Iron-rich Fe–O compounds at Earth’s core pressures
Year: 2022
Type: article
Abstract: Oxygen and iron are the most abundant elements on Earth, and their compounds are key planet-forming components. While oxygen is pervasive in the mantle, its presence in the solid inner core is still debatable. Yet, this issue is critical to understanding the co-evolution and the geomagnetic field generation. Thus far, iron monoxide (FeO) is the only known stoichiometric compound in the Fe–FeO system, and the existence of iron-rich Fe n O compounds has long been speculated. Here, we report that iron reacts with FeO and Fe 2 O 3 at 220–260 GPa and 3000–3500 K in laser-heated diamond anvil cells. Ab initio structure searches using the adaptive genetic algorithm indicate that a series of stable stoichiometric Fe n O compounds (with n > 1) can be formed. Like ε–Fe and B8–FeO, Fe n O compounds have close-packed layered structures featuring oxygen-only single layers separated by iron-only layers. Two solid-solution models with compositions close to Fe 2 O, the most stable Fe-rich phase identified, explain the X-ray diffraction patterns of the experimental reaction products quenched to room temperature. These results suggest that Fe-rich Fe n O compounds with close-packed layered motifs might be stable under inner core conditions. Future studies of the elastic, rheological, and thermal transport properties of these more anisotropic Fe n O solids should provide new insights into the seismic features of the inner core, inner core formation process and composition, and the thermal evolution of the planet.
Source: The Innovation
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $5,000
Awards: G102163711, G107546177, G1313983767, G1549569010, GEOSOILENVIROCARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY, SOIL AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G1664757510, G1953852693, G1996433053, Collaborative Research: Thermodynamics and thermoelasticity of iron-bearing phases, High Pressure-Temperature Single-Crystal Elasticity of the Lower-Mantle Bridgmanite, G2287611682, G2520931197, G262962599, G3075337988, G3226045097, AB INITIO GEOCHEMISTRY OF HYDROUS PHASES, Collaborative Research: Thermodynamics and thermoelasticity of iron-bearing phases, XSEDE 2.0: Integrating, Enabling and Enhancing National Cyberinfrastructure with Expanding Community Involvement, Building Capacity for Safer Post-disaster Shelter: Leveraging Local Understanding and Advanced Engineering Assessments, GEO CARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G4382344593, Facility Support: GeoSoilEnviroCARS: A National Resource for Earth, Planetary, Soil and Environmental Science Research at the APS, G498139845, G513797252, G6806689448, G6918803902, G7149950122, G7275060768, G8388731330, G8476287177, 碳元素对铁合金的高压熔融的影响及其对深部碳循环的启示, G880751848, GEO CARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G993149817
OpenAlex ID: W4309333347