ) is taken at the minimum of the corresponding V act ( p ) curves, shown in inset (a). As elaborated in ref , measured base points are needed for the curve generation. Consequently, isotherms between T = 294 and 371 K were taken into account based on the underlying data collected at ambient pressure.…”