Tetragonal polymerized phase of C-60

Experimental evidence of the existence of the polymerized tetragonal (T) ph ase of 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 fee and two polymerized phas es of C-60 (including a rhombohedral one) at 2.2 GPa and 873 K. The dramati c differences in the rates of phase-ir formation from monomeric and polymer ized states of the system testified to the difference in the mechanisms of phase-ir formation. The x-ray-diffraction pattern, TR, and Raman spectra of the almost pure phase T are presented. [S0163-1829(98)02441-2].