Controlling morphology in hybrid isotropic/patchy particle assemblies

Abstract

Brownian Dynamics is used to study self-assembly in a hybrid system of istotropic particles (IPs), combined with anisotropic building blocks that represent special "designer particles". Those are modeled as spherical patchy particles (PPs) with binding only allowed between their patches and IPs. In this study, two types of PPs are considered: Octahedral PPs (Oh-PPs) and Square PPs (Sq-PPs), with octahedral and square arrangements of patches, respectively. The self-assembly is additionally facilitated by the simulated annealing procedure. The resultant structures are characterized by a combination of local correlations in cubatic ordering, and a symmetry-specific variation of bond orientation order parameters (SymBOPs). By varying the PP/IP size ratio, we detected a sharp crossover between two distinct morphologies, in both types of systems. High symmetry phases, NaCl crystal for Oh-PP and square lattice for Sq-PP, are observed for larger size ratios. For smaller ones, the dominant morphologies are significantly different, e.g., Oh-PPs form a compact amorphous structure with predominantly Face-to-Face orientation of neighboring PPs. Unusually for a morphology without a long range order, it is still possible to identify well organized coherent clusters of this structure, thanks to the adoption of our SymBOP-based characterization.

SAT-assembly: A new approach for designing self-assembling systems

“…The tuning can be achieved with different strategies such as minimizing the deviation from the target [5][6][7][8], statistical fluctuations [9,10], and more recently via learning algorithms [11,12]. Geometrical approaches, on the other hand, use geometric features of the target structure to constrain the symmetry of the building blocks [13][14][15][16][17][18][19][20][21][22][23]. While being more readily realizable in experiment, designing the interactions often requires a high degree of geometrical intuition.…”