In situ Raman study of C60 polymerization at high pressure high temperature conditions

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Abstract
C 60 polymerization was studied in situ by Raman spectroscopy in the pressure range 10–27 GPa and temperatures up to 830 K. Quenched samples were studied by XRD using synchrotron radiation. Below 18 GPa only one- and two-dimensional polymers were found to form during heating. During slow cooling and pressure release, only the relative amounts of the different phases were changing. The structure of the 10–18 GPa samples after quenching is rhombohedral. The observed polymerization pathway suggests a gradual increase of the polymerization which occurs in the following sequence monomers→dimers→chains→tetra-coordinated polymer→hexa-coordinated polymer. Above 18 GPa the in situRaman spectra during heating remained almost unchanged. XRD of the quenched samples revealed that they have a cubic structure with cell parameter above 13 Å. The sample heated at 27 GPa showed elliptical Debye–Scherrer diffraction ring due to the strong anisotropic deformation. No very dense phases reported in previous studies (so called “superhard fullerite”) were observed.