Figure 11
(a) Graphene is a 2D structure made of a honeycomb lattice of carbon atoms (in black on the picture). The standard primitive hexagonal lattice is generated by the pair in complex notations defining the unit cell drawn in gray. The point symmetry group is 6m which can be generated by the two mirrors M and . (b) Generating coincidence lattices by rotation is easily obtained by applying rotations α around the origin that superpose nodes deduced from each other by the mirror along the real axis transforming the node into
n+jm. Because of the hexagonal symmetry, choosing point with
n,m coprime in the region between the mirrors M and is sufficient for generating all the possible rotations of coincidence angles α and . |