Identification of the polymerized orthorhombic phase of C60 fullerene

It is established by x-ray diffraction and Raman scattering that the polymerization of C₆₀ fullerene at 1.5 GPa and 723 K leads to the formation of an orthorhombic phase that is different from the previously identified high-pressure orthorhombic phase. It is determined by a calculation of the optimal packing of linear C₆₀ polymers by the method of atom-atom potentials that the energetically favorable structure of the orthorhombic phase belongs to the space group P n n m and not the previously proposed group I m m m. The computed value of the rotation angle of the polymer chains that corresponds to the minimum packing energy was equal to 61°. The mechanisms leading to the formation of the polymerized phases are discussed on the basis of the results obtained. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 2, 110–114 (25 July 1997)