Electronic structure of carbon nanotubes

A study of the electronic structure of carbon nanoparticles has been carried out using the methods of quantum chemistry and X-ray emission spectroscopy. Fragments of (n, 0) tubes with n = 6,...,11 and of (5,5) -(10,0) tubes were calculated using PM3 method. The dependence of the electronic structure of the fragment on length and symmetry was investigated. The structure of the frontier orbitals was shown to change regularly depending on the tube chirality. Band structure of (n, 0) and (5,5) tubes was studied by the tight-binding method. A comparison of the basic blocks of the molecular orbitals (MOs) of the fragment and bands of (6,0) and (5,5) tubes was carried out. Experimental CK alpha spectra for single-wall and multiwall carbon nanotubules were obtained. These spectra agree satisfactorily with the theoretical spectra plotted as the results of cluster calculations. The structure of the valence zone for the central hexagons of the nanotube fragments keeps the basic features in the series of tubes of various chirality. At the same time a considerable change of the electronic state of the boundary carbon atoms is observed.