Structural study of HNO3-H2O system at pressures up to 100 GPa

The high-pressure phase diagram of the H-N-O system is essential for understanding processes in the interiors of ice giant planets such as Neptune and Uranus. Despite theoretical predictions on stabilization of various H-N-O compounds under high pressure, including H3NO4 polymorphs, the HNO3-H2O system remains completely unexplored experimentally.
Here, we propose a multigrain single-crystal X-ray diffraction (m-SCXRD) study of the HNO3-H2O system up to 100 GPa to obtain crystal structures of high-pressure H-N-O phases at ID11 beamline. The aims of the proposed experiments are (1) a synthesis of novel H-N-O compounds at pressure up to 100 GPa, (2) characterization of their crystal chemistry, (3) study their behavior upon decompression, (4) test theoretical predictions, and (5) search for regularities in high-pressure chemistry of the fundamental H-N-O system.