Effect of light elements on the sound velocities in solid iron: Implications for the composition of Earth's core

Badro, James; Fiquet, G.; Guyot, F.; Gregoryanz, Eugene; Occelli, F.; Antonangeli, Daniele; d’Astuto, Matteo

doi:10.1016/j.epsl.2006.11.025

Cited by 229 publications

(152 citation statements)

References 38 publications

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“…VP in a highly textured hcp-Fe sample displayed a difference of 4-5% between the two velocities at 50° and 90° from the c-axis, which is of the same order of the seismic anisotropy in Earth's inner core [539,540]. The effects of light elements on the sound velocities in iron were studied by measuring VP in FeO, FeSi, FeS, Fe0.89Ni0.04Si0.07, and FeS2 at HP [286,287,541,542]. HERIXS measurements have been recently extended to high temperatures [291][292][293].…”

Section: Sound Velocitiesmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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Pressure profoundly alters all states of matter. The symbiotic development of ultrahighpressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

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Section: Sound Velocitiesmentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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“…The prime light-element candidates for the core, taking into account cosmochemical and petrological constraints, are silicon, sulfur, carbon, oxygen, and hydrogen (6). Models for core composition allow in principio a mixture of several light elements, and many arguments have been put forward over the years for and against each of the elements (2,7,8).…”

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confidence: 99%

A seismologically consistent compositional model of Earth’s core

Badro

Côté

Brodholt

2014

Proc. Natl. Acad. Sci. U.S.A.

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289

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Earth's core is less dense than iron, and therefore it must contain "light elements," such as S, Si, O, or C. We use ab initio molecular dynamics to calculate the density and bulk sound velocity in liquid metal alloys at the pressure and temperature conditions of Earth's outer core. We compare the velocity and density for any composition in the (Fe-Ni, C, O, Si, S) system to radial seismological models and find a range of compositional models that fit the seismological data. We find no oxygen-free composition that fits the seismological data, and therefore our results indicate that oxygen is always required in the outer core. An oxygen-rich core is a strong indication of high-pressure and high-temperature conditions of core differentiation in a deep magma ocean with an FeO concentration (oxygen fugacity) higher than that of the present-day mantle.mineral physics | first principles | geophysics

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“…By using the ab-initio partition coefficient of D Si (liquid iron/solid iron) = 1.26 [Alfè et al, 2002] the outer core then contains 2.9 wt% Si [Badro et al, 2007]. This gives a whole core (inner + outer) Si content of 2.9 wt% by using the mass ratio of the inner and the outer core [Stacey, 1992].…”

Section: Resultsmentioning

confidence: 99%

“…[17] Badro et al [2007], using both density and sound velocity, constrain that Earth's inner core contains 2.3 wt% Si. By using the ab-initio partition coefficient of D Si (liquid iron/solid iron) = 1.26 [Alfè et al, 2002] the outer core then contains 2.9 wt% Si [Badro et al, 2007].…”

Section: Resultsmentioning

confidence: 99%

“…[18] Badro et al [2007] use the experiment of Takafuji et al [2005] and the ab-initio partition coefficient of Alfè et al [2002] to constrain further the O content of the outer core. The constraint is not as strong as that for Si since the O content may not be determined by the equilibrium between liquid iron and perovskite at 97 GPa and that the error in the estimated O content of the inner core may have a large influence on the inferred O content of the outer core due to the large value of the O partition coefficient (D O (liquid iron/solid iron) of Alfè et al [2002] is 43 if weight percent is used as the unit of concentration).…”

Section: Resultsmentioning

confidence: 99%

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Partitioning of Si and O between liquid iron and silicate melt: A two‐phase ab‐initio molecular dynamics study

Zhang

Guo

2009

Geophysical Research Letters

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The magma ocean process in the early history of the Earth has a great influence on the light element identities and contents of the core which subsequently affect the energy of the geodynamo provided by the compositional convection and the inner core growth through their effect on the phase diagram of iron alloy. In the present work, a two‐phase ab‐initio molecular dynamics method is established to study the solubility of silicon and oxygen in liquid iron in equilibrium with silicate melt. The ab‐initio results are found to be in close agreement with experimental data. At the base of a deep magma ocean (39 GPa and 3116 K), liquid iron contains 2.7 wt% silicon and 0.5 wt% oxygen at the current bulk Earth composition. The oxygen content is low compared with its current estimate in the core, indicating a deeper magma ocean may need to be invoked.

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Effect of light elements on the sound velocities in solid iron: Implications for the composition of Earth's core

Cited by 229 publications

References 38 publications

High-pressure studies with x-rays using diamond anvil cells

High-pressure studies with x-rays using diamond anvil cells

A seismologically consistent compositional model of Earth’s core

Partitioning of Si and O between liquid iron and silicate melt: A two‐phase ab‐initio molecular dynamics study

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