Electronic and structural properties of multiwall carbon nanotubes

We calculate the potential energy surface, the low-frequency vibrational modes, and the electronic structure of a (5,5)@(10,10) double-wall carbon nanotube. We find that the weak interwall interaction and changing symmetry cause four pseudogaps to open and close periodically near the Fermi level during the soft librational motion at $\nu \lesssim 30{\mathrm{cm}}^{\mathrm{-}1}.$ This electron-libration coupling, absent in solids composed of fullerenes and single-wall nanotubes, may yield superconductivity in multiwall nanotubes.