Analysis of non-planar graphitic structures: from arched edge planes of graphite crystals to nanotubes

A unified approach to the analysis of the mechanisms that lead to the edge reconstruction of graphite and growth of a variety of non-planar graphitic structures, such as nanotubes, is suggested. Transmission electron microscopy (TEM) shows that nano-arches are formed on the edge planes of natural and synthetic graphite, as well as graphite polyhedral crystals, which are built of graphene sheets; this makes the edge reconstruction of graphite different from the surface reconstruction of other crystals. A theoretical study of edge zipping in graphite and formation of tubular carbon structures has been performed using an integrated approach combining molecular dynamics simulation and analytical continual energetics modeling. The suggested theoretical framework describes the formation of curved surfaces in a wide range of dimensions, which is a general feature of the growth of layered materials. Layered materials isostructural to graphite, such as hexagonal BN, demonstrate similar edge structures and also form nanotubes. Thus, the ability of materials to form arches as a result of edge reconstruction points out to their ability to form nanotubes and vice versa. TEM studies of graphite and hexagonal boron nitride provide experimental verification of our analytical model.