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.