Abstract:

The interactions between C60 molecules in solid state are calculated by the potential model (exp-6-1). The states of C6o molecules in solid are given at room temperature and at lower temperature. C60 molecule rotates rapidly at room temperature; the rotation rate decreases and the rotational axes tend to ordering as temperature becomes lower. And at about 260K the structure undergoes a first-order phase transiton from the high-temperature FCC phase to the ordered SC structure. The molecule equivalence above 260K is now broken by rorating the four molecules through the same angle but around different <111> axes: the molecule at (0,0,0) around [111], that at (1/2,1/2,0) around [111], that at (0,1/2,1/2) around [111] and at (1/2,0.1/2) around [111]. At about 90K, the system undergoes a second-order phase transition-----glass transition.

Key words: C₆₀, Phase transition, (exp-6-1)potential model, Orientational transition