What do we learn from the local geometry of glass-forming liquids?

TL;DR

This study investigates the local geometric structure of glass-forming liquids using Voronoi analysis, revealing universal properties and linking free volume to relaxation dynamics.

Contribution

It demonstrates the universality of Voronoi volume and asphericity distributions and connects free volume behavior to the glass transition temperature.

Findings

Voronoi volume and asphericity distributions are universal in dense liquids.

Average free volume extrapolates to zero at the glass transition temperature.

Free volume correlates with the Debye-Waller factor.

Abstract

We examine the local geometry of a simulated glass-forming polymer melt. Using the Voronoi construction, we find that the distributions of Voronoi volume $P(v_V)$ and asphericity $P(a)$ appear to be universal properties of dense liquids, supporting the use of packing approaches to understand liquid properties. We also calculate the average free volume $<v_f>$ along a path of constant density and find that $<v_f>$ extrapolates to zero at the same temperature $T_0$ that the extrapolated relaxation time diverges. We relate $<v_f>$ to the Debye-Waller factor.