Date/Time
Date(s) - 09/09/2026
10:30 am - 11:30 am

BSB 108

Dr. Laura Filion
Associate Professor
Utrecht University

Title: Colloidal quasicrystals: How entropy can lead to forbidden symmetries

Abstract:

Quasicrystals are one of the most intriguing phases in classical matter and challenge our usual understanding of crystalline order. Unlike conventional crystals, they can exhibit rotational symmetries that are that are forbidden for periodic crystals, e.g. 10-, 12-, 18-, 20-fold symmetries — a feature that was central to their discovery by Dan Shechtman in 1984. While quasicrystals were first identified in atomic systems, they have since been observed in a growing variety of soft-matter systems, including nanoparticles, polymers, and micelles.
How simple can a system be and still exhibit such an unusual form of order? And what physical mechanisms drive the stabilization of a quasicrystal in the first place?
In this talk, we examine these questions as they relate to soft matter quasicrystals. In particular, we show how a system of simple hard spheres can be designed to form a quasicrystal, despite having no attractive interactions. Using a combination of event-driven molecular dynamics simulations and free-energy calculations, we demonstrate the crucial role of entropy in stabilizing this complex phase. We then turn to the question of how this order accommodates imperfections, and discuss the emergence and structure of point defects in quasicrystals. Together, these results illustrate how surprisingly rich structural behaviour can emerge from simple microscopic building blocks.