On the metallicity of some carbon nanotubes

Abstract

Some zigzag and all armchair single-walled carbon nanotubes are believed to behave as metals. However, recent experimental results suggest that only armchair single-walled carbon nanotubes show typically metallic behavior. It has been suggested that metallic zigzag nanotubes are not true metals but small-gap semiconductors. Here we show, through simple quantum chemical calculations, that these zigzag nanotubes exhibit less metallic character than armchair ones because in the former, fewer electrons can flow freely between the valence and conduction bands. Therefore, they can be considered semimetals and not small-gap semiconductors.