Phase behaviour of a system of inverse patchy colloids : a simulation study

Abstract

In this thesis, we consider mesoscopic colloidal particles with a negatively charged equatorial region and two positively charged polar caps. We refer to them as "inverse patchy colloids", by which we imply that charge-like regions repel each other, while oppositely charged regions attract each other. We model the system via a recently introduced coarse-grained description and we investigate the effect of the interplay between the directional attractive and repulsive interactions on the equilibrium phase diagram; this includes the disordered fluid phase, two spatially and orientationally ordered lattices as well as a plastic crystal, where the orientation of the particles is almost randomly distributed. Via a combination of evolutionary algorithms (that predict ordered candidate structures at vanishing temperature) and free energy calculation techniques (involving Monte Carlo simulations), we are able to identify the regions of thermodynamic stability of the fluid phase and the three solid structures.