M.I.E. thanks the Max Planck Society and the MPI for Chemistry for support, U. Pöschl for encouragement, R. Wittkowski and the staff of the mechanical workshop of the MPI for Chemistry for technical support. We thank S. Sutton for discussion. L.B. is supported by DOE-BES through award DE-SC0002613. S.M. acknowledges support from the FSU Provost Postdoctoral Fellowship Program. The National High Magnetic Field Laboratory acknowledges support from the US NSF Cooperative Grant number DMR-1644779 and the state of Florida. Portions of this work were performed at GeoSoilEnviro CARS (The University of Chicago, Sector 13), Advanced Photon Source (APS), Argonne National Laboratory. GeoSoilEnviro CARS is supported by the National Science Foundation – Earth Sciences (EAR – 1634415) and Department of Energy – GeoSciences (DE-FG02-94ER14466). This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract number DE-AC02-06CH11357.

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Nature thanks James J. Hamlin and the other anonymous reviewer(s) for their contribution to the peer review of this work.