ENERGY-BAND STRUCTURE FEATURES OF SOME CRIMPED-SHAPE NANOTUBES

Energy spectra of four stereoregular carbon quasi-1D-macromolecules wi th polyhedral elementary units containing 60 or 58 atoms were calculat ed by the crystalline orbital method in the valence approach. The EHT (see R.Hoffmann, J.Chem.Phys. 1963, 39, 1397) with standardized weight ed non-diagonal elements of the matrix Hamiltonian was used. Atomic co ordinates of the elementary units of carbon systems under consideraton were determined as a result of energy optimization of conforming trim ers by the MNDO/PM3 methods. Geometries of inner monomers were used fo r modeling macromolecule structures. It was found that the widths of e nergy gaps of three systems [C-60](n) under consideration are located in the interval from 1.3 to 1.5 eV. Besides, quasi-localized energy le vels were found in the spectrum gaps of these carbon quasi-1D-systems. The energy gap of the fourth structure with the elementary unit consi sting of 58 atoms is relatively small approximate to 0.3 eV. Conclusio n about necessity of the (sigma-->pi) interaction accounting while mod eling energy spectra of crimped-shape nanotubes was made.