Ionic Cohesion and Electron Doping of Thin Carbon Tubules with Alkali Atoms

Cohesion properties between carbon nanotubules and potassium atoms are studied using a first-principles total-energy and band-structure approach. The present calculations which assume linearly aligned arrangements of K atoms inside and outside of tubules suggest that the classical wetting picture of capillary action is not applicable on a microscopic scale. Charge transfer occurs from the K atoms to the tubule resulting in ionic cohesion. The energy barrier for sliding motion of the K atoms is found to be comparable to that of K diffusion in graphite intercalated compounds. The possibility of superconductivity of doped tubules is also discussed.