Structural features of the polymer-like phase of AC60 fullerides

A new approach is proposed for describing the deformation of the C₆₀ molecule in the polymer-like phase of the fullerides AC₆₀ (A=K, Rb). A discrete basis of orientational states of the molecule is introduced, and orientational ordering is described on the basis of a phenomenological theory. A symmetry analysis of the molecular vibrations in the Fm3m phase is performed. It is shown that small rotations of the C₆₀ can occur at a phase transition. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 2, 110–115 (25 July 1996)