An internal-friction study of C60 crystal intercalated with O2

After a C-60 crystal was intercalated with O-2, the internal-friction peak due to the orientational relaxation of the C-60 molecules shifted to a lower temperature. Also, the activation energy decreased, by 26 meV. These results indicate that the depth of the orientational potential well is changed by the O-2 intercalation. This change is assumed to be due to the electrostatic interaction between O-2 and C-60 molecules. The decrease of the order-disorder phase transition temperature, which is by about 20 K, can also be explained using this model.