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地球与行星物理

ISSN  2096-3955

CN  10-1502/P

Citation: Zhang, W., Tang, M., and Niu, Z. W. (2022). The anisotropy of hexagonal close-packed iron under inner core conditions: the effect of light elements. Earth Planet. Phys., 6(4), 399–423. http://doi.org/10.26464/epp2022035

2022, 6(4): 399-423. doi: 10.26464/epp2022035

SOLID EARTH: COMPUTATIONAL GEOPHYSICS

The anisotropy of hexagonal close-packed iron under inner core conditions: the effect of light elements

1. 

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

2. 

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

3. 

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

Corresponding author: ZhenWei Niu, z.w.niu@foxmail.com

Received Date: 2022-02-21
Web Publishing Date: 2022-06-02

In recent decades, global seismic observations have identified increasingly complex anisotropy of the Earth’s inner core. Numerous seismic studies have confirmed hemispherical variations in the inner core’s anisotropy. Here, based on ab initio molecular dynamics calculations, we report how the anisotropy of hexagonal close-packed (hcp)-iron, under inner core conditions, could be altered when alloyed with light elements. We find that light elements in binary allows with iron — hcp-Fe-X (X = C, O, Si, and S) — could have significant effects on density, sound velocities, and anisotropy, compared with the behavior of pure hcp-iron; the anisotropy of these binary alloys depends on combined effects of temperature and the particular alloying light element. Furthermore, the change in anisotropy strength with increasing temperature can be charted for each alloy. Alloying pure iron with some light elements such as C or O actually does not increase but decreases core anisotropy at high temperatures. But the 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 hexagonal close-packed iron under inner core conditions: the effect of light elements

Wei Zhang, Mei Tang, ZhenWei Niu