Figure 1
Illustration: Alan Stonebraker

Figure 1: A series of Wigner crystal structures showing the arrangement of electrons in a circular island from an occupation number of N=3 to N=100. The electrons form ring structures as more electrons are added. At N=15 an inner ring of five electrons is formed, but at N=16 the additional electron is forced to the center to start a new ring. For large N, a triangular Wigner lattice forms in the center, while the outer electrons remain in rings.