Phase Transition in Hemimorphite Under High Pressure by Applying Experimental Quantitative Charge Density Studies

We will study the nature of phase transition (PT) in a mineral called hemimorphite - Zn4(Si2O7)(OH)2xH2O under pressure, which crystallises in the orthorhombic crystal system. It exhibits PT from Imm2 to Pnn2 between ca. 2.6-3.1 GPa. We want to study this PT at the level of quantitative redistribution of experimental electron density and quantitatively characterize how atoms/ions exchange electron density under pressure, how existing interatomic interactions are weakened and new interactions are unset. To achieve our aims, we will apply the X-ray beam with at least ca. 50keV (or higher), wide opening diamond anvil cell (for exampl.: Diacell120 and our membrane 90o opening angle cell or use the cells which are available at ESRF. We will use 2-3 pieces of crystals inside DAC, and collect 100% (or close to 100%) completeness up to the resolution close to 0.4 (or better) Å. Then will refine multipole model of electron density against experimental variable pressure X-ray data.