Electrical and mechanical properties of distorted carbon nanotubes

We have calculated the effects of structural distortions of armchair carbon nanotubes on their electronic and electrical properties. We found that the bending of the nanotubes decreases their transmission function in certain energy ranges and leads to an increased electrical resistance. Electronic s tructure calculations show that these energy ranges contain localized state s with significant sigma-pi hybridization resulting from the increased curv ature produced by bending. Twisting strongly affects the electronic structu re of nanotubes (MTs). Normally metallic armchair (n,n) NT's develop a band gap which initially scales linearly with twisting angle and then reaches a constant value. This saturation is associated with a structural transition to a flattened helical structure. The computed values of the twisting ener gy and of the band gap are strongly affected by allowing structural relaxat ion in the twisted structures, Finally, our calculations show that the larg e contact resistances observed for single-wall NT's are likely due to the w eak coupling of the NT to the metal in side bonded NT-metal configurations. [S0163-1829(99)02943-4].