 Stone–Wales defect

A bond rotation that changes four hexagons in a graphitic carbon network into a pentagon-heptagon-heptagon-pentagon ring arrangement without adding or removing atoms.

The Stone-Wales defect is a type of defect that can occur in graphene and other two-dimensional materials. It involves a local rearrangement of carbon atoms in the hexagonal lattice structure of graphene. The defect is characterized by the rotation of a pair of carbon-carbon bonds, which transforms one hexagonal ring in the lattice into a series of two adjacent pentagonal and heptagonal rings.