Compressibility of C-60 in the temperature range 150-335 K up to a pressure of 1 GPa

We have measured the volume of nominally 99.9% pure C-60 as a function of pressure (p) in both the fee and sc phases up to 1 GPa over the temperature range 150 to 335 K using a highly accurate piston-and-cylinder technique. At zero pressure, the room-temperature bulk modulus B(0) is 6.8 GPa for the fee phase acid about 8.7-9.5 GPa for the sc phase. For Be latter phase, B(0) increases strongly with decreasing temperature to 10.4 GPa at 152 K and for both phases B increases rapidly with increasing pressure. The fcc-->sc transformation is always smeared over large ranges inp. Surprisingly, above 200 MPa B is lower in the sc phase than in the fee phase, which we explain as arising from molecular reorientation with increasing pressure. The formation of a mainly ''hexagon''-oriented, ordered phase above 0.6 GPa at low T gives rise to observable anomalies in B(p).