Publication: Low viscosity of the Earth’s inner core
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2019-06-06
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Nature Publishing Group
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Abstract
The Earth’s solid inner core is a highly attenuating medium. It consists mainly of iron. The high attenuation of sound wave propagation in the inner core is at odds with the widely accepted paradigm of hexagonal close-packed phase stability under inner core conditions, because sound waves propagate through the hexagonal iron without energy dissipation. Here we show by first-principles molecular dynamics that the body-centered cubic phase of iron, recently demonstrated to be thermodynamically stable under the inner core conditions, is considerably less elastic than the hexagonal phase. Being a crystalline phase, the bodycentered cubic phase of iron possesses the viscosity close to that of a liquid iron. The high attenuation of sound in the inner core is due to the unique diffusion characteristic of the body-centered cubic phase. The low viscosity of iron in the inner core enables the convection and resolves a number of controversies.
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© The autors. Computations were performed using the facilities at the Swedish National Infrastructure for Computing (SNIC) located at the National Supercomputing Center in Linköping. The authors also wish to thank the Swedish Research Council (VR) for financial support (Grants 2013-5767, 2014-4750, and 2017-03744) and National Natural Science Foundation of China (Grant No. 11804175). A.B.B. and T.B. acknowledge support from Olle Engkvist Byggmästare Foundation. S.I.S. acknowledges the support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-MatLiU No. 2009 00971). M.M. acknowledges financial support by the Spanish Ministry of Economy and Competitiveness (CGL2013- 41860-P and CGL2017-86070-R).