Structural and Electronic Properties of Finite Carbon Chains Encapsulated into Carbon Nanotubes

Finite carbon chains encapsulated into carbon nanotubes are investigated by using first-principles calculations based on spin density functional theory. Dimerization is observed in carbon chains formed by an even number of carbon atoms, but not in carbon chains containing an odd number of carbon atoms. All carbon chains inside the carbon nanotubes are spin-polarized due to spin-split energy levels around the Fermi level. By comparing the results of carbon chains inside the carbon nanotubes and isolated charged carbon chains, we found that the charge transfer from the carbon nanotubes to the carbon chains leads to the structure transformation and the spin-polarization of the carbon chains when encapsulated inside the carbon nanotubes, whereas the orbital hybridization removes the degeneracy of energy levels around the Fermi levels. Our results provide a deep understanding on the interaction between the carbon chains and the carbon nanotubes.