Theoretical study of alkali-atom insertion into small-radius carbon nanotubes to form single-atom chains

Using first-principles total energy calculations, we found that the doping of Li into (6,0) nanotubes has no insertion barrier if the tube mouth is passivated. The diffusion barrier is extremely small inside the nanotube, and Li atoms prefer to reside along the tube axis. The reaction is strongly exothermic. The Li-Li interaction inside the nanotube is repulsive but strongly screened. These results point to the possibility of realizing a truly one-dimensional atomic wire inside certain small-radius nanotubes that are fabricated inside zeolite channels if Li is used as dopant, but other elements like K would not serve the purpose.