Irregular network of extended defects in graphene and a new criterion of the crystal lattice melting

Investigation of graphite defects has long and rich history. However, it turned out, that most point defects in graphene, such as vacancies or topological Stone-Wales defect, have high formation energies, preventing them from formation in large quantities. Recently, we have proposed a new type of extended defects in graphene, with formation energy per atom only slightly above the melting temperature. This means, that these planar defects may occur near the melting temperature in sufficient quantities to influence the thermodynamic properties of graphene. Still, there is discrepancy between thermodynamic properties of these defects and their topology, which can be successfully resolved by proposition of a new defects' type – irregular network of extended defects, which will be described in this paper. The study of network stability from these defects enables us to formulate a new criterion of crystal lattice melting, which supersedes the Lindemann/Born criteria. [Display omitted] •We propose existence of irregular defect network in graphene.•A new crystal melting criterion is put forward.•This supercedes existing Born/Lindemann criteria.