Raman study of pressure-induced structural change in C6I6 up to 47 GPa - art. no. 064104

The pressure change in the frequencies of intramolecular vibrational modes in hexaiodobenzene (C6I6) has been investigated by Raman scattering measure ments at room temperature under pressure up to 47 GPa with a diamond anvil cell. An out-of-plane vertical vibration mode of carbon born structure prod uces mode softening by loading up to 13 GPa in spite of mode-hardening occu rring in the other three modes related to the in-plane vibrations. This res ult is consistent with the molecular deformation observed by previous high pressure x-ray diffraction. The structure of the spectrum is obliterated wi th a further rise in pressure beyond 13 GPa due to an increase in the absor ption of an excitation laser light. Raman peaks reappear at pressures below 4 GPa by releasing the pressure from 47 GPa; however, these peaks are loca ted at different frequency regions from the original positions, indicating that molecular dissociation takes place during the pressure release.