COMPRESSIBILITY, SPECIFIC-HEAT CAPACITY, AND GRUNEISEN-PARAMETER FOR C-60/C-70

We have measured the specific heat capacity c(p) of C60/C70 between 110 and 310 K and its compressibility kappa up to 1.1 GPa (11 kbar) at 293 K, a range in T and p which overlaps reported ranges of stability of both the rotationally disordered high T, low p fcc phase and the low T high p orientationally ordered sc phase. No sharp anomaly is observed in c(p) at the transition. The bulk modulus B near p = 0 was 8.4 GPa, rapidly increasing to about 16 GPa near 1 GPa. For our data, the intermolecular forces could be modeled by either a Lennard-Jones or a Born-Mayer potential, but this was not the case if literature data for compression vs. p were used.