Tetragonal polymerized phase ofC60

Experimental evidence of the existence of the polymerized tetragonal (T) phase of ${\mathrm{C}}_{60}$ as a stable high-pressure one is presented. Using different p,T paths of high-pressure–high-temperature treatment, phase T was obtained as a product of phase conversions of a monomeric fcc and two polymerized phases of ${\mathrm{C}}_{60}$ (including a rhombohedral one) at 2.2 GPa and 873 K. The dramatic differences in the rates of phase-T formation from monomeric and polymerized states of the system testified to the difference in the mechanisms of phase-T formation. The x-ray-diffraction pattern, IR, and Raman spectra of the almost pure phase T are presented.