Crystal phases of two dimensional assembly of triblock Janus particles

Recent experimental work on spherical colloidal particles decorated with two hydrophobic poles separated by an electrically-charged middle band (triblock Janus particles) has documented self-assembly into a Kagome two-dimensional lattice, when particles are confined by gravity at the bottom of the sample holder [Q. Chen {\em et. al.}, Nature, in press]. Here we assess the ability of a previously proposed simple two-patch effective potential to reproduce the experimental findings. We show that the effective potential is able to reproduce the observed crystallization pathway in the Kagome structure. Based on free energy calculations, we also show that the Kagome lattice is stable at low temperatures and low pressure, but that it transforms into a hexagonal lattice with alternating attractive and repulsive bands on increasing pressure.