Pressure-induced polymerization of fullerenes: a comparative study of C₆₀ and C₇₀

Abstract

To investigate the polymerization of fullerenes, solid C₆₀ and C₇₀ have been subjected simultaneously to high pressures and temperatures, with pressures up to 7.5 GPa and temperatures up to 800 °C. X-ray-diffraction measurements indicate that the FCC solid C₆₀ transforms to an orthorhombic structure consisting of a polymerized linear chain of C₆₀ molecules. The associated changes in the intramolecular vibrational modes have been probed through Raman and Infrared measurements. In contrast to solid C₆₀, under similar conditions, polymerization is not observed in the case of solid C₇₀, although there is a structural transition from the initial hcp structure to a Rhombohedral structure. This lack of polymerization in C₇₀ is discussed in terms of the structure of solid C₇₀ under high pressure and temperature conditions, coupled with the topochemical features of the C₇₀ molecule.