Structure and density of Fe-C liquid alloys under high pressure

G. Morard, Y. Nakajima, D. Andrault, D. Antonangeli, A. L. Auzende, E. Boulard, S. Cervera, A. N. Clark, O. T. Lord, J. Siebert, V. Svitlyk, G. Garbarino, M. Mezouar

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The density and structure of liquid Fe-C alloys have been measured up to 58 GPa and 3200 K by in-situ X-ray diffraction using a Paris-Edinburgh press and laser-heated diamond anvil cell. Study of the pressure evolution of the local structure inferred by XRD measurements is important to understand the compression mechanism of the liquid. Obtained data show that the degree of compression is greater for the first coordination sphere than the second and third coordination spheres. The extrapolation of the measured density suggests that carbon cannot be the only light element alloyed to iron in the Earth's core, as 8−16 at%C (1.8−3.7 wt%C) would be necessary to explain the density deficit of the outer core relative to pure Fe. This concentration is too high to account for outer core velocity. The presence of other light elements (e.g., O, Si, S and H) is thus required.
Original languageEnglish
Pages (from-to)7813-7823
Number of pages11
JournalJournal of Geophysical Research: Solid Earth
Issue number10
Early online date19 Oct 2017
Publication statusPublished - 27 Nov 2017


  • Composition of the planets
  • Experimental mineralogy and petrology
  • High-pressure behavior
  • X-ray, neutron and electron spectroscopy and diffraction
  • liquid density
  • Earth's core
  • light elements


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