Estimating the density scaling exponent of viscous liquids from specific heat and bulk modulus data

Abstract

It was recently shown by computer simulations that a large class of liquids exhibits strong correlations in their thermal fluctuations of virial and potential energy [Pedersen et al., Phys. Rev. Lett. 100, 015701 (2008)]. Among organic liquids the class of strongly correlating liquids includes van der Waals liquids, but excludes ionic and hydrogen-bonding liquids. The present note focuses on the density scaling of strongly correlating liquids, i.e., the fact their relaxation time tau at different densities rho and temperatures T collapses to a master curve according to the expression tau propto F(rho^gamma/T) [Schroder et al., arXiv:0803.2199]. We here show how to calculate the exponent gamma from bulk modulus and specific heat data, either measured as functions of frequency in the metastable liquid or extrapolated from the glass and liquid phases to a common temperature (close to the glass transition temperature). Thus an exponent defined from the response to highly nonlinear parameter changes may be determined from linear response measurements.

References in corpus (5)

• Strong pressure-energy correlations in van der Waals liquids
• Hidden scale invariance in molecular van der Waals liquids: A simulation study
• Density scaling as a property of strongly correlating viscous liquids
• Pressure-energy correlations and thermodynamic scaling in viscous Lennard-Jones liquids
• Feasibility of single-order parameter description of equilibrium viscous liquid dynamics