PRESSURE-INDUCED CROSS-LINKING OF C-60

We show that fcc C-60 is converted to at least two different structure s by high temperature and pressure. These new phases are stabilized by temperature-quenching. The synthesis condition of P=5GPa and 300 degr ees C<T<400 degrees C produces an fcc structure with a lattice constan t of a(0)=13.6 Angstrom which is 3.7% smaller than that of pristine fe e phase. At P=5GPa and 500 degrees C<T<800 degrees C, a rhombohedral p hase of a=9.77 Angstrom and alpha=56.3 degrees are stabilized. In thes e structures, the intermolecular distances are significantly smaller t han the pristine phase. A cross-linking of C-60 molecules is proposed based on the symmetry reduction shown by several spectroscopic data. T hese new phases are metastable and reverts to the conventional fcc C-6 0 by heating up to 300 degrees C at ambient pressure.