Energy wave propogation in pristine and bi-crystal graphene

This study investigates the distribution and propagation of potential energy in graphene under tearing loads. Before crack extension, high potential energy accumulates at the crack tip. The distributions of the high potential energy are symmetrical and asymmetrical in pristine graphene and bi-crystal graphene with misorientation angle of 21.79∘, respectively. When a C–C bond breaks during the fracture of graphene, numerous energy waves successively arise from the crack tip, i.e., the two atoms linked by the broken bond. These atoms lose one bond constraint and turn into unstable states, and they displace with high accelerations. In pristine graphene, the energy waves present as hexagonal geometries, while the waveforms near the loading areas are compressed to flatter geometries. In bi-crystal graphene, the refractions of potential energy waves are observed when the energy waves propagate to the grain boundary (GB) and interact with it, and the waveforms are changed after the wave crosses the GB. For both pristine graphene and bi-crystal graphene, wrinkles are generated when the crack tip extends to the site sufficiently close to the vertical free boundary, and the wrinkles are always nearly parallel to the horizontal free boundary and move along with the motion of the crack tip.