Pressure-induced cross-linking of C₆₀

We show that fee C₆₀ is converted to at least two different structures by high temperature and pressure. These new phases are stabilized by temperature-quenching. The synthesis condition of P=5GPa and 300°C<T<400°C produces an fee structure with a lattice constant of a₀=13.6Å which is 3.7% smaller than that of pristine fee phase. At P=5GPa and 500°C<T<800°C, a rhombohedral phase of a=9.77Å and α=56.3° are stabilized. In these structures, the intermolecular distances are significantly smaller than the pristine phase. A cross-linking of C₆₀ molecules is proposed based on the symmetry reduction shown by several spectroscopic data. These new phases are metastable and reverts to the conventional fee C₆₀ by heating up to 300°C at ambient pressure.