Isomorph theory prediction for the dielectric loss variation along an isochrone

Abstract

This paper derives a prediction for the variation of the amplitude of the dielectric loss from isomorph theory, and presents an experimental test of the prediction performed by measuring the dielectric-relaxation behavior of the van der Waals liquid 5-phenyl-4-ether (5PPE). The liquid is studied at isochronal states in the temperature range $266-333$ K and pressure range $0.1-300$ MPa, for relaxation times around $10^{-3}$ s and $10^{-4}$ s. From the isomorph statement that there is structural and dynamic invariance of isomorph states in reduced units for Roskilde simple liquids we derive four equivalent isomorph-invariant terms, one of which is used in analyzing our data. It is the frequency-dependent term ${\chi }_e(f){\rho }^{\gamma -1}$, with electric susceptibility ${\chi }_e$, density $\rho$, and density-scaling factor $\gamma$. Due to the unique design of our experimental setup, we obtain dielectric loss data where the amplitude is reproducible $\pm 0.1\%$. We moreover find that the empty capacitance of the capacitor cell is stable within $\pm 0.3\%$ in our measuring range and can be assumed to be constant. Using this we predict for two isomorph states there is $-C_2"(f)=-C_1"(f){\left({\rho }_1/{\rho }_2\right)}^{\gamma -1}$ to scale the negative imaginary capacitance, where $C_1$ is the capacitance measurement at ambient pressure and $C_2$ is the predicted capacitance at elevated pressure. We visually compare the predicted and measured plots and there is good match between the two plots among the 42 pairs of isochronal states from the measurement.

References in corpus (3)

• Pressure-energy correlations in liquids. I. Results from computer simulations
• Pressure-energy correlations in liquids. II. Analysis and consequences
• Estimating the density-scaling exponent of a monatomic liquid from its pair potential

Cited by in corpus (17)

• Freezing and melting line invariants of the Lennard-Jones system
• Approximate scale invariance in particle systems: a large-dimensional justification
• Mechanical disorder of sticky-sphere glasses. I. Effect of attractive interactions
• Impact of size polydispersity on the nature of Lennard-Jones liquids
• Effect of Energy Polydispersity on the Nature of Lennard-Jones Liquids
• Studies of the Lennard-Jones fluid in 2, 3, and 4 dimensions highlight the need for a liquid-state 1/d expansion
• Generalized single-parameter aging tests and their application to glycerol
• Connection between fragility, mean-squared displacement and shear modulus in two van der Waals bonded glass-forming liquids
• The EXP pair-potential system. I. Fluid phase isotherms, isochores, and quasiuniversality
• Isomorph theory of physical aging
• Isomorph theory beyond thermal equilibrium
• High pressure specific heat spectroscopy reveals simple relaxation behavior of glass forming molecular liquid
• Scaling properties of liquid dynamics predicted from a single configuration: Small rigid molecules
• A pair potential that reproduces the shape of isochrones in molecular liquids
• Generalized hydrodynamics of the Lennard-Jones liquid in view of hidden scale invariance
• Scaling Properties of Liquid Dynamics Predicted from a Single Configuration: Pseudoisomorphs for Harmonic-Bonded Molecules
• Isomorphs in nanoconfined liquids