X-ray study of pressure-collapsed fullerite

X-ray-diffraction studies are described for a new phase of carbon called collapsed fullerite (CF) that was produced by application of high pressure to fullerite (${\mathrm{C}}_{60}$). At ∼20 GPa there is an irreversible transition to a phase that has neither the (111) Bragg peak of diamond nor any of the Bragg peaks associated with the fcc phase of ${\mathrm{C}}_{60}$. The spectrum of CF is flat and featureless in the range of study.