In situ high-pressure synchrotron X-ray diffraction and Raman spectroscopic experiments of scottyite, BaCu2Si2O7, were carried out in a diamond anvil cell up to 21 GPa at room temperature. X-ray diffraction patterns reveal four new peaks near 3.5, 3.1, 2.6 and 2.2 Å above 8 GPa, while some peaks of the original phase disappear above 10 GPa. In the Raman experiment, we observed two discontinuities in dν/dP, the slopes of Raman wavenumber (ν) of some vibration modes versus pressure (P), at approximately 8 and 12 GPa, indicating that the Si-O symmetrical and asymmetrical vibration modes change with pressure. Fitting the compression data to Birch–Murnaghan equation yields a bulk modulus of 102 ± 5 GPa for scottyite, assuming Ko′ is four. Scottyite shows anisotropic compressibility along three crystallographic axes, among which c-axis was the most compressible axis, b-axis was the last and a-axis was similar to the c-axis on the compression. Both X-ray and Raman spectroscopic data provide evidences that scottyite undergoes a reversible phase transformation at 8 GPa.
Multiferroic CuCrO2 under high pressure: In situ X-ray diffraction and Raman spectroscopic studies