First-principles study of transition-metal-doped single-walled carbon nanotubes

We study the effect of doping transition metals (TMs) into single-wall carbon nanotubes by using first-principles calculations. For metallic isolated (3,3) single-wall carbon nanotubes, doping of Mn, Fe and Co makes them semi-metallic, while Ni doping leads to semiconductors. For (3,3) nanotube bundles, a Co atom in the unit cell makes it exhibit semiconductor character. With two or three Co and Ni atoms doped into the bundle, the impurity atoms change the nanotube to semi-metal. In particular, the Mn2C12 and Mn3C12 bundle have comparable large magnetic moments, suggesting that such TM-doped nanotubes could be useful as nanomagnets.