X-ray diffraction study of the stacking faults in hexagonal C-70 single crystals

Pure C-70 crystallizes in close-packed crystal structures. Both the hexagonal close packing (h.c.p.) and the cubic close packing (c.c.p.) are known to exist. X-ray diffraction from single crystals with hexagonal habitus shows rods of diffuse intensity typical of stacking faults. The intensities of three of these rods were measured at room temperature with synchrotron radiation, and interpreted with a growth fault model assuming a depth of interaction of three layers. The result indicates the presence of both h.c.p. and c.c.p. domains, the former containing fewer stacking faults than the latter. The probability to find an h-stack of three layers (e.g., ABA) anywhere in the crystal is only about 60%.