Molecular random tilings as glasses

TL;DR

This paper investigates how molecular random tilings, specifically of p-terphenyl derivatives on graphite, exhibit glass-like dynamic arrest through defect propagation, revealing insights into structural relaxation and dynamic heterogeneity.

Contribution

It introduces the analogy between random tilings and structural glasses, analyzing defect dynamics and their scaling properties to understand glassy behavior.

Findings

Tiling defects propagate and react, causing structural relaxation.

The dynamics exhibit scaling properties similar to glassy systems.

Connections are drawn between tiling defect dynamics and kinetically constrained models.

Abstract

We have recently shown [Blunt et al., Science 322, 1077 (2008)] that p-terphenyl-3,5,3',5'-tetracarboxylic acid adsorbed on graphite self-assembles into a two-dimensional rhombus random tiling. This tiling is close to ideal, displaying long range correlations punctuated by sparse localised tiling defects. In this paper we explore the analogy between dynamic arrest in this type of random tilings and that of structural glasses. We show that the structural relaxation of these systems is via the propagation--reaction of tiling defects, giving rise to dynamic heterogeneity. We study the scaling properties of the dynamics, and discuss connections with kinetically constrained models of glasses.