BULK C60 (fullerite) is a solid composed of extremely hard pseudospherical molecules bonded by weak van der Waals interactions. We expect that pressurization will probe this diversity as the intermolecular distance is reduced. Here we present experimental measurements of the room-temperature pressure-volume equation of state of C60 fullerite to pressures of 20 GPa. The face-centred cubic phase remains stable under hydrostatic compression to this pressure, with an atmospheric-pressure isothermal bulk modulus of K0 = 18.1 ± 1.8 GPa and dK0/dP = 5.7 ± 0.6, characteristic of isotropic van der Waals intermolecular bonding. X-ray diffraction intensity changes are consistent with the compressibility of the C60 molecule being significantly lower than that of the bulk fullerite solid. Under non-hydrostatic compression, a transition to a crystallographic structure of lower symmetry is observed at 16±1 GPa.
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