Reversible pressure-induced amorphization in solid C₇₀: Raman and photoluminescence study

Abstract

We have studied single crystals of C₇₀ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broadband similar to that of the amorphous carbon without any trace of the Raman lines of C₇₀. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting C₇₀ crystal. These results indicate that the C₇₀ molecules are stable up to 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid C₆₀. A qualitative explanation is suggested in terms of intermolecular versus intramolecular interactions.