Calculating the symmetry number of flexible sphere clusters

Abstract

We present a theoretical and computational framework to compute the symmetry number of a flexible sphere cluster in ${\mathbb{R}}^3$, using a definition of symmetry that arises naturally when calculating the equilibrium probability of a cluster of spheres in the sticky-sphere limit. We define the sticky symmetry group of the cluster as the set of permutations and inversions of the spheres which preserve adjacency and can be realized by continuous deformations of the cluster that do not change the set of contacts or cause particles to overlap. The symmetry number is the size of the sticky symmetry group. We introduce a numerical algorithm to compute the sticky symmetry group and symmetry number, and show it works well on several test cases. Furthermore we show that once the sticky symmetry group has been calculated for indistinguishable spheres, the symmetry group for partially distinguishable spheres (those with non-identical interactions) can be efficiently obtained without repeating the laborious parts of the computations. We use our algorithm to calculate the partition functions of every possible connected cluster of 6 identical sticky spheres, generating data that may be used to design interactions between spheres so they self-assemble into a desired structure.

arXiv commentNew version, 30 pages, 9 figures

References in corpus (10)

• Euclidean Distance Matrices: Essential Theory, Algorithms and Applications
• Why Colloidal Systems can be described by Statistical Mechanics: Some not very original comments on the Gibbs paradox
• A geometrical approach to computing free energy landscapes from short-ranged potentials
• Two-Dimensional Clusters of Colloidal Spheres: Ground States, Excited States, and Structural Rearrangements
• Enumerating rigid sphere packings
• Computational topology for configuration spaces of hard disks
• Testing the Foundations of Classical Entropy: Colloid Experiments
• Sticky-sphere clusters
• Structural analysis of high-dimensional basins of attraction
• Free energy of singular sticky-sphere clusters