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

Zhang, Yigang; Guo, Guang-Jun

doi:10.1029/2009gl039751

Cited by 12 publications

(8 citation statements)

References 45 publications

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“…Properties of melts in the lower mantle are critical to understanding mantle chemical evolution, and theoretical and experimental studies have addressed issues of melt density and iron fractionation and Si and O partitioning between liquids and perovskite and ferropericlase in the deep mantle (e.g., de Koker and Stixrude, 2009;de Koker et al, 2013;Fiquet et al, 2010;Frost et al, 2004;Liebske and Frost, 2012;Mosenfelder et al, 2007;Seagle et al, 2008;Stixrude et al, 2009;Terasaki et al, 2007;Zhang and Fei, 2008;Zhang and Guo, 2009).…”

Section: Mineralogical Structurementioning

confidence: 99%

Deep Earth Structure: Lower Mantle and D″

Lay

2015

Treatise on Geophysics

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Section: Mineralogical Structurementioning

confidence: 99%

Deep Earth Structure: Lower Mantle and D″

Lay

2015

Treatise on Geophysics

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“…16) and is described only briefly here. Calculations are performed by using the ab-initio total-energy and molecular-dynamics program VASP (35).…”

Section: Methodsmentioning

confidence: 99%

“…In the present study, we use the two-phase first-principles molecular dynamics (FPMD) method (16) to determine the partition coefficient of C and a few other light elements between liquid iron and silicate melt. This partition coefficient can then be combined with the composition of the bulk Earth or the primitive mantle (i.e., bulk silicate Earth) to infer the C content of the Earth's core.…”

mentioning

confidence: 99%

Carbon and other light element contents in the Earth’s core based on first-principles molecular dynamics

Zhang

Yin

2012

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

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Carbon (C) is one of the candidate light elements proposed to account for the density deficit of the Earth's core. In addition, C significantly affects siderophile and chalcophile element partitioning between metal and silicate and thus the distribution of these elements in the Earth's core and mantle. Derivation of the accretion and core-mantle segregation history of the Earth requires, therefore, an accurate knowledge of the C abundance in the Earth's core. Previous estimates of the C content of the core differ by a factor of ∼20 due to differences in assumptions and methods, and because the metal-silicate partition coefficient of C was previously unknown. Here we use two-phase first-principles molecular dynamics to derive this partition coefficient of C between liquid iron and silicate melt. We calculate a value of 9 ± 3 at 3,200 K and 40 GPa. Using this partition coefficient and the most recent estimates of bulk Earth or mantle C contents, we infer that the Earth's core contains 0.1-0.7 wt% of C. Carbon thus plays a moderate role in the density deficit of the core and in the distribution of siderophile and chalcophile elements during core-mantle segregation processes. The partition coefficients of nitrogen (N), hydrogen, helium, phosphorus, magnesium, oxygen, and silicon are also inferred and found to be in close agreement with experiments and other geochemical constraints. Contents of these elements in the core derived from applying these partition coefficients match those derived by using the cosmochemical volatility curve and geochemical mass balance arguments. N is an exception, indicating its retention in a mantle phase instead of in the core.

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“…The ab initio calculations of Alfè et al ., [] indicate that O partitions strongly from the solid inner core into the liquid outer core, and, unlike Si, can explain observed density differences and seismic data. On the other hand, a two‐phase ab initio study of metal and silicate liquids has demonstrated that the partitioning of O into the Fe‐metal liquid is very limited, at least at 3100 K [ Zhang and Guo , ]. A high‐pressure experimental study using inelastic X‐ray scattering supports the presence of oxygen in the core [ Badro et al ., ], whereas an X‐ray diffraction study [ Sata et al ., ] precludes it.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous partitioning of silicon and oxygen into the Earth's core during early Earth differentiation

Tsuno

Frost

Rubie

2013

Geophysical Research Letters

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[1] Silicon and oxygen are potential light elements in the Earth's core and may be involved in metal-silicate reactions at the present day core-mantle boundary. We have performed multianvil experiments at 25 GPa and 2770-3080 K to understand the simultaneous partitioning of these elements between liquid iron-rich metal and silicate melt. The presence of O in liquid Fe at high temperatures influences the partitioning of Si, causing more Si to partition into the metal than would be expected based on lower temperature measurements. Although Si and O are mutually exclusive in Fe metal at <3000 K, the level at which both element concentrations are similar in the liquid metal rises above 1 wt % at >3000 K. We have developed a thermodynamic model based on these experiments that accounts for the interaction between O and Si in the liquid metal. Comparison between this model and the previous results of diamond-anvil cell experiments up to 71 GPa indicates very little pressure dependence but a strong temperature dependence for O and Si partitioning. Our model predicts that subequal concentrations of Si and O, sufficient to explain the outer core density deficit, would have partitioned into core-forming metal if equilibration occurred between the metal and a magma ocean with a bulk silicate Earth composition at an average depth of~1200 km (~50 GPa and~3300 K). An O-and Sienriched buoyant layer may have developed at the top of the outer core as a result of subsequent equilibration with the overlying mantle. Citation: Tsuno K., D J. Frost, and D. C.Rubie, (2013), Simultaneous partitioning of silicon and oxygen into the Earth's core during early Earth differentiation, Geophys. Res. Lett., 40,[66][67][68][69][70][71]

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

Cited by 12 publications

References 45 publications

Deep Earth Structure: Lower Mantle and D″

Deep Earth Structure: Lower Mantle and D″

Carbon and other light element contents in the Earth’s core based on first-principles molecular dynamics

Simultaneous partitioning of silicon and oxygen into the Earth's core during early Earth differentiation

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