Shells of atoms

It is interesting to consider how a solid evolves during the earliest stages of growth. The atoms reorganize into a completely new structure each time an atom is added when a cluster is very small. However, this cannot go on indefinitely. Eventually, a preferred symmetry becomes frozen into the cluster. Further growth takes place by adding layers of atoms to this frozen core. One layer is sometimes referred to as a geometric shell of atoms. Shell structure is the subject of this article.