Vibrational properties of SnGeS3 under high pressure

We measured Raman spectra of SnGeS3 single crystal under hydrostatic pressu re up to 19.5 GPa. Fourteen of the seventeen modes observed at low pressure s disappear around 7 GPa. The remaining three modes persist up to 11.5 GPa. No scattering activity is found above 19.5 GPa. All these changes, as well as color changes, are reversible. The intensities of the Raman modes of Sn GeS3 were calculated using valence-force-field and a bond polarizability mo del. Ve have shown that the interchain interaction is responsible for the i ntensity exchange of 346 cm(-1) and 364.5 cm(-1) modes under pressure. An a ssignment to internal and external modes is also proposed.