Entropy-driven self-assembly of novel phases

Entropy driven phase transitions have been of interest for more than half a century. Although early work on hard-sphere freezing was originally met with skepticism, phase transitions in hard particles are now generally accepted. While the behaviour of hard spheres and rods has remained an active focus of research for decades, entropy-driven phase transitions of more complicated hard particles have recently attracted great interest. This new interest has arisen, at least partially, due to advances in (nano) particle synthesis: hard particles are not simply toy theoretical problems, many are now experimentally realizable systems.

In this talk I will discuss the phase diagrams of two entropy-driven systems which display unexpected phase behaviour: a binary mixture of hard spheres, and single component system consisting of hard cubes. In the case of the binary hard spheres, I show, for a size ratio around 0.3, that there is a stable, completely tunable interstitial solid solution. In the case of the cubes, we find a stable crystal with 6% vacancies: orders of magnitude larger than is typical in simple, single component systems.