Neutron diffraction study of the structure of deuterated and fluorinated fullerene C60

Synthesized C60F48 fluoride and C60D8, C60D18 and C60D36 deuterides of fullerene C-60 are described. All the compounds have a f.c.c. structure (like the original C-60)with periods a = 1.726, 1.423, 1.448, and 1.498 nm, respectively. Powder neutron diffraction diagrams are described on the basis of a double-shell model, i.e., an internal carbon sphere with a radius of 0.356 nm and a fluorine or deuterium sphere with a radius of 0.530 or 0.470 nm, respectively. The structure of the fluorinated and deuterated fullerenes is discussed with allowance for the existence of covalent bonds between the shells inside the molecule and van der Waals bonds between the peripheral atoms of one molecule and neighbor molecules. The description of the structure of the fullerene derivatives is based on the assumption that deuterium or fluorine atoms are absent on the external shell in the places of contact with the neighbor molecule. The low-temperature behavior of the C60F48 and C60D36 compounds is studied. A phase transformation in the C60F48 fluoride at T=270 K is described, which is similar to the transformation of an orientation type in isostructural fullerene C-60 at a close temperature. The observed changes in the intensities of the diffraction peaks are described under the assumption that the phase transformation is accompanied by a decrease in the volume at invariable radii of the carbon and fluorine spheres. Similar changes in the intensity have been determined in the C60D36 compound.