High-coverage stable structures of potassium adsorbed on single-walled carbon nanotubes

We have investigated the structures of potassium adsorbate on single-walled carbon nanotubes and graphite using the first-principles approach. We show that the curvature of carbon nanotube surface enhances the stability of high coverage structures of adsorbate. We predict that two types of high coverage structures $\mathrm{}(x=1/2,2/3\mathrm{})\mathrm{}$ are stable for adsorption on the (6,0) carbon nanotube in addition to low coverage structures of adsorbate on graphite. The dependence of the stability on the size of carbon nanotubes is analyzed.