A PECULIAR DIFFRACTION EFFECT IN FCC CRYSTALS OF C-60

In the diffraction patterns of the f.c.c. phase of C60 the h00 (0k0 and 00l) reflections are consistently absent or very weak, even for the allowed reflections with h = even. It is shown how this phenomenon is sensitively related to the ratio of the molecular size and the lattice parameter. Hereby use is made of two different approaches: the Fourier transform method and an intuitive real space approach. More realistic models, than the uniformly thin shell model, considered till now, are treated. It is shown how the intensities of the h00 reflections vary in terms of the parameters of the model: shell radius, shell profile, as compared to the lattice parameter. The phenomenon is demonstrated on a single crystal fragment, using electron diffraction.