Healing of a topological scar: Coordination defects in a honeycomb lattice

A crystal structure with a point defect typically returns to its ideal local structure within a few bond lengths of the defect; topological defects such as dislocations or disclinations also heal rapidly in this regard. Here we describe a simple point defect – a two-fold atom incorporated at the growth edge of a honeycomb lattice – whose healing may require a defect complex spanning many atoms. Topologically, the two-fold atom disappears into a single “long bond” between its neighbors, thereby making a pentagonal disclination. But chemically, this disclination occupies as much physical space as a six-fold ring. This incompatibility of chemistry and topology can cause a damped oscillation of the Gaussian curvature that creates an expansive healing region, a topological scar.