The crystal-field potential of solid C-60 at room temperature

Bragg intensities from neutron diffraction data for C-60 single crystals we re used to determine the rotational potential V(w) at room temperature. The rotational potential is evaluated in terms of mixed rotator functions M. T he expansion coefficients v(l)(is an element of), i.e. potential parameters , are obtained directly from experiment. The potential exhibits well develo ped minima, absolute ones at the Euler angle set w(1) and relative ones at w(2). They correspond to the two orientations, i.e, pentagonal and hexagona l facing, of the molecules in their low-temperature arrangement. The overal l potential barrier height of the-absolute minimum is 400 K and the differe nce between the two types of minima is 270 K.