Electronic energy band structure of uniaxially deformed (5,5) armchair carbon nanotube

Semiempirical molecular orbital calculations of the (5,5) armchair carbon nanotube give the Kekule structure in its ground state with two essentially different bonds (the bond lengths difference is 0.003 nm). This is a result of the Peierls distortions leading to tripled (compared with undistorted case) translational period. When the armchair nanotube is elongated, two first order deformational structural phase transitions are predicted. The first one at the elongation of 5% leads to doubling of a translational period (instead of tripling at smaller elongations). The second one at the elongation of 13% leads to the quinoid type structure. The dependence of the electronic energy-band structure of the (5,5) carbon nanotube on elongation is investigated using the tight binding approximation. The transition from narrow-gap semiconductor to metal is predicted at the elongation of 5%, indicating that the uniaxially deformed armchair carbon nanotube at greater elongation (more than 5%) remains metallic at all temperatures.