  We investigated the adsorption of a single atom, hydrogen and aluminum, on
single wall carbon nanotubes from first-principles. The adsorption is
exothermic, and the associated binding energy varies inversely as the radius of
the zigzag tube. We found that the adsorption of a single atom and related
properties can be modified continuously and reversibly by the external radial
deformation. The binding energy on the high curvature site of the deformed tube
increases with increasing radial deformation. The effects of curvature and
radial deformation depend on the chirality of the tube.
