The interaction energy E
(in meV) as a function of the fullerene C
displacement z along the nanotube axis and the angle φ of the fullerene rotation about the nanotube axis. (a) The (8,8) carbon nanotube with the Kekule structure; (b) the (8,8) carbon nanotube with the structure of metallic phase. The energy is given relative to the energy minima. The equipotential lines are drawn at an interval 0.2 meV.