A simple mechanism for emergent chirality in achiral hard particle assembly

Abstract

For centuries, chirality has been appreciated as a key component in understanding how matter orders. While intuitively chiral particles can self-assemble into chiral superstructures, it is often less obvious how achiral particles can do the same. Here we show that there is a potentially general, packing-based mechanism that explains why many simple, two-dimensional achiral particles assemble into chiral materials. Namely, we use simulations of hard, regular polygons to show that the subtle shape modification of corner rounding surprisingly can induce chiral symmetry breaking by deforming the underlying close-packed lattice. The mechanism quantitatively explains recent experimental results reporting chiral symmetry breaking in the hard triangle system. Moreover, it predicts similar symmetry breaking in the rounded hard rectangle system, which we verify through simulations. Because effective corner rounding is easily realized by modulating repulsive interactions in real systems, this simple mechanism suggests tremendous potential for creating dynamically tunable chiral surfaces with a variety of applications.

Phase behaviour and gravity-directed self assembly of hard convex spherical caps

“…A variety of shapes in bulk and under the influence of external fields have been explored including spherocylinders [15][16][17][18] , cut-spheres 23 [24][25][26][27][28] , dimers [29][30][31] , bowl-like particles [32][33][34] , concave spherical caps [35][36][37] , polyhedra [38][39][40][41][42] , and a variety of branched particles [43][44][45][46] , just to mention few examples. An assumption behind these studies is that the effect of gravitational forces is negligible, corresponding to a situation of colloidal particles embedded within a density matched (implicit) medium.…”

Heterogeneous Interactions Promote Crystallization and Spontaneous Resolution of Chiral Molecules

“…In our efforts, we build on previous computa- tional work that has demonstrated the usefulness of simple molecular models in elucidating structure formation mechanisms of chiral molecules. 16,20,21,[42][43][44][45] Our study is based on a family of coarse-grained models of chiral molecules. The computational efficiency of these models allows us to simulate the crystallization dynamics of a wide range of molecular shapes and interactions, and to fully determine the thermodynamic landscape of crystal structures.…”

Depletion-driven crystallization of cubic colloids sedimented on a surface

“…12–14 Recently, cubic colloids have been synthesized experimentally, 15–19 and accordingly, simulations have been performed on freely rotating cubes, squares or truncated polyhedra, 20–28 and on a family of shapes which smoothly varies between cubes and spheres 29–32 or squares and circles. 33–35 In addition, hard cubes under shear have also been studied with experiments and simulation. 36 …”