A detailed analysis was made of topological and geometrical defect clusters in hexagonal networks. The conditions which had to be met by a cluster, for it to be embedded in an hexagonal network, were listed. These were related to the sequence of saturated (3-connected) and unsaturated (2-connected) vertices at the periphery of the cluster (vertex sequence). The type of hexagonal network (perfect, dislocated, disclinated) in which a defect was embedded depended upon simple parameters which could be deduced from the vertex sequence. Equivalent clusters could be embedded in hexagonal networks of the same topology, and equivalence classes were identified for all types of cluster. Disclination defects with a given strength could fall into one or more classes, depending upon that strength. In the case of dislocation defects (with zero strength) there were infinitely many classes; each defined by a vector. The strain field and strain-energy density in the hexagonal network around a single defect cluster was evaluated for geometrical and topological defects of any type by using a continuum approach.

Defect Clusters in Hexagonal Networks: Characterization and Strain Field. M.A.Fortes, M.F.Vaz: Journal of Physics - Condensed Matter, 1998, 10[34], 7519-34