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The electronic band structure and density of states of (8,8) armchair and (14,0)
zigzag single walled carbon nanotubes (SWCNT) are investigated using densityfunctional
calculations. The band structure of the pure (14,0) zigzag nanotube indicates that it is a
semiconductor where as the band structure of pure (8,8) armchair tube exhibits metallic
behavior. When a titanium chain is adsorbed on the carbon nanotube, the (14,0) zigzag tube
changes from semiconductor to metal and the (8,8) armchair tube transforms from metal to
semiconductor. In both the cases there is a net transfer of charge from the metal chain atom to
the carbon atom. The delocalized 3d electrons from the titanium chain generate additional
states in the band gap regions of the semiconducting tubes transforming them into metals. The
band structures of Ti adsorbed nanotubes are completely different from that of pure
nanotubes. The band structure results are used to study the superconducting behaviour of pure
(8,8) armchair nanotube and the Ti adsorbed (14,0) zigzag nanotube. The superconducting
transition temperatures, Tc, for the pure (8,8) nanotube and the Ti adsorbed (14,0) nanotube
are computed for different values of Debye temperature. The electron-phonon interaction and
superconducting transition temperature are small in (8,8) armchair tube and considerable in Ti
adsorbed (14,0) zigzag tube. Based on this, we hint at room temperature superconductivity in
carbon nanotube.
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