The atomic and electronic structure of narrow zigzag nanoribbons with finite length, consisting of graphene terminated by fluorine on one side, hexagonal (
h)
h-BN, and
h-SiC were studied with density functional theory. It is found that the asymmetry of nanoribbon edges causes a uniform curvature of the ribbons due to structural stress in the aromatic ring plane. Narrow graphene nanoribbons terminated with fluorine on one side demonstrate a considerable out-of-plane bend, suggesting that the nanoribbon is a fraction of a conical surface. It is shown that the intrinsic curvature of the narrow nanoribbons destroys the periodicity and results in a systematic cancellation of the dipole moment. The in- and out-of-plane curvature of thin arcs allows their closure in nanorings or cone fragments of giant diameter. Using the fragment molecular orbital method, we optimized the structure of a planar giant arc and a closed ring of
h-BN with a diameter of 105 nm.
Keywords:
zigzag nanoribbons; hexagonal atomic lattices; fluorine-terminated graphene