Emergence of a Hump in the Cubic Dielectric Response of Glycerol

TL;DR

This study uses molecular dynamics simulations to analyze the cubic dielectric response of glycerol, revealing a hump associated with collective dynamics that correlates with super-activation and aligns with experimental data.

Contribution

It provides the first direct simulation-based characterization of glycerol's cubic dielectric spectra, linking spectral features to collective effects and dynamical correlations.

Findings

Emergence of a hump in cubic dielectric spectra with supercooling

Hump growth correlates with four-point susceptibility and activation energy

Weak influence of dipolar cross-correlations on spectral shape

Abstract

We report a direct determination of the cubic dielectric spectra of a realistic polar molecule, glycerol, from molecular dynamic (MD) simulations. From the liquid state to the mildly supercooled regime, we observed the emergence and growth of a hump in the cubic modulus, traditionally associated with collective effects in the dynamics. Its evolution follows that of dynamical correlations probed by the four-point susceptibility and that of the activation energy of the relaxation time. In particular, its appearance at high temperature coincides with the onset of super-activation. We show that, for this system, the shape of cubic spectra is only weakly affected by dipolar cross-correlations. The good agreement with experimental observations, despite the difference in temperature range, demonstrates the relevance of this approach to help get an insight into the intricate effects probed by non-linear dielectric spectroscopy.