A thermodynamic model of the rotational phase transition in solid C-60
is presented. The phase transition which appears at 257 K is a first-
order phase transition in which a competition occurs between entropy g
ain by rotation and energy gain by intermolecular attraction. The anom
aly in the specific heat, and the entropy and enthalpy changes observe
d at the critical temperature are well reproduced in the present numer
ical results.