Carbon can be found in nature in a huge variety of allotropic forms and recent research in materials science boosted the development of technological materials based on nanocarbon. Thought as a building-block with sp2 or sp3 hybridization, following a bottom-up approach, we will show how graphene and diamond molecules built up, and how their properties vary with size, up to the upper limit of bulk graphite and diamond. On the other hand, sp2 carbon gives rise to an impressive number of different materials such as carbon nanotubes, graphene nanoribbons, porous carbon, and fullerene. As for any crystalline phase, the crystal structures of natural carbon allotropes (i.e., graphite and diamond) contain various types of imperfections. These so-called lattice defects are classified by their dimension into 0- (point), 1- (line), 2- (planar), and 3-dimensional (volume) defects. Lattice defects usually control the physical properties of minerals and are commonly a fingerprint of the geological environment in which the minerals form and modify. A direct observation of lattice defects is commonly accomplished by transmission electron microscopy. This lecture will present and discuss the ideal and real structures of carbon allotropes, the energetics of lattice defects, and their significance in understanding geological processes and conditions.
Scientific editing by Igor Maria Villa