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

Wednesday, 17 December 2014
Guillaume Morard1, Denis Andrault2, Daniele Antonangeli1, Julien Siebert3, Francois J Guyot1, Anne-line Auzende1, Oliver T Lord4, Johann Bouchet5, Marion Harmand6, Benjamin Cochain7, Gaston Garbarino8, Innokenty Kantor8, Raffaella Torchio8, Eglantine Boulard8 and Nohamed Mezouar8, (1)IMPMC Institut de Minéralogie et de Physique des Milieux Condensés, Paris Cedex 05, France, (2)Laboratoire Magmas et Volcans, Clermont-Ferrand Cedex, France, (3)Institut de Physique du Globe de Paris, Paris, France, (4)University of Bristol, Bristol, BS8, United Kingdom, (5)CEA Commissariat à l'Energie Atomique DAM, Arpajon Cedex, France, (6)Ecole Polytechnique, Palaiseau Cedex, France, (7)University Pierre and Marie Curie Paris VI, Paris, France, (8)ESRF European Synchrotron Radiation Facility, Grenoble, France
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.