Neutron diffraction study of the structure of deuterated and fluorinated fullerene C-60

Synthesized C60F48 fluoride and C60D8, C60D18 and C60D36 deuterides of full erene C-60 are described. All the compounds have a f.c.c. structure (like t he original C-60)with periods a = 1.726, 1.423, 1.448, and 1.498 nm, respec tively. 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 s hells inside the molecule and van der Waals bonds between the peripheral at oms of one molecule and neighbor molecules. The description of the structur e 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 w ith the neighbor molecule. The low-temperature behavior of the C60F48 and C 60D36 compounds is studied. A phase transformation in the C60F48 fluoride a t T=270 K is described, which is similar to the transformation of an orient ation type in isostructural fullerene C-60 at a close temperature. The obse rved changes in the intensities of the diffraction peaks are described unde r the assumption that the phase transformation is accompanied by a decrease in the volume at invariable radii of the carbon and fluorine spheres. Simi lar changes in the intensity have been determined in the C60D36 compound.