Zone-center instability of C(5,0) carbon nanotubes inside AlP O4 -5 channels

The electronic structure of C(5,0) carbon nanotubes inside zeolite channels is analyzed. We confirm the occurrence of the metal-semiconductor transition which has been previously predicted in the case of isolated tubes. The interaction with the zeolite matrix does not prevent the spontaneous metal-semiconductor instability at room temperature, even though it reduces the magnitude of the band gap in the distorted stable phase. An empirical potential modeling, which allows the study of the tube and zeolite relaxation without the constraint of periodic boundary conditions, does not lead to the conclusion that some tubes could remain metallic.