Flat Surfaces Induce Crystallization of Stubborn Nanoparticle Shapes

With the synthesis of uniformly shaped nanoparticles, a huge range of nanoparticle superlattices have been self-assembled. Hard particle simulations have proven to be useful tools for predicting nanoparticle superlattice structures. Though most symmetric or regular shapes crystallize in simulation many similar shapes never do. These stubborn shapes instead fail to form long-range ordered structures. In this work, we show that most previously reported non-crystallizing shapes will crystallize by adding a flat, hard wall to self-assembly simulations. We survey the entire hard particle self-assembly literature and find of 105 stubborn shapes studied, 73% now crystallize with a wall. Using hard particle meta dynamics simulations [1], we show the wall lowers the energy barrier to crystallization, allowing these shapes to crystallize with a wall.  We further show that the formerly stubborn shapes form crystals with local motifs identical to those present in similarly shaped easily crystallizing particles. Our results indicate that many more shapes than previously reported can crystallize in simulation and, presumably, experiment by employing surfaces. 

[1] C. S. Zhao, S.-T. Tsai, and S. C. Glotzer, “Hybrid Monte Carlo Metadynamics (hybridMC-MetaD),” (2025) doi: 10.48550/arXiv.2508.15942.