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Reactions of xenon with iron and nickel are predicted in the Earth's inner core

Abstract

Studies of the Earth's atmosphere have shown that more than 90% of the expected amount of Xe is depleted, a finding often referred to as the ‘missing Xe paradox’. Although several models for a Xe reservoir have been proposed, whether the missing Xe could be contained in the Earth's inner core has not yet been answered. The key to addressing this issue lies in the reactivity of Xe with Fe/Ni, the main constituents of the Earth's core. Here, we predict, through first-principles calculations and unbiased structure searching techniques, a chemical reaction of Xe with Fe/Ni at the temperatures and pressures found in the Earth's core. We find that, under these conditions, Xe and Fe/Ni can form intermetallic compounds, of which XeFe3 and XeNi3 are energetically the most stable. This shows that the Earth's inner core is a natural reservoir for Xe storage and provides a solution to the missing Xe paradox.

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Figure 1: Chemical stabilities of Xe–Fe and Xe–Ni compounds.
Figure 2: Selected structures of predicted Xe–Fe compounds.
Figure 3: Electronic properties of XeFe3.
Figure 4: Phase diagram of Xe–Fe and Xe–Ni systems.

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Acknowledgements

The authors acknowledge support from the China 973 Program (2011CB808200), the Natural Science Foundation of China (grant nos 11274136, 11025418 and 91022029), the fund of CAEP-SCNS (R2014-0302), the 2012 Changjiang Scholars Program of China and the Changjiang Scholar and Innovative Research Team in University (IRT1132). Some calculations were performed in the High Performance Computing Center of Jilin University. C.J.P. was funded by the UK Engineering and Physical Science Research Council (EPSRC).

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Contributions

Y.M. proposed and coordinated the research. L.Z. and H.L. performed most of the calculations. L.Z., H.L., C.J.P., G.Z. and Y.M. analysed the data. C.J.P. carried out the Ab Initio Random Structure Searching structure predictions. All authors commented on the manuscript. L.Z. and Y.M. wrote the paper.

Corresponding author

Correspondence to Yanming Ma.

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The authors declare no competing financial interests.

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Zhu, L., Liu, H., Pickard, C. et al. Reactions of xenon with iron and nickel are predicted in the Earth's inner core. Nature Chem 6, 644–648 (2014). https://doi.org/10.1038/nchem.1925

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