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Science 29 June 2007:
Vol. 316. no. 5833, pp. 1880 - 1883
DOI: 10.1126/science.1142105
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Reports

Body-Centered Cubic Iron-Nickel Alloy in Earth's Core

L. Dubrovinsky,1 N. Dubrovinskaia,2 O. Narygina,1 I. Kantor,1 A. Kuznetzov,3 V. B. Prakapenka,3 L. Vitos,4,5,6 B. Johansson,4,5 A. S. Mikhaylushkin,6,7 S. I. Simak,7 I. A. Abrikosov7

Cosmochemical, geochemical, and geophysical studies provide evidence that Earth's core contains iron with substantial (5 to 15%) amounts of nickel. The iron-nickel alloy Fe0.9Ni0.1 has been studied in situ by means of angle-dispersive x-ray diffraction in internally heated diamond anvil cells (DACs), and its resistance has been measured as a function of pressure and temperature. At pressures above 225 gigapascals and temperatures over 3400 kelvin, Fe0.9Ni0.1 adopts a body-centered cubic structure. Our experimental and theoretical results not only support the interpretation of shockwave data on pure iron as showing a solid-solid phase transition above about 200 gigapascals, but also suggest that iron alloys with geochemically reasonable compositions (that is, with substantial nickel, sulfur, or silicon content) adopt the bcc structure in Earth's inner core.

1 Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany.
2 Mineralogical Institute, Heidelberg University, Im Neuenheimer Feld 236 D-69120 Heidelberg, Germany.
3 Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, USA.
4 Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Brinellvägen 23, SE-100 44, Stockholm, Sweden.
5 Condensed Matter Theory Group, Department of Physics, Uppsala University, Box 530, SE-75121 Uppsala, Sweden.
6 Research Institute for Solid State Physics and Optics, Post Office Box 49, H-1525 Budapest, Hungary.
7 Department of Physics, Chemistry, and Biology, Linköping University, SE-58183 Linköping, Sweden.

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