DI42A-08
Synthesis of Xenon and Iron/Nickel Intermetallic Compounds Under the Thermodynamic Conditions of the Earth's Core.

Thursday, 17 December 2015: 12:05
303 (Moscone South)
Elissaios Stavrou1, Joseph M Zaug1, Jonathan Crowhurst1, Sergey Lobanov2, Alexander F Goncharov3, Vitali Prakapenka4, Clemens Prescher5, Yansun Yao6, Hanyu Liu3 and Zurong Dai1, (1)Lawrence Livermore National Laboratory, Livermore, CA, United States, (2)GL Carnegie Institution of Washington, Washington, DC, United States, (3)Carnegie Institution for Science Washington, Washington, DC, United States, (4)University of Chicago, Chicago, IL, United States, (5)University of Chicago, Center for Advanced Radiation Sources, Chicago, IL, United States, (6)University of Saskatchewan, Department of Physics and Engineering Physics, Saskatoon, SK, Canada
Abstract:
The lower Xe abundance in Earth's atmosphere, in comparison to other noble gases like Ar and Kr, is one of the most challenging open questions in geosciences [1]. The origin of the so-called "missing Xe paradox" is usually attributed to the inclusion of Xe in the interior of Earth[2]. Although Xe is known to form compounds (e.g. with hydrogen, oxygen), none of them can be related with Earth's interior. Indeed, only a very low amount of Xe can be incorporated in silica at <1 GPa and 500K [3]. On the other hand, experimental attempts have failed to trace possible formation of Fe-Xe compounds up to 155 GPa and bellow 2500K [4]. A very recent theoretical study, suggests that Xe-Ni and Xe-Fe compounds can form at thermodynamic conditions representative of Earth's outer core [5].

Here we explored the possible formation of stable compounds in the Xe-Fe/Ni system at thermodynamic conditions representative of Earth's outer core starting from the following mixtures: a) Xe-Fe, b) Xe-Ni and c) Xe and an Fe/Ni alloy representative of Earth’s core (ca 6% Ni). Using in situ synchrotron X-ray diffraction and Raman spectroscopy we report the formation of: a) a XeNi3 compound, in the form of a CrNi3-type FCC solid solution, above 150 GPa and 1500K, b) a Xe(Fe/Ni)3 compound, tentatively characterized as an orthorhombic NbPd3-type solid solution, above 190 GPa and 2000K and c) a still not completely characterized XeFexcompound above 180 GPa and 2000K. This work provides a plausible explanation of the "missing Xe paradox”, and underscores the importance of understanding the novel rules of high-pressure chemistry for an improved understanding of the structure and chemistry of the Earth’s core.

[1] E. Anders, E. and T. Owen, Science 198, 453 (1977).

[2] Caldwell, W. A. et al.,Science 277, 930 (1997).

[3] C. Sanloup et al.,Science 310, 1174(2005).

[4] D. Nishio-Hamane et al.,Geophys. Res. Lett. 37, L04302 (2010).

[5] L. Zhu et al., Nature chemistry 6, 664 (2014).

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