SINGLE-CRYSTAL STRUCTURE OF C-60 AT 300-K - EVIDENCE FOR THE PRESENCE OF OXYGEN IN A STATICALLY DISORDERED MODEL

The structure of solvent-free single crystals of sublimed C-60 has been analysed at 300 K by X-ray diffraction. A unique solution of atom coordinates gave a satisfactory agreement with the intensity data. This indicates that the C-60 balls exhibit a time-averaged preferred position in the crystals which are, however, heavily affected by rotational disorder. The structure reveals the truncated icosahedral molecular shape with two sets of carbon-carbon bond distances. Contour plots indicate the anisotropic distribution of electron density within the almost perfectly spherical shell of the molecule. The analytically pure crystals contained an impurity of molecular oxygen located statistically over some hexagons of each 'buckyball' resulting in a limiting stoichiometry of C-60 O-2.