Targeted Assembly of Colloidal Co-Crystals from Radical Voronoi Particles and the Importance of Radius Ratio

The additional degrees of freedom afforded to colloidal crystals by the introduction of a second particle type diversify potential applications if co-crystallization is possible. Often, however, co-crystallization is hindered in the absence of complementary attractive interactions. This is especially so in binary mixtures of hard shapes, where entropy may be maximized through demixing rather than co-crystallization. Here we report an inverse design protocol for assemblies of CsCl-, NaCl-, and cubic ZnS-type binary colloidal crystals based on the radical Voronoi tessellation [1]. Previous works show that particles whose shapes match those obtained from a simple Voronoi tessellation of the target structure [2] rarely self-assemble that structure at kinetically accessible particle volume fractions [3]. Using hard particle Monte Carlo simulation, we show how judicious choice of particle size ratio and stoichiometry of the fluid phase [4] can result in reliable self-assembly of target co-crystals. We further show that, at the optimum size ratio, the radical Voronoi shapes and those designed using the digital alchemy method [5] are similar.

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[2] B.A. Schultz et al., "Symmetry Considerations for the Targeted Assembly of Entropically Stabilized Colloidal Crystals via Voronoi Particles", ACS Nano, 2015, 9(3), p. 2336-2344.

[3] R. K. Cersonsky et al., "Relevance of packing to colloidal self-assembly", Proceedings of the National Academy of Sciences, 2018, 115(7), p. 1439-1444.

[4] R.A. LaCour et al., "Tuning Stoichiometry to Promote Formation of Binary Colloidal Superlattices", Physical Review Letters, 2022, 128(18), p. 188001.

[5] G. van Anders et al., "Digital Alchemy for Materials Design: Colloids and Beyond", ACS Nano, 2015, 9(10), p. 9542-9553.