Orientationally ordered states in solid ${\mathrm{C}}_{60}$

We study the orientational ordering of the fullerene molecules in solid ${\mathrm{C}}_{60}$ with a phenomenological model proposed by Lu, Li, and Martin [Phys. Rev. Lett. 68, 1551 (1992)]. It is shown that the energy of a particular configuration is sensitive to the bond length of the fullerene molecule and there is an orientation that might explain the orientational disorders in solid ${\mathrm{C}}_{60}$. Also, the experimentally observed superstructure is investigated. Numerical calculations show that the orientational ordering of the fullerene molecules will induce structural deformation in the superstructure.