Thermal Properties of Liquid Iron at Conditions of Planetary Cores

Li, Qing; Xian, Jiawei; Zhang, Yigang; Sun, Tao; Vočadlo, Lidunka

doi:10.1029/2021je007015

Cited by 9 publications

(7 citation statements)

References 63 publications

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“…We estimate the pressure correction to be 16.6 GPa over the pressure regime of Mars’ core (19–37 GPa, Figure 1b). This is in line with (a) the observation that the difference between simulated and observed pressure becomes larger at lower pressures, for example, 8 GPa at Earth’s inner‐outer core boundary (330 GPa) and 10 GPa at its CMB (136 GPa) (Badro et al., 2014; Bajgain et al., 2021), and (b) a recent evaluation of a ρ ‐dependent pressure shift determined by comparing calculations to the density of hcp Fe and by benchmarking against that of liquid Fe at ambient pressure (Li et al., 2022), in the form of a sigmoid function ΔP = 17.38/(1 + exp(( ρ − 11.395) · 1.341)), which corresponds to a pressure correction of 17 ± 0.4 GPa in the density range of 6–9 g/cm 3 .…”

Section: Methodsmentioning

confidence: 99%

“…They have the advantage of being performed within a single computational framework that thereby eliminates random errors associated with combining distinct experimental determinations of individual binary‐ or ternary systems. Yet, most ab initio calculations have focused on higher pressures than those relevant for the Martian core, with studies focusing on applying their results to the cores of the Earth (Badro et al., 2014; D. Huang et al., 2019; Ichikawa & Tsuchiya, 2020; Umemoto & Hirose, 2020) and super‐Earths (Li et al., 2022; Wagle & Steinle‐Neumann, 2019). Relatively few ab initio studies have focused on smaller planetary cores, partly because of the complex spin transitions that occur in d ‐orbital electrons in liquid Fe at lower pressures (Edgington et al., 2019; Morard et al., 2022).…”

Section: Introductionmentioning

confidence: 99%

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Thermoelastic Properties of Liquid Fe‐Rich Alloys Under Martian Core Conditions

Huang

Khan

et al. 2023

Geophysical Research Letters

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Seismic measurements made as part of the InSight mission (Banerdt et al., 2020) indicate that Mars' core is large and light with radius and mean density ranging between 1,790 and 1,870 km and 5.7-6.3 g/cm 3 , respectively (Drilleau et al., 2022;Durán et al., 2022;Khan et al., 2022;Stähler et al., 2021). Relative to pure liquid Fe (Kuwayama et al., 2020), this implies a density deficit far in excess of that observed in Earth's core (Birch, 1964). Taken at face value, it requires the incorporation of substantial amounts of light elements (LEs) into the martian core during the early stages of planetary formation (e.g., Khan et al., 2022;Steenstra & van Westrenen, 2018). Previous work that relied mostly on analyses of martian meteorites and cosmochemical arguments (e.g., Lodders

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermoelastic Properties of Liquid Fe‐Rich Alloys Under Martian Core Conditions

Huang

Khan

et al. 2023

Geophysical Research Letters

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“…The resulting thermal equation of state P(ρ m , T) is in excellent agreement with experiments. 37 The self-diffusion coefficient of a liquid can be evaluated via two methods: One is from the long time slope of the mean square displacement (MSD), 38…”

Section: Methodsmentioning

confidence: 99%

Atomic transport properties of liquid iron at conditions of planetary cores

Sun

Zhang

et al. 2021

The Journal of Chemical Physics

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Atomic transport properties of liquid iron are important for understanding the core dynamics and magnetic field generation of terrestrial planets. Depending on the sizes of planets and their thermal histories, planetary cores may be subject to quite different pressures (P) and temperatures (T). However, previous studies on the topic mainly focus on the P-T range associated with the Earth's outer core; a systematic study covering conditions from small planets to massive exoplanets is lacking. Here, we calculate the self-diffusion coefficient (D) and viscosity (η) of liquid iron via ab initio molecular dynamics from 7.0 to 25 g/cm 3 and 1800 to 25 000 K. We find that D and η are intimately related and can be fitted together using a generalized free volume model. The resulting expressions are simpler than those from previous studies where D and η were treated separately. Moreover, the new expressions are in accordance with the quasi-universal atomic excess entropy (Sex) scaling law for strongly coupled liquids, with normalized diffusivity D ⋆ = 0.621 exp(0.842Sex) and viscosity η ⋆ = 0.171 exp(−0.843Sex). We determine D and η along two thermal profiles of great geophysical importance: the iron melting curve and the isentropic line anchored at the ambient melting point. The variations of D and η along these thermal profiles can be explained by the atomic excess entropy scaling law, demonstrating the dynamic invariance of the system under uniform time and space rescaling. Accordingly, scale invariance may serve as an underlying mechanism to unify planetary dynamos of different sizes.

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“…[116] K S Adiabatic bulk modulus 1306 GPa Ref. [116] C P Isobaric heat capacity 790 J kg −1 K −1 Ref. [116] r IC Inner-core radius 1221 km Ref.…”

Section: Fig A1 (Color Online)mentioning

confidence: 99%

“…[116] C P Isobaric heat capacity 790 J kg −1 K −1 Ref. [116] r IC Inner-core radius 1221 km Ref. [117] r OC Outer-core radius 3480 km Ref.…”

Section: Fig A1 (Color Online)mentioning

confidence: 99%

Theoretical predictions of melting behaviors of hcp iron up to 4000 GPa

Cuong,

Hoc,

Trung

et al. 2022

Preprint

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The high-pressure melting diagram of iron is a vital ingredient for the geodynamic modeling of planetary interiors. Nonetheless, available data for molten iron show an alarming discrepancy.Herein, we propose an efficient one-phase approach to capture the solid-liquid transition of iron under extreme conditions. Our basic idea is to extend the statistical moment method to determine the density of iron in the TPa region. On that basis, we adapt the work-heat equivalence principle to appropriately link equation-of-state parameters with melting properties. This strategy allows explaining cutting-edge experimental and ab initio results without massive computational workloads. Our theoretical calculations would be helpful to constrain the chemical composition, internal dynamics, and thermal evolution of the Earth and super-Earths.

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Thermal Properties of Liquid Iron at Conditions of Planetary Cores

Cited by 9 publications

References 63 publications

Thermoelastic Properties of Liquid Fe‐Rich Alloys Under Martian Core Conditions

Thermoelastic Properties of Liquid Fe‐Rich Alloys Under Martian Core Conditions

Atomic transport properties of liquid iron at conditions of planetary cores

Theoretical predictions of melting behaviors of hcp iron up to 4000 GPa

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