Towards Pressure Triggered Phase Transition, an Experimental Observation of Charge Density Redistribution in Gypsum

Gypsum CaSO4·2H2O is one of the most common hydrated minerals in Earth’s crust. In this project we focus on the high pressure (>4 GPa) phase transition to gypsum-II to experimentally determine quantitative charge density redistribution. The use of quantum crystallography offers a better understanding of interactions within the crystal and its energetic properties. Multipole density model refinement demands excellent quality of single-crystal XRD data, characterized by high resolution and completeness. Moreover, Diamond Anvil Cell (DAC) restricts access to reciprocal space and introduces experimental noise.
ID-27 at ESRF offers exceptional solutions, very well collimated X-ray beam, extra stabilisation of the whole data collection system, excellent detector, high brilliance of the beam. These factors effectively address all the experimental challenges. Proposed research will enhance the role of quantum-crystallography in Earth and material sciences at high pressure.