Orientational phase transitions in a C70 crystal at high pressure
Maksimov A. A. , Meletov K. P. , Osip'yan Yu. A. , Tartakovskii I. I. , Artemov Yu. V. , Nudel'man M. A.
The Raman spectra of C70 crystals have been studied at pressures up to 17 GPa. The frequency Ω of most of the optical vibrations increases linearly with the pressure P. The pressure-induced shift dil/Äò itself has jumps at P\^2±0.2 and P2^5.5±0.5 GPa. The jumps observed in ÄûÄ Pare correlated with a sharp change in the half-width of the Raman line for several optical modes. These spectral features 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.