Molecular interaction and crystal packing in products of polymerization offullerene C-60 under high pressures

The optimum packings in the products of polymerization of fullerene C-60-li near chains and planar layers with the tetragonal and hexagonal structures- formed under high pressures as the orthorhombic (O), tetragonal (T), and rh ombohedral (R) crystalline phases, respectively, are computed within the fr amework of the atom-atom potential method. The computation provided a more detailed description of these phases than the earlier description (Nunez-Re gueiro et al., 1995) with ambiguous orientations of C-60 cages. Thus, in th e O phase, the optimum rotation angle of the polymer chain about its axis i s 60 degrees, which indicates the sp. gr. Pnnm. In the T phase, the packing of tetragonal layers with each of the subsequent layers being rotated by 9 0 degrees with respect to the previous one (sp. gr. P4(2)/mmc) provides the energy gain in comparison with the packing based on the translation of a l ayer toward the center of the volume (sp. gr. Immm). Finally, in the R phas e, two variants of the layer packing are determined, of which the energy-ad vantageous packing is described for the first time.