Density functional calculations are carried out for the La-2@C-80 derivatives to investigate whether the motion of metals encapsulated inside fullerenes is controlled by exohedral addition. It is shown that the three-dimensional random motion of two La atoms in La-2@C-80 can be restricted to the circular motion in a plane by attaching electron-donating molecules on the outer surface of the C-80 cage. It is expected that the two-dimensional circular motion will help to induce a unique electronic or magnetic field. (C) 2003 Elsevier Science B.V. All rights reserved.