Structural properties of Haeckelite nanotubes

Abstract

The name 'Haeckelite' has been proposed to designate a three-fold coordinated network generated by a periodic arrangement of pentagons, hexagons and heptagons (Terrones H et al 2000 Phys. Rev. Lett 84 1716). Starting from a planar Haeckelite array, tubular structures are obtained by applying the same wrapping procedure as for the usual nanotubes, which are rolled up sheets of graphene. This paper is a short review of the structural properties of Haeckelite nanotubes, as investigated by computer molecular modelling. The Haeckelite nanotubes may adopt various shapes, among which coiled structures, double-screw molecules, corrugated cylinders, and pearl-necklace-like nanotubes are the most spectacular. It is shown that some of these structures may explain exotic forms of C nanostructures revealed by electron microscopy on samples produced experimentally. The identification of the possible Haeckelite structure of a nanotube by electron diffraction and scanning tunnelling microscopy is discussed.