Understanding the Stability of Uranyl Cations ([UO2]2+) at Elevated Pressures

The aim of this proposal is to conduct a systematic study on the chemical stability of abundant uranyl-compounds (such as carbonates and nitrates) up to 100 GPa and 3000 K using single-crystal X-ray diffraction (XRD) in diamond anvil cells (DACs). We propose to investigate i) the thermal stability of simple uranyl carbonates (UO2CO3) and uranyl nitrates (UO2(NO3)2), and ii) the chemical reactivity between uranium oxide (UO2) with CO2/N2O under the same p,T-conditions. Through this combined approach, we expect to determine the phase stability regions of the phases belonging to U-O-C and the U-O-N systems, and complement the results with Raman spectroscopy and DFT calculations. In addition, we aim to provide the first structure description of an actinide sp3-carbonate, which we prior identified in our experimental Raman data.