Spectral shape simplicity of viscous materials

TL;DR

This paper reveals a universal spectral pattern in viscous materials' relaxation behavior, showing that diverse liquids share a mechanically simple relaxation pattern largely unaffected by their structural differences.

Contribution

It uncovers a generic spectral pattern that explains the universality of relaxation strength and stretching in viscous liquids, linking mechanical simplicity to fast reorientation dynamics.

Findings

Viscous liquids exhibit a universal relaxation spectral pattern.

Structural relaxation is insensitive to morphological details.

The pattern explains the universality in dielectric response.

Abstract

A broad survey of viscoelastic data demonstrates that van der Waals, hydrogen-bonded, and ionic liquids, as well as polymeric, inorganic, and metallic melts share a structural relaxation pattern virtually insensitive to their morphological details. This mechanical simplicity is connected with that characterizing the fast reorientation dynamics prevailing in liquids devoid of a distinguishable secondary loss peak. By these means one is able to uncover a generic spectral pattern which rationalizes the recently reported "universality" of relaxation strength vs. stretching of the dielectric response of viscous liquids, significantly broadening the framework in which their relaxation behavior is assessed.