STRUCTURAL-PROPERTIES OF VAPOR-GROWN C(60) CRYSTALS

Vapor grown crystals of C60 with thin flat triangular, rhombic or trapezoidal shapes of size to 1 x 2 x approximately 0.001 mm as well as prismastic crystals typically 0.5 x 0.4 x 0.2 mm have been grown using a high temperature vapor transport method. Room temperature X-ray precession photography shows these crystals exhibit diffraction patterns consistent with those for either (a) single or (b) twinned crystals of the previously reported face-centered cubic structure or (c) a more complex cell of hexagonal symmetry with a=10.010(2) angstrom and c=49.064(11)angstrom. This latter form actually is a multiple twin containing both the face-centered cubic and the close-packed hexagonal structure types. The sharp diffraction maxima for either the single or the twinned crystals demonstrate that they consist of large coherent domains and are essentially free of planar defects parallel to the twin planes.