High pressure studies have diverse applications of direct interest to Australia, ranging from mineralogical and petrochemical research to molecular biology and food technology to the development of novel electronic materials. Studying the response of different materials to applied pressures has important implications in the understanding of corrosion mechanisms under pressure and stress, processes which are of great importance to Australia's primary industries. Investigation of high pressure synthesis, pressure tuning and selection of preferential reaction paths in the absence of solvents or catalysts, are fundamental to the field of "green chemistry". Amorphization and changes in coordination at high pressure, study of phase changes and pressure- and temperature-induced changes occurring in the structure of proteins are further uses of the high pressure technique. There is however little experience within Australia at studying materials at elevated pressures with (10 GPa and above) infrared light, and this project has began to address this.
Mark Tobin and Ljiljana Puskar, beamline scientists of the Infrared beamline at the Australian Synchrotron, have carried out their first high pressure IR studies at the SMIS beamline, assisted by Jean Paul Itié and Paul Dumas, from SOLEIL.. These studies have primarily aimed at providing experience for the Australian Synchrotron IR beamline team, through the study of several minerals, some of which have been well characterized in the infrared region, and some which have not been previously studied in this regime. Samples including Talc [Si₄O₁₀](OH), Calcite CaCO₃, Stichtite [Mg₆Cr₂(OH)₁₆](CO₃).4H₂O, Witherite (BaCO3) the zeolite Heulandite (Ca,Na₂,K₂)₄[Al₈Si₂₈O₇₂].24H₂O, have been studied during the 5 days of synchrotron beam. 

From left to right: J.P. Itie ( SOLEIL), Mark Tobin ( Australian Synchrotron), P. Dumas ( SOLEIL) and Ljiljana Puskar ( Australian Synchrotron) at the NICPLAN end station at SMIS.	The Diamond Anvil Cell (DAC) used in this study.
Pressure dependency of several mid-IR vibrational bands of the witherite. The observed upward and downward frequency shifts will help to understand the structural evolution of this component under pressure.

The spectra were recorded using the NICPLAN microscope at the SMIS beamline, using an MCT broadband detector. An x15 objective was used in this study, providing a spot size at the sample of about 12x12 μm².
Several vibrational bands were observed to move in opposite direction, as shown in the figure below. There is a marked spectral change occurring above 8.1 GPa, which arises from a phase transition induced by the pressure.

This will help the authors of this work to better understand the structural evolution of this component under pressure.