Observation of fivefold symmetry structures in computer models of dense packing of hard spheres

Structures of fivefold symmetry were obtained in computer models of dense packings of hard spheres containing crystalline regions (η > 0.639). Such structures are known to exist in small particles and thin films; however our models are specimens of a rather bulk phase (10 000 spheres in a box with periodic boundary conditions). This observation indicates that the fivefold structures can also exist in real bulk systems and play a role in the process of homogeneous crystallization of simple liquids and ageing of amorphous solids. The Voronoi–Delaunay approach is used for disclosing these structures. The Delaunay simplexes are the basic geometrical elements for this analysis. Having a quantitative measure for the shape of the simplexes, one can mark (color) Voronoi sites according to a given physical criterion to reveal aggregates of atoms with a given structure. Aggregates consisting of good tetrahedral simplexes are studied in this work.