8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Wed 711:10-14:00P5.39Predicting crystal structures and phase behavior forfaceted non-convex colloids and nanoparticlesJoost de Graaf, 1 René van Roij, 1 and Marjolein Dijkstra 11 Utrecht University, Princetonplein 1, 3584 CC, Utrecht, NetherlandsWe present a novel numerical technique to rigorously investigate dense regular structures ofirregular, non-convex and even punctured objects. With this method we reduce the complexproblem of studying such systems by simulations in a two-fold manner. Crystal structures areanalyzed on the level of the unit cell [1] and the particles within are broken down into triangularbase constituents [2], for which the hard particle overlap can be easily determined. As an example,we analyze the behavior of recently synthesized octapod-shaped nanocrystals [3] in solution. Acombination of simulations and theory allow us to explain the mechanism behind experimentallyobserved aggregation of these octapods into interlocking chains and 3D superstructures. Theself-assembly process is found to be driven by Van-der-Waals forces and proceeds via hierarchicalorganization. In addition, we study the applicability of simulations of bowl-shaped particles [4] todescribe a system of colloidal caps [5]. Results for this simple model agree with those obtainedusing our method for a more realistic approximation [5]. The essential shape-related physics ofthe colloidal caps is thus shown to be captured by the bowl shape. Using our method, we canspecifically target an emerging field in nanoparticle and colloid research, which focuses on theself-assembly of non-convex particles. We anticipate our investigation to be the starting pointof an exploration of the self-assembled structures formed by such particles, which will rival thecurrent research effort on more conventional shapes.[1] L. Filion et al., Phys. Rev. Lett. 103, 188302 (2009).[2] J. de Graaf, M. Dijkstra, R. van Roij, Phys. Rev. E 80, 051405 (2009).[3] S. Deka et al., Nano Lett. 10, 3770 (2010).[4] M. Marechal et al., Nano Lett. 10, 1907 (2010).[5] C. Quilliet et al., Eur. Phys. J. E 27, 13 (2008).39