Fe-Si system: a potential major component of the Earth's core
Abstract
We investigate Silicon in the Earth's core using first-principles calculations. Specifically we look at the phase diagram of the Fe-Si system, the solubility limits of Si into hcp Fe, and the effect of Si on the thermal and electrical conductivities of iron. We consider several Fe hcp supercells and replace some of the Fe atoms with Si in different amounts and configurations. In this way we mimic the dissolution of silicon into hcp and take into account a realistic solid solution. Silicon slightly increases the specific volume of iron, but the differences levels out at high pressures. We show that the density and seismic profiles of the core can be easily matched by Fe-Si alloys with small amounts of Si. Further phonon analysis suggests that stoichiometric Fe3Si is dynamically unstable at high pressure. This results in decomposition into Si-bearing hcp Fe and Fe-bearing B2 FeSi. Then we follow the evolution of the Fe-FeSi immiscibility gap as a function of pressure. Finally we compute the electrical and thermal conductivities of Si-bearing hcp iron at inner core conditions. We obtain that a relatively small amount of Si decreases the conductivity of iron. Based on these considerations we conclude that Si can be the preferred light element of the Earth's core.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMMR21A2331C
- Keywords:
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- 3924 MINERAL PHYSICS High-pressure behavior;
- 3919 MINERAL PHYSICS Equations of state;
- 1015 GEOCHEMISTRY Composition of the core;
- 5139 PHYSICAL PROPERTIES OF ROCKS Transport properties