Abstract
It is well established that a significant amount of heat produced in the Earth’s mantle is due to the decay of uranium. However, uranium cannot be incorporated in large amounts into the most common mantle minerals. Here, we suggest that carbonates could be host phases for uranium in carbon-rich mantle lithologies. Two anhydrous uranium carbonates, U2[CO3]3 and U[CO3]2, were simultaneously synthesized by a reaction of UO2 with CO2 in a laser-heated diamond anvil cell at 20(1) GPa and 1800(200) K. Their crystal structures were obtained from synchrotron-based single crystal diffraction data and reproduced by density functional theory-based calculations. In U2[CO3]3 trivalent uranium cations are present, while uranium is four-valent in U[CO3]2. The synthesis of U2[CO3]3 and U[CO3]2 is a significant extension of the chemistry of uranium compounds and we provide a straightforward synthesis route for a UIII-containing compound.
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Data availability
The X-ray crystallographic coordinates for the structure reported in this study has been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition numbers 2475926 (U[CO3]2) and 2475927 (U2[CO3]3). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. The supplementary material contains additional information to the results of the single crystal structure determination and DFT-based calculations.
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Acknowledgements
We gratefully acknowledge funding from the DFG (WI1232 and BA4020) and the BMBF (02NUK060).E.B. and M.B. acknowledge the support of the DFG Emmy-Noether Program (projects BY101/2-1 and BY112/2-1) and the Johanna-Quandt-Stiftung. M.B. acknowledges the support by the LOEWE program. B.W. is grateful for support by the Dassault Systémes Science Ambassador program. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III, beamline P02.2.
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D.S., L.B., G.L.M., and P.K. performed experiments. V.M. and B.W. performed DFT calculations. N.G.managed the synchrotron beam line. B.W., E.B. and M.B. supervised the project.
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Spahr, D., Bayarjargal, L., Bykova, E. et al. High-pressure synthesis of U2[CO3]3 and U[CO3]2 as potential host phases for uranium in the Earth’s mantle. Commun Chem (2026). https://doi.org/10.1038/s42004-026-01911-0
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DOI: https://doi.org/10.1038/s42004-026-01911-0
