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Science 15 June 2007:
Vol. 316. no. 5831, pp. 1603 - 1605
DOI: 10.1126/science.1141374
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Reports

Origin of the Low Rigidity of the Earth's Inner Core

Anatoly B. Belonoshko,1,2* Natalia V. Skorodumova,3 Sergio Davis,1 Alexander N. Osiptsov,4 Anders Rosengren,2 Börje Johansson1,3,5

Earth's solid-iron inner core has a low rigidity that manifests itself in the anomalously low velocities of shear waves as compared to shear wave velocities measured in iron alloys. Normally, when estimating the elastic properties of a polycrystal, one calculates an average over different orientations of a single crystal. This approach does not take into account the grain boundaries and defects that are likely to be abundant at high temperatures relevant for the inner core conditions. By using molecular dynamics simulations, we show that, if defects are considered, the calculated shear modulus and shear wave velocity decrease dramatically as compared to those estimates obtained from the averaged single-crystal values. Thus, the low shear wave velocity in the inner core is explained.

1 Applied Materials Physics, Department of Materials Science and Engineering, The Royal Institute of Technology, SE-100 44 Stockholm, Sweden.
2 Condensed Matter Theory, AlbaNova University Center, Department of Theoretical Physics, The Royal Institute of Technology, SE-10691 Stockholm, Sweden.
3 Condensed Matter Theory Group, Department of Physics, Uppsala University, Uppsala Box 530, Sweden.
4 Institute of Mechanics, Moscow State University, 142432 Moscow, Russia.
5 School of Physics and Optoelectronic Technology and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, China.

* To whom correspondence should be addressed. E-mail: anatoly.belonoshko{at}fysik.uu.se

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Stability of body-centered cubic iron-magnesium alloys in the Earth's inner core.
K. Kadas, L. Vitos, B. Johansson, and R. Ahuja (2009)
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Elastic Anisotropy of Earth's Inner Core.
A. B. Belonoshko, N. V. Skorodumova, A. Rosengren, and B. Johansson (2008)
Science 319, 797-800
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