Energetics and electronic structure of a polyacetylene chain contained in a carbon nanotube

Using density-functional theory, we calculate the energy and electronic structure of a polyacetylene chain interacting with various carbon nanotubes. We find that polyacetylene chains are weakly attracted exohedrally or endohedrally to nanotubes. The equilibrium separation between the chain and the wall is close to 3.3 Å, suggesting an energetic preference for polyacetylene to be enclosed in nanotubes wider than the ~5,5! tube. The chains are expected to be spontaneously pulled into open nanotubes by forces amounting to a fraction of a nanonewton. Electronic structure calculations reveal the occurrence of a peak at the Fermi level in the electronic density of states, caused by the weak interaction between polyacetylene and the carbon nanotube, which may facilitate the onset of superconductivity in this system.