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地球与行星物理

ISSN  2096-3955

CN  10-1502/P

Citation: Wei Zhang, Mei Tang, ZhenWei Niu, 2022: The anisotropy of hcp iron under inner core conditions: the effect of light elements, Earth and Planetary Physics. http://doi.org/10.26464/epp2022035

doi: 10.26464/epp2022035

The anisotropy of hcp iron under inner core conditions: the effect of light elements

Wei Zhang 1,, Mei Tang 2,, ZhenWei Niu 1,3*,,

1 Laboratory for Extreme Conditions Matter Properties, Southwest University of Science and Technology, Mianyang 621010, China;

2 Fundamental Science on Nuclear Wastes and Environmental Safety Laboratory, Southwest University of Science and Technology, Mianyang 621010, China;

3 School of National Defense Science & Technology, Southwest University of Science and Technology, Mianyang 621010, China

Corresponding author: ZhenWei Niu,

Fund Project: The authors are grateful to the editors and reviewers for their valuable comments, which helped to improve the original manuscript. This work is supported by the National Natural Science Foundation of China (Grant Nos. 41704088 and 11804284), the Open Foundation of Hypervelocity Impact Research Center of CARDC (Grant No. 20200202). The thermoelastic data used are listed in the Supporting Information (SI) and references.

In the last decades, global seismic observations have identified increasingly complex anisotropy of the Earth’s inner core. Plenty of seismic studies have confirmed the anisotropy presents hemispherical variations in inner core. Here we report the effect of light elements on the anisotropy of hcp iron under inner core conditions based on ab initio molecular dynamics calculations. We found that light elements have significant effects on the density, sound velocities, and the anisotropy of hcp-Fe-X (X = C, O, Si, and S) binary alloy. For these binary alloys, the anisotropy depends on combined effects of temperature and the type of light element. Furthermore, there is a certain increase of the anisotropy strength with the increasing temperature. Alloying iron with some light elements such as C or O actually does not improve but reduces the strength of anisotropy of pure iron at high temperatures. Oppositely, light element S can significantly enhance the elastic anisotropy strength of hcp-Fe.

Key words: iron, elastic constants, anisotropy, inner core

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The anisotropy of hcp iron under inner core conditions: the effect of light elements

Wei Zhang, Mei Tang, ZhenWei Niu