Point defect

A localized crystal defect such as a vacancy, substitutional impurity or interstitial atom.

A missing carbon-atom inventory in graphene. Local reconstruction changes the nearby ring pattern and electronic states; irradiation and subsequent annealing can change the reconstruction.

A graphene vacancy defect with two carbon atoms removed. A common adjacent-pair reconstruction has a 5–8–5 ring arrangement; other reconstructed arrangements exist and can be selected by energetic processing.

A graphene vacancy defect with one carbon removed. A common reconstruction has a pentagon and nine-membered ring with residual under-coordination. The reconstructed geometry need not retain the symmetry of the unrelaxed missing-atom site.

An extra atom of the host material accommodated outside the ordinary lattice-site inventory. It can migrate, recombine with a vacancy, or join a cluster.

An unoccupied site in an otherwise specified crystal structure. Equilibrium vacancies and an irradiation-driven vacancy supersaturation have different origins.

A vacancy population above its thermal-equilibrium value at the specified temperature. It can drive net vacancy absorption by growing cavities when competing sinks and emission permit.

A vacancy and a displaced atom occupying an interstitial position. Recombination restores the occupied lattice site; spatial separation or trapping can allow the defects to survive.