Phase behavior and structure of colloidal bowl-shaped particles: simulations

TL;DR

This study uses computer simulations to explore the phase behavior and structural transitions of bowl-shaped colloidal particles, revealing stable phases, novel crystal structures, and the effects of particle shape on phase stability.

Contribution

It provides new insights into the phase diagram of bowl-shaped particles, including the stability of various phases and the spontaneous formation of columnar structures.

Findings

Worm-like fluid phase forms at low density.

Columnar phase emerges spontaneously for deep bowls.

Four novel crystal phases identified.

Abstract

We study the phase behavior of bowl-shaped particles using computer simulations. These particles were found experimentally to form a meta-stable worm-like fluid phase in which the bowl-shaped particles have a strong tendency to stack on top of each other [M.Marechal et al, Nano Letters 10, 1907 (2010)]. In this work, we show that the transition from the low-density fluid to the worm-like phase has an interesting effect on the equation of state. The simulation results also show that the worm-like fluid phase transforms spontaneously into a columnar phase for bowls that are sufficiently deep. Furthermore, we describe the phase behavior as obtained from free energy calculations employing Monte Carlo simulations. The columnar phase is stable for bowl shapes ranging from infinitely thin bowls to surprisingly shallow bowls. Aside from a large region of stability for the columnar phase, the phase diagram features four novel crystal phases and a region where the stable fluid contains worm-like stacks.