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Cobden L, Zhuang J, Lei W, Wentzcovitch R, Trampert J, Tromp J. Full-waveform tomography reveals iron spin crossover in Earth's lower mantle. Nat Commun 2024; 15:1961. [PMID: 38438365 PMCID: PMC10912123 DOI: 10.1038/s41467-024-46040-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Accepted: 02/12/2024] [Indexed: 03/06/2024] Open
Abstract
Three-dimensional models of Earth's seismic structure can be used to identify temperature-dependent phenomena, including mineralogical phase and spin transformations, that are obscured in 1-D spherical averages. Full-waveform tomography maps seismic wave-speeds inside the Earth in three dimensions, at a higher resolution than classical methods. By providing absolute wave speeds (rather than perturbations) and simultaneously constraining bulk and shear wave speeds over the same frequency range, it becomes feasible to distinguish variations in temperature from changes in composition or spin state. We present a quantitative joint interpretation of bulk and shear wave speeds in the lower mantle, using a recently published full-waveform tomography model. At all depths the diversity of wave speeds cannot be explained by an isochemical mantle. Between 1000 and 2500 km depth, hypothetical mantle models containing an electronic spin crossover in ferropericlase provide a significantly better fit to the wave-speed distributions, as well as more realistic temperatures and silica contents, than models without a spin crossover. Below 2500 km, wave speed distributions are explained by an enrichment in silica towards the core-mantle boundary. This silica enrichment may represent the fractionated remains of an ancient basal magma ocean.
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Affiliation(s)
- Laura Cobden
- Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, Utrecht, The Netherlands.
| | - Jingyi Zhuang
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, 10027, USA
| | - Wenjie Lei
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, 10027, USA
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
- Google Inc., Mountain View, CA, USA
| | - Renata Wentzcovitch
- Department of Earth and Environmental Sciences, Columbia University, New York, NY, 10027, USA.
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, 10027, USA.
- Lamont Doherty Earth Observatory, Palisades, NY, 10964, USA.
- Data Science Institute, Columbia University, New York, NY, 10027, USA.
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY, 10010, USA.
| | - Jeannot Trampert
- Department of Earth Sciences, Utrecht University, 3584 CB Utrecht, Utrecht, The Netherlands
| | - Jeroen Tromp
- Department of Geosciences, Princeton University, Princeton, NJ, 08544, USA
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2
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He ZD, Tesch R, Eslamibidgoli MJ, Eikerling MH, Kowalski PM. Low-spin state of Fe in Fe-doped NiOOH electrocatalysts. Nat Commun 2023; 14:3498. [PMID: 37311755 DOI: 10.1038/s41467-023-38978-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 05/23/2023] [Indexed: 06/15/2023] Open
Abstract
Doping with Fe boosts the electrocatalytic performance of NiOOH for the oxygen evolution reaction (OER). To understand this effect, we have employed state-of-the-art electronic structure calculations and thermodynamic modeling. Our study reveals that at low concentrations Fe exists in a low-spin state. Only this spin state explains the large solubility limit of Fe and similarity of Fe-O and Ni-O bond lengths measured in the Fe-doped NiOOH phase. The low-spin state renders the surface Fe sites highly active for the OER. The low-to-high spin transition at the Fe concentration of ~ 25% is consistent with the experimentally determined solubility limit of Fe in NiOOH. The thermodynamic overpotentials computed for doped and pure materials, η = 0.42 V and 0.77 V, agree well with the measured values. Our results indicate a key role of the low-spin state of Fe for the OER activity of Fe-doped NiOOH electrocatalysts.
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Affiliation(s)
- Zheng-Da He
- Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425, Jülich, Germany
- JARA Energy & Center for Simulation and Data Science (CSD), 52425, Jülich, Germany
| | - Rebekka Tesch
- Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425, Jülich, Germany
- JARA Energy & Center for Simulation and Data Science (CSD), 52425, Jülich, Germany
- Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Engineering, RWTH Aachen University, 52062, Aachen, Germany
| | - Mohammad J Eslamibidgoli
- Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425, Jülich, Germany
- JARA Energy & Center for Simulation and Data Science (CSD), 52425, Jülich, Germany
| | - Michael H Eikerling
- Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425, Jülich, Germany
- JARA Energy & Center for Simulation and Data Science (CSD), 52425, Jülich, Germany
- Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Engineering, RWTH Aachen University, 52062, Aachen, Germany
| | - Piotr M Kowalski
- Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, 52425, Jülich, Germany.
- JARA Energy & Center for Simulation and Data Science (CSD), 52425, Jülich, Germany.
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Hsu H, Umemoto K. Structural transition and re-emergence of iron's total electron spin in (Mg,Fe)O at ultrahigh pressure. Nat Commun 2022; 13:2780. [PMID: 35589702 PMCID: PMC9120148 DOI: 10.1038/s41467-022-30100-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 04/06/2022] [Indexed: 11/14/2022] Open
Abstract
Fe-bearing MgO [(Mg1−xFex)O] is considered a major constituent of terrestrial exoplanets. Crystallizing in the B1 structure in the Earth’s lower mantle, (Mg1−xFex)O undergoes a high-spin (S = 2) to low-spin (S = 0) transition at ∼45 GPa, accompanied by anomalous changes of this mineral’s physical properties, while the intermediate-spin (S = 1) state has not been observed. In this work, we investigate (Mg1−xFex)O (x ≤ 0.25) up to 1.8 TPa via first-principles calculations. Our calculations indicate that (Mg1−xFex)O undergoes a simultaneous structural and spin transition at ∼0.6 TPa, from the B1 phase low-spin state to the B2 phase intermediate-spin state, with Fe’s total electron spin S re-emerging from 0 to 1 at ultrahigh pressure. Upon further compression, an intermediate-to-low spin transition occurs in the B2 phase. Depending on the Fe concentration (x), metal–insulator transition and rhombohedral distortions can also occur in the B2 phase. These results suggest that Fe and spin transition may affect planetary interiors over a vast pressure range. Iron spin transition occurs at ultrahigh pressure. The total electron spin increases from 0 to 1 as the structural transition of (Mg,Fe)O occurs (~0.6 TPa) and drops back to 0 at higher pressure. Its effects on exoplanet interiors are anticipated.
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Affiliation(s)
- Han Hsu
- Department of Physics, National Central University, Taoyuan City, 320317, Taiwan.
| | - Koichiro Umemoto
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan
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Shephard GE, Houser C, Hernlund JW, Valencia-Cardona JJ, Trønnes RG, Wentzcovitch RM. Seismological expression of the iron spin crossover in ferropericlase in the Earth's lower mantle. Nat Commun 2021; 12:5905. [PMID: 34625555 PMCID: PMC8501025 DOI: 10.1038/s41467-021-26115-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 09/17/2021] [Indexed: 11/19/2022] Open
Abstract
The two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the ~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below ~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover. This study identifies the predicted seismic expression of the high-to-low iron spin crossover in the deep Earth mineral ferropericlase. A depth-dependent signal is detected in the fastest and slowest regions, related to lateral temperature variations, of several global seismic tomography models.
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Affiliation(s)
- Grace E Shephard
- Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, Oslo, Norway.
| | - Christine Houser
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | - John W Hernlund
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, Japan
| | | | - Reidar G Trønnes
- Centre for Earth Evolution and Dynamics (CEED), Department of Geosciences, University of Oslo, Oslo, Norway.,Natural History Museum, University of Oslo, Oslo, Norway
| | - Renata M Wentzcovitch
- Department of Earth and Environmental Sciences, Columbia University, New York City, NY, USA. .,Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA. .,Department of Applied Physics and Applied Mathematics, Columbia University, New York City, NY, USA.
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Hu Q, Liu J, Chen J, Yan B, Meng Y, Prakapenka VB, Mao WL, Mao HK. Mineralogy of the deep lower mantle in the presence of H 2O. Natl Sci Rev 2021; 8:nwaa098. [PMID: 34691606 PMCID: PMC8288427 DOI: 10.1093/nsr/nwaa098] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/08/2020] [Accepted: 05/11/2020] [Indexed: 11/12/2022] Open
Abstract
Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800-2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H2O to form a previously unknown (Mg, Fe)O2H x (x ≤ 1) phase. The (Mg, Fe)O2H x has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg0.6Fe0.4)O or beyond 2300 km for (Mg0.7Fe0.3)O. The (Mg, Fe)O2H x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg2+, Fe3+ and H+). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.
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Affiliation(s)
- Qingyang Hu
- Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100094, China
| | - Jin Liu
- Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100094, China
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Jiuhua Chen
- Center for Study of Matter under Extreme Conditions, Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33199, USA
| | - Bingmin Yan
- Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100094, China
| | - Yue Meng
- High Pressure Collaborative Access Team (HPCAT), X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - Vitali B Prakapenka
- Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60437, USA
| | - Wendy L Mao
- Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA
| | - Ho-Kwang Mao
- Center for High Pressure Science and Technology Advanced Research (HPSTAR), Beijing 100094, China
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Experimental evidence for silica-enriched Earth's lower mantle with ferrous iron dominant bridgmanite. Proc Natl Acad Sci U S A 2020; 117:27899-27905. [PMID: 33093206 DOI: 10.1073/pnas.1917096117] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Determination of the chemical composition of the Earth's mantle is of prime importance to understand the evolution, dynamics, and origin of the Earth. However, there is a lack of experimental data on sound velocity of iron-bearing Bridgmanite (Brd) under relevant high-pressure conditions of the whole mantle, which prevents constraints on the mineralogical model of the lower mantle. To uncover these issues, we have conducted sound-velocity measurement of iron-bearing Brd in a diamond-anvil cell (DAC) up to 124 GPa using Brillouin scattering spectroscopy. Here we show that the sound velocities of iron-bearing Brd throughout the whole pressure range of lower mantle exhibit an apparent linear reduction with the iron content. Our data fit remarkably with the seismic structure throughout the lower mantle with Fe2+-enriched Brd, indicating that the greater part of the lower mantle could be occupied by Fe2+-enriched Brd. Our lower-mantle model shows a distinctive Si-enriched composition with Mg/Si of 1.14 relative to the upper mantle (Mg/Si = 1.25), which implies that the mantle convection has been inefficient enough to chemically homogenize the Earth's whole mantle.
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Velocity and density characteristics of subducted oceanic crust and the origin of lower-mantle heterogeneities. Nat Commun 2020; 11:64. [PMID: 31911578 PMCID: PMC6946644 DOI: 10.1038/s41467-019-13720-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Accepted: 11/08/2019] [Indexed: 11/08/2022] Open
Abstract
Seismic heterogeneities detected in the lower mantle were proposed to be related to subducted oceanic crust. However, the velocity and density of subducted oceanic crust at lower-mantle conditions remain unknown. Here, we report ab initio results for the elastic properties of calcium ferrite-type phases and determine the velocities and density of oceanic crust along different mantle geotherms. We find that the subducted oceanic crust shows a large negative shear velocity anomaly at the phase boundary between stishovite and CaCl2-type silica, which is highly consistent with the feature of mid-mantle scatterers. After this phase transition in silica, subducted oceanic crust will be visible as high-velocity heterogeneities as imaged by seismic tomography. This study suggests that the presence of subducted oceanic crust could provide good explanations for some lower-mantle seismic heterogeneities with different length scales except large low shear velocity provinces (LLSVPs).
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Abstract
The composition of ultralow velocity zones (ULVZs) remains an open question, despite advances in both seismology and experimental work. We investigate the hypothesis of iron-rich (Mg,Fe)O (magnesiowüstite) as a cause of ULVZ seismic signatures. We report new quasi-hydrostatic X-ray diffraction measurements to constrain the equation of state of (Mg0.06Fe0.94)O with fit parameters V0 = 9.860 ± 0.007 Å3, K0T = 155.3 ± 2.2 GPa, K’0T = 3.79 ± 0.11, as well as synchrotron Mössbauer spectroscopy measurements to characterize the high-pressure magnetic and spin state of magnesiowüstite. We combine these results with information from previous studies to calculate the elastic behavior at core–mantle boundary conditions of magnesiowüstite, as well as coexisting bridgmanite and calcium silicate perovskite. Forward models of aggregate elastic properties are computed, and from these, we construct an inverse model to determine the proportions of magnesiowüstite that best reproduce ULVZ observations within estimated mutual uncertainties. We find that the presence of magnesiowüstite can explain ULVZ observations exhibiting 1:2 VP:VS reduction ratios relative to the Preliminary Reference Earth Model (PREM), as well as certain 1:3 VP:VS reductions within estimated uncertainty bounds. Our work quantifies the viability of compositionally distinct ULVZs containing magnesiowüstite and contributes to developing a framework for a methodical approach to evaluating ULVZ hypotheses.
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Yang K, Wang X, Zhang J, Cheng Y, Zhang C, Zeng Z, Lin H. Effects of vacancy defects on Fe properties incorporated in MgO. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:295701. [PMID: 29873304 DOI: 10.1088/1361-648x/aacabd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Distributions of Fe in MgO containing Mg vacancy, O vacancy, and Schottky defect are investigated based on the density functional theory (DFT). Our results show that since Mg vacancy will remove electrons from MgO, Fe tends to get close to Mg vacancy but far from O vacancy. The Mg vacancy can decrease the magnetic moment of iron and change its valence state from 2+ to 3+, which leads to ~5% decrease of Fe-O bond length comparable to the effect of 30 GPa external pressure. Furthermore, iron incorporation can increase the Schottky defect concentration of MgO especially in the environment of the Earth's lower mantle, where ~20 mol% Fe-bearing MgO locates at extreme high temperature conditions.
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Affiliation(s)
- Kaishuai Yang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, People's Republic of China. University of Science and Technology of China, Hefei 230026, People's Republic of China. Beijing Computational Science Research Center, Beijing 100084, People's Republic of China
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Affiliation(s)
- Kei Hirose
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Ryosuke Sinmyo
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - John Hernlund
- Earth-Life Science Institute, Tokyo Institute of Technology, Meguro, Tokyo 152-8550, Japan
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Fu S, Yang J, Lin JF. Abnormal Elasticity of Single-Crystal Magnesiosiderite across the Spin Transition in Earth's Lower Mantle. PHYSICAL REVIEW LETTERS 2017; 118:036402. [PMID: 28157335 DOI: 10.1103/physrevlett.118.036402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Indexed: 06/06/2023]
Abstract
Brillouin light scattering and impulsive stimulated light scattering have been used to determine the full elastic constants of magnesiosiderite [(Mg_{0.35}Fe_{0.65})CO_{3}] up to 70 GPa at room temperature in a diamond-anvil cell. Drastic softening in C_{11}, C_{33}, C_{12}, and C_{13} elastic moduli associated with the compressive stress component and stiffening in C_{44} and C_{14} moduli associated with the shear stress component are observed to occur within the spin transition between ∼42.4 and ∼46.5 GPa. Negative values of C_{12} and C_{13} are also observed within the spin transition region. The Born criteria constants for the crystal remain positive within the spin transition, indicating that the mixed-spin state remains mechanically stable. Significant auxeticity can be related to the electronic spin transition-induced elastic anomalies based on the analysis of Poisson's ratio. These elastic anomalies are explained using a thermoelastic model for the rhombohedral system. Finally, we conclude that mixed-spin state ferromagnesite, which is potentially a major deep-carbon carrier, is expected to exhibit abnormal elasticity, including a negative Poisson's ratio of -0.6 and drastically reduced V_{P} by 10%, in Earth's midlower mantle.
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Affiliation(s)
- Suyu Fu
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jing Yang
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
| | - Jung-Fu Lin
- Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA
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Elasticity of Ferropericlase across the Spin Crossover in the Earth's Lower Mantle. Sci Rep 2015; 5:17188. [PMID: 26621579 PMCID: PMC4664863 DOI: 10.1038/srep17188] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 10/26/2015] [Indexed: 11/16/2022] Open
Abstract
Knowing the elasticity of ferropericlase across the spin transition can help explain seismic and mineralogical models of the lower-mantle including the origin of seismic heterogeneities in the middle to lowermost parts of the lower mantle1234. However, the effects of spin transition on full elastic constants of ferropericlase remain experimentally controversial due to technical challenges in directly measuring sound velocities under lower-mantle conditions12345. Here we have reliably measured both VP and VS of a single-crystal ferropericlase ((Mg0.92,Fe0.08)O) using complementary Brillouin Light Scattering and Impulsive Stimulated Light Scattering coupled with a diamond anvil cell up to 96 GPa. The derived elastic constants show drastically softened C11 and C12 within the spin transition at 40–60 GPa while C44 is not affected. The spin transition is associated with a significant reduction of the aggregate VP/VS via the aggregate VP softening because VS softening does not visibly occur within the transition. Based on thermoelastic modelling along an expected geotherm, the spin crossover in ferropericlase can contribute to 2% reduction in VP/VS in a pyrolite mineralogical model in mid lower-mantle. Our results imply that the middle to lowermost parts of the lower-mantle would exhibit enhanced seismic heterogeneities due to the occurrence of the mixed-spin and low-spin ferropericlase.
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