Characterizing Multi-Flavored Assembly of Two Dimensional Binary Colloidal Crystals

DNA-functionalized colloids are routinely used to assemble complex nanoscale crystalline lattices; for sufficiently high grafting density, the pairwise interactions between these colloids can be robustly controlled by tuning the length of the grafts and base pairs composition on the colloids. In a multicomponent mixture, the latter can be employed to decouple the cross interactions between unlike particles from the interactions between like particles. Here we investigate the consequences of tuning the cross-interaction between unlike species in a binary mixture on the types of self-assembled structures which form. We use a combination of Monte Carlo, molecular dynamics, and free energy methods to examine the relative stability of an array of possible structures, which range from low symmetry structures such as strings, to various crystal lattices with either 4- or 6-fold symmetry typically. The regimes of stability for different lattices can be described in terms of a balance of cohesive and adhesive interaction across a range of particle size asymmetries. In the zero-temperature limit, we identify parameter space which provides a semi-universal description of the regimes in which different symmetries are found. We then map out how these regimes change as a function of temperature starting from the zero-temperature (ground state) limit up to the melting point.