Raman Study of Phase Transitions in C70 Crystal at High Pressure

Abstract

Abstract The Raman spectra of C70 single crystals have been measured at pressures up to 17 GPa. The frequency ω of most of the optical intramolecular phonons increases linearly with pressure P. The slope of the pressure shift dω/dP itself has jumps at 2±0.2 and 5.5±0.5 GPa. These jumps are correlated with a sharp change in the half-width of the Raman line for several optical modes. The peculiarities of the Raman scattering are linked with phase transitions caused by an orientational ordering of the C70 molecules in the crystal lattice as the pressure is raised.