Johari-Goldstein Relaxation Events Are Metabasin Transitions

TL;DR

This paper demonstrates that Johari-Goldstein relaxation events in propylene carbonate are actually transitions between metabasins on a potential energy landscape, revealed through neutron scattering analysis.

Contribution

It introduces a heterogeneous model to interpret neutron scattering data, linking $eta_{JG}$ relaxation to metabasin transitions in a molecular glass former.

Findings

Identification of two dynamic signatures beyond diffusion.

Confirmation that $eta_{JG}$ relaxation corresponds to metabasin transitions.

Analysis of q-dependence supports the metabasin transition interpretation.

Abstract

We show that by representing quasi-elastic and inelastic neutron scattering from propylene carbonate (PC) with an explicitly heterogeneous model, we recover two distinct dynamic signatures in addition to diffusive motion. The intermediate scattering function provides access to the time-dependence of these two dynamic processes, and they appear to correspond to transitions between inherent states and between metabasins on a potential energy landscape. By fitting the full q-dependence of inelastic scattering, we confirm that that the Johari-Goldstein ($\beta_{JG}$) relaxation in PC is indistinguishable from metabasin transitions.