MEAN-FIELD THEORY FOR C-70

Orientational ordering transitions in C-70 are studied by constructing a Landau free energy in terms of order parameters describing long-ran ge orientational order. This theory predicts that the transition from the orientationally disordered state into a partially ordered state, w here the long axes of the molecules are parallel to one another, is di scontinuous with an elastic distortion. Order parameters describing th e lower temperature transition, where spinning about the long axis bec omes hindered, are also discussed.