Phase transitions and self-organization of Janus disks in two dimensions studied by Monte Carlo simulations.

The phase behavior of Janus disks on a square lattice is studied using the Monte Carlo method. A particle is composed of two different parts, A and B. The interactions between neighboring particles depend on their orientations. To control the strength of the interactions, we use energy parameters characterizing AA,BB, and AB contacts. The phase diagrams are estimated. We found two phase transitions, namely first-order transitions between colloidal-rich and colloidal-poor phases, and continuous order-disorder transitions to different ordered phases. A variety of ordered structures occurs depending on the relation between the energy parameters and on the fluid density. The influence of energy parameters on the phase diagram topology and critical parameters is shown. The competition between phase transitions and self-organization is discussed.