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

BN Katz and V Crespi, CARBON, 238, 120193 (2025).

DOI: 10.1016/j.carbon.2025.120193

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.

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