Sound velocities and density measurements of solid hcp-Fe and hcp-Fe–Si (9 wt.%) alloy at high pressure: Constraints on the Si abundance in the Earth's inner core

Antonangeli, Daniele; Morard, Guillaume; Paolasini, L.; Garbarino, Gastón; Murphy, C. A.; Edmund, Eric; Decremps, F.; Fiquet, G.; Bosak, Alexeï; Mézouar, M.; Fei, Yingwei

doi:10.1016/j.epsl.2017.11.043

Cited by 35 publications

(61 citation statements)

References 45 publications

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“…Similar to the trends in v D , our reported v S for hcp-Fe agrees well with Mao et al (2001), Lin et al (2005), Mao et al (2008), Liu et al (2016), and it is only the 136 GPa data point of Gleason et al (2013) that appears to deviate significantly from these trends. The IXS studies by Antonangeli et al (2018) and Ohtani et al (2013) report v S curves based on their determined v P and existing equations of state (Dewaele et al, 2006;Sakai et al, 2014). The v S of Antonangeli et al (2018) and Ohtani et al (2013) trend respectively ∼5% and ∼11% above our reported v S for hcp-Fe, which is a significant deviation.…”

Section: Ironcontrasting

confidence: 47%

“…A variety of studies have investigated the sound velocities of iron-silicon alloys at 300 K (Lin et al, 2003;Badro et al, 2007;Mao et al, 2012;Ono, 2013;Liu et al, 2014;Antonangeli et al, 2018;Sakairi et al, 2018). Silicon is found to increase the compressional velocity of hcp-Fe, but the effect of silicon on hcp-Fe's shear velocity is debated.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…The sound velocities of hcp-iron have been extensively studied through shockwave experiments (Jeanloz, 1979;Brown and Mcqueen, 1986;Nguyen and Holmes, 2004), 300 K static compression experiments (Lübbers et al, 2000;Mao et al, 2001;Giefers et al, 2002;Antonangeli et al, 2004;Lin et al, 2005;Mao et al, 2008Mao et al, , 2012Murphy et al, 2013;Gleason et al, 2013;Ohtani et al, 2013;Decremps et al, 2014;Liu et al, 2014Liu et al, , 2016Antonangeli et al, 2018), high temperature static compression experiments (Lin et al, 2005;Sakamaki et al, 2016;Mori et al, 2017), and ab initio studies (Laio et al, 2000;Mao et al, 2001;Steinle-Neumann et al, 2001;Vočadlo et al, 2009;Martorell et al, 2013a;Niu et al, 2015). Similarly, numerous experimental and ab initio studies have investigated hcp-iron's isothermal equation of state (e.g.…”

Section: Introductionmentioning

confidence: 99%

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High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

Morrison

Jackson

Sturhahn

et al. 2019

Physics of the Earth and Planetary Interiors

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The Earth's iron-dominant core is known to contain nickel from cosmochemical analysis and some amount of light elements from geophysical constraints on density and seismic wave velocities. Although there have been several studies to constrain thermoelastic properties of iron-alloys, there has been no systematic study on the effects of nickel and light elements on properties of iron using the same experimental methods and data analysis approach. We conducted nuclear resonant inelastic x-ray scattering and x-ray diffraction experiments on body-centered cubic and hexagonal close-packed (hcp) Fe 0.91 Ni 0.09 and Fe 0.8 Ni 0.1 Si 0.1 up to 104 GPa and 86 GPa, respectively, and compare to similar measurements conducted on hcp-Fe up to 171 GPa. Specifically, we determine the Debye sound velocity from the low-energy transfer region of the (partial) phonon density of states (DOS) using the equation of state determined for each material and a new approach which utilizes information criteria and probability distributions. Nickel decreases the shear velocity of iron, while 10 at% Si has little to no effect on the shear velocity of Fe 0.91 Ni 0.09. We observe that the shape of the phonon DOS of these alloys remains similar with increasing pressure. In the measured compression range, we therefore apply a generalized scaling law to describe the volume dependence of the phonon DOS and find that the vibrational Grüneisen parameters of hcp-Fe 0.91 Ni 0.09 are nearly indistinguishable from those hcp-Fe and those for Fe 0.8 Ni 0.1 Si 0.1 trend lower. From the vibrational free energy, we constrain the harmonic vibrational component of thermal pressure, which shows a significant positive deviation from theoretical calculations of hcp-Fe at pressures and temperatures of Earth's core. Collectively, our results demonstrate that the effects of nickel should be considered when modeling iron-rich planetary cores.

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Section: Ironcontrasting

confidence: 47%

Section: Accepted Manuscriptmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

Morrison

Jackson

Sturhahn

et al. 2019

Physics of the Earth and Planetary Interiors

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“…To do so, we apply a linear mixing model. Badro et al (2007) propose linear mixing should hold for hcp-iron alloyed with low concentrations of light elements, and this approach has been applied to various solid iron alloys (e.g., Antonangeli et al, 2010Antonangeli et al, , 2018Badro et al, 2007;Fiquet et al, 2009;Ohtani, 2013). Linear mixing is therefore a reasonable approximation for a mixing of hcp-Fe, hcp-Fe 0.91 Ni 0.09 , and hcp-Fe 0.8 Ni 0.1 Si 0.1 .…”

Section: Seismic and Experimental Constraints On Core Composition 53mentioning

confidence: 99%

Equations of State and Anisotropy of Fe‐Ni‐Si Alloys

et al. 2018

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We present powder X‐ray diffraction data on body centered cubic (bcc)‐ and hexagonal close packed (hcp)‐structured Fe0.91Ni0.09 and Fe0.8Ni0.1Si0.1 at 300 K up to 167 and 175 GPa, respectively. The alloys were loaded with tungsten powder as a pressure calibrant and helium as a pressure transmitting medium into diamond anvil cells, and their equations of state and axial ratios were measured with high statistical quality. These equations of state are combined with thermal parameters from previous reports to improve the extrapolation of the density, adiabatic bulk modulus, and bulk sound speed to the pressures and temperatures of Earth's inner core. We propagate uncertainties and place constraints on the composition of Earth's inner core by combining these results with available data on light‐element alloys of iron and seismic observations. For example, the addition of 4.3 to 5.3 wt% silicon to Fe0.95Ni0.05 alone can explain geophysical observations of the inner core boundary, as can up to 7.5 wt% sulfur with negligible amounts of silicon and oxygen. Our findings favor an inner core with less than ∼2 wt% oxygen and less than 1 wt% carbon, although uncertainties in electronic and anharmonic contributions to the equations of state may shift these values. The compositional space widens toward the center of the Earth, considering inner core seismic gradients. We demonstrate that hcp‐Fe0.91Ni0.09 and hcp‐Fe0.8Ni0.1Si0.1 have measurably greater c/a axial ratios than those of hcp‐Fe over the measured pressure range. We further investigate the relationship between the axial ratios, their pressure derivatives, and elastic anisotropy of hcp‐structured materials.

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“…Consequently, the interpretations of the changes in the linear physicomechanical properties of the material due to deformation (pressure increase) are incorrect and unacceptable. Although in countless published articles including magazines of Category 1 (Antonangeli et al, 2018;Bin & Xiaojing, 2018;Channing et al, 2015;Chatterjee et al, 2017;Fischer et al, 2018;Guliyev, Akbarov, et al, 2018;Litasov & Shatskiy, 2016;Prescher et al, 2015) and in generalized monographs and textbooks (Anderson,…”

Section: The "Key" To Geomechanical Analysismentioning

confidence: 99%

Once Again on Preliminary Reference Earth Model

Guliyev

Javanshir

2020

Earth and Space Science

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We studied the isotropic ball using data of Preliminary Reference Earth Model (PREM). It is shown that such a ball should be either destructed or gone into a more stable equilibrium state with uneven distributed deformation under thermobaric condition of the inner core. Body elastic waves with real velocities cannot propagate in it. This manuscript is devoted to study the situation from the standpoint of nonlinear geomechanics. A number of necessary principles of Mechanics of Deformable Solid Body (MDSB) is given at the beginning of the analysis. A brief review of the published latest experimental work is performed. It is established that proper attention to the role of the MDSB principles in micro‐scale (nano) experiments of the physical level has not been given. Deformation properties of solid bodies are emphasized in microscale and macroscale. Application of linear acoustoelasticity and extrapolation of Birch's linear law of the inner core and use of an idea on variability of elasticity moduli with the increase of pressure and temperature have contributed to obtained pseudo data for the geological medium of the Earth's core instead of linear data on the physicomechanical properties. It is proposed that parallel to elimination of the indicated disadvantages, collection, processing and interpretation should be performed using nonclassically linearized approach. This set of necessary actions is offered as the “key” of geomechanical analysis. The proper application will allow conducting similar analysis concerning other solid‐state structures of the Earth.

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Sound velocities and density measurements of solid hcp-Fe and hcp-Fe–Si (9 wt.%) alloy at high pressure: Constraints on the Si abundance in the Earth's inner core

Cited by 35 publications

References 45 publications

High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

High pressure thermoelasticity and sound velocities of Fe-Ni-Si alloys

Equations of State and Anisotropy of Fe‐Ni‐Si Alloys

Once Again on Preliminary Reference Earth Model

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