Mercator maps of orientations of a C60 molecule in single-walled nanotubes with distinct radii

We study the confinement of a C60 molecule encapsulated in a cylindrical nanotube as a function of the tube radius. Drawing the Mercator maps of the potential, we find two distinct molecular orientations; for tubes with small radii, RT < or approx. 7 A, a fivefold axis of the molecule coincides with the tube long axis, for larger radii, RT > or approx. 8 A, a threefold axis of the molecule coincides with the tube long axis. These different orientations are caused by the relative importance of the repulsive and the attractive parts of the van der Waals potentials of the molecule with the tube wall for small and large tubes respectively. Experimental evidence is provided by the apparent splitting of Ag modes of the C60 molecule in resonant Raman scattering