Oxygen in the Earth's core: a first principles study

Abstract

First principles electronic structure calculations based on density functional theory have been used to study the thermodynamic, structural and transport properties of solid solutions and liquid alloys of iron and oxygen at Earth's core conditions. Aims of the work are to determine the oxygen concentration needed to account for the inferred density in the outer core, to probe the stability of the liquid against phase separation, to interpret the bonding in the liquid, and to find out whether the viscosity differs significantly from that of pure liquid iron at the same conditions. It is shown that the required concentration of oxygen is in the region 25-30 mol percent, and evidence is presented for phase stability at these conditions. The Fe-O bonding is partly ionic, but with a strong covalent component. The viscosity is lower than that of pure liquid iron at Earth's core conditions. It is shown that earlier first-principles calculations indicating very large enthalpies of formation of solid solutions may need reinterpretation, since the assumed crystal structures are not the most stable at the oxygen concentration of interest.

21 pages, 12 figures

References in corpus (4)

• The first principles calculation of transport coefficients
• First principles simulations of liquid Fe-S under Earth's core conditions
• The Structure, Dynamics and Electronic Structure of Liquid Ag-Se Alloys Investigated by Ab Initio Simulation
• Composition Dependence of the Structure and Electronic Properties of Liquid Ga-Se Alloys Studied by Ab Initio Molecular Dynamics Simulation

Cited by in corpus (6)

• Structure and Dynamics of Liquid Iron under Earth's Core Conditions
• Transport properties for liquid silicon-oxygen-iron mixtures at Earth's core conditions
• Ab-initio chemical potentials of solid and liquid solutions and the chemistry of the Earth's core
• A deep machine learning potential for atomistic simulation of Fe-Si-O systems under Earth's outer core conditions
• Thermodynamic stability of Fe/O solid solution at inner-core conditions
• Iron-rich Fe-O compounds with closest-packed layers at core pressures