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.