The dielectric properties of C60 have been measured as functions of temperature
and hydrostatic pressure in the ranges 80–370 K and 0–0.8 GPa. The results show
sharp anomalies at the rotational transition above 260 K and large relaxation
peaks associated with the rotational ‘glass transition’. From the measured
frequencies of the loss peaks we calculate the energy barrier for molecular jumping
between the ‘pentagon’ and ‘hexagon’ molecular orientations. The energy barrier
increases by 13% GPa−1.