We present results from density-functional theory calculations on the geometrical and electronic structure of potassium-intercalated (4,4) armchair and (7,0) zigzag single-walled carbon nanotubes. Intercalation of potassium results in notable changes in the geometrical structure, in particular in the zigzag system in which the carbon–carbon bond lengths in the unit cell vary between 1.40 Å and 1.45 Å. The most prominent effect of K intercalation on the electronic band structure is a shift of the Fermi energy which occurs as a result of charge transfer from potassium to the carbon nanotube. In the case of the potassium-intercalated (7,0) nanotube the band structure and the position of the Fermi energy indicate a very good metallic conductor. The (4,4) nanotube has the potential to become superconducting due to the very high density of states at the Fermi energy which is obtained at high intercalation densities.

• Received 3 August 2004

DOI:https://doi.org/10.1103/PhysRevB.72.125420