Effect of light elements (S, Si, C, O) on liquid iron alloys structural properties under high pressure studied by XRD, XANES and molecular dynamics

Abstract:

The liquid core of the Earth extends between 2900 km and 5150 km depth accounting for 18% of the total planetary volume. Although mostly composed of iron, it contains impurities that lower its density and melting point with respect to pure Fe. Knowledge of the nature and content of the light elements (O, S, Si, C) in the core has major implications for establishing the bulk composition of the Earth and for building models of Earth’s differentiation.

We will present XRD and XANES experimental results on liquid iron alloys measured using the Laser-Heated Diamond Anvil Cell (LH-DAC) up to megabar conditions, obtained respectively on ESRF beamlines ID27 and ID24. Measurements have been performed on different samples : Fe-10 wt%O ; Fe-10wt% Si ; Fe-5wt%Ni-12wt%S ; Fe-1.5wt% C. Using this dataset, we are able to probe the electronic structure and crystallographic structures of these iron alloys from solid phases up to the liquid state. Comparison between these measurements and ab initio calculations of the local structure of these liquids, allows us to discuss how the different light elements S, Si, O and C affect the properties of liquid iron alloys.