24-28 Sep 2017 Saint Malo (France)
Thermoelastic properties of hcp-Fe-Si-C-S alloys under the Earth's inner core conditions
Yunguo Li  1@  , Lidunka Vočadlo  1@  , John Brodholt  1@  
1 : Department of Earth Sciences [University College London]
Gower Street - London - WC1E 6BT -  United Kingdom

Geophysical and cosmochemical models constrain the inner core to be composed mainly of iron and few percent light elements including Si, S, C, and H. However, mineral physics results do not agree with the seismological observations of both density and sound wave velocities in the inner core (Vočadlo, 2007; Vočadlo et al., 2009; Belonoshko et al., 2007; Martorell et al., 2013). Recent studies suggest a candidate for the inner core could be hcp iron alloyed with light elements (Li. et al., 2001; Antonangeli, et al., 2010; Hirose, et al., 2013). Using ab initio molecular dynamics calculations, we have studied the structure and elastic properties of hcp-Fe alloys at 360 GPa up to the melting temperature. A ternary hcp-Fe30Si1C1 alloy was found to match both the inner-core density and sound velocities. We also found other possible ternary and quaternary candidates based on a solid solution model, where carbon is always a necessary component to be in agreement with the seismic observations. These Fe-C-X compositions provide a new understanding of the Earth's core with important geodynamic implications.

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