Determination of molecular orientational angles in the low-temperature phase of C-60

The low-temperature structure of C-60 is simple cubic, however, orientational long-range order is far from being complete. According to current understanding C-60 molecules can adopt two orientational states obtained by rotations about [1 1 1] axes through angles close to 98 degrees and 38 degrees. We present results of an elastic diffuse neutron-scattering investigation being clearly incompatible with these values and yielding rotational angles close to 102 degrees and 42 degrees instead, The significance of this finding is the following : While the previous angles can be interpreted as an attempt to reconcile icosahedral molecular symmetry with long-range cubic lattice symmetry the new angles can be understood as the result of an optimized arrangement of nearest-neighbor molecules, The molecular orientational states, therefore, are indicative of the dominant role of short-range interactions in this system.