Physical Review Letters

Gap reduction and the collapse of solid C60 to a new phase of carbon under pressure

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We have studied solid C60, measuring the shift of the optical absorption edge with pressure to 35 GPa. In the range of 017 GPa, extrapolation of the absorption edge indicates that metallization should occur by 33 GPa. However, from 17 to 25 GPa an irreversible transition to a transparent phase occurs. Raman scattering of the depressurized sample shows no trace of C60, diamond, or graphite, indicating that the transition involves the collapse of the C60 molcules into a new structure of carbon. © 1992 The American Physical Society.