Crystallographic symmetry effect on the nucleation in non-equilibrium aggregation pattern

Some non-equilibrium patterns formed in different systems are composed by crystallites with correlations in their crystallographic orientation. This reflects the fact that crystallographic symmetry controls the successive nucleation in the crystallite aggregating process. Based on the crystallographic symmetry, a new classification to describe the different kinds of anisotropy for non-equilibrium aggregation pattern has been proposed: parallel aggregation, twin aggregation and radial (random) aggregation. This new classification can clarify the different anisotropy related to the crystal point group, which the previous classifications cannot. The nucleation mechanisms for these three kinds of patterns are also discussed based on the symmetric relationship among the crystallites. It is shown that the crystallographic symmetry plays an important role not only on the crystal polyhedral shape formed by growth, but also on the aggregation pattern formed by nucleation.