Solid C₆₀: Pressure Induced Phase Transitions

Based on in situ high pressure x-ray diffraction with diamond anvil cell by using synchrotron radiation and pressure-quench x-ray measurement, phase transition of C₆₀ under high pressured is studied. The maximum pressure used is 30GPa in quasi-hydrostatic case but 44GPa in nonhydrostatic case. At ambient pressure, C₆₀ crystal is a fcc phase with lattice parameter a=14.2086Å. It transforms from fcc to a lower symmetry phase at pressure of 13.7GPa, and then transforms to an amorphous state under pressure up to 25-30 GPa. This amorphous state is metastable at normal condition. Finally, the experimental results are discussed.