Ordering and Melting in Colloidal Molecular Crystal Mixtures

We show in simulations that a rich variety of novel orderings such as pinwheel and star states can be realized for colloidal molecular crystal mixtures at rational ratios of the number of colloids to the number of minima from an underlying periodic substrate. These states can have multi-step melting transitions and also show coexistence in which one species disorders while the other species remains orientationally disordered. For other mixtures, only partially ordered or frustrated states form.