First-principles study of intermediate-spin ferrous iron in the Earth's lower mantle

Abstract

Spin crossover of iron is of central importance in solid Earth geophysics. It impacts all physical properties of minerals that altogether constitute $\sim 95$ vol\% of the Earth's lower mantle: ferropericlase [(Mg,Fe)O] and Fe-bearing magnesium silicate (MgSiO${}_3$) perovskite. Despite great strides made in the past decade, the existence of intermediate-spin (IS) state in ferrous iron (Fe${}^{2+}$) (with total electron spin $S=1$) and its possible role in the pressure-induced spin crossover in these lower-mantle minerals still remain controversial. Using density functional theory $+$ self-consistent Hubbard $U$ (DFT$+U_{sc}$) calculations, we investigate all possible types of IS states of Fe${}^{2+}$ in (Mg,Fe)O and (Mg,Fe)SiO${}_3$ perovskite. Among the possible IS states in these minerals, the most probable IS state has an electronic configuration that significantly reduces the electron overlap and the iron nuclear quadrupole splitting (QS). These most probable IS states, however, are still energetically disfavored, and their QSs are inconsistent with Mössbauer spectra. We therefore conclude that IS Fe${}^{2+}$ is highly unlikely in the Earth's lower mantle.

References in corpus (19)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• A linear response approach to the calculation of the effective interaction parameters in the LDA+U method
• Density functional theory in transition-metal chemistry: a self-consistent Hubbard U approach
• Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors
• Extended DFT+U+V method with on-site and inter-site electronic interactions
• Anomalous compressibility of ferropericlase throughout the iron spin crossover
• Strain-Induced Spin States in Atomically Ordered Cobaltites
• Spin-state crossover and hyperfine interactions of ferric iron in MgSiO${}_3$ perovskite
• First principles study of electronic and structural properties of CuO
• Soft x-ray magnetic circular dichroism of LaCoO${}_3$, La${}_{0.7}$Ce${}_{0.3}$CoO${}_3$, and La${}_{0.7}$Sr${}_{0.3}$CoO${}_3$ films: Evidence for Co valency-dependent magnetism and magnetic anisotropy
• Structural effects on the spin-state transition in epitaxially strained LaCoO${}_3$ films
• Reversible strain effect on the magnetization of LaCoO3 films
• Mott Transition in Multi-Orbital Models for Iron Pnictides
• Ferromagnetic insulating state in tensile-strained LaCoO${}_3$ thin films
• Suppression of the ferromagnetic state in LaCoO3 films by rhombohedral distortion
• Anomalous optical phonons in FeTe pnictides: spin state, magnetic order, and lattice anharmonicity
• Suppression of spin-state transition in epitaxially strained LaCoO_{3}
• Coexistence of different electronic phases in the K0.8Fe1.6Se2 superconductor: a bulk-sensitive hard x-rays spectroscopy study
• Spin states of iron impurities in magnesium oxide under pressure: A possible intermediate state

Cited by in corpus (14)

• Thermoelasticity of Fe2+-bearing bridgmanite
• Spin crossover in (Mg,Fe${}^{3+}$)(Si,Fe${}^{3+}$)O${}_3$ bridgmanite: effects of disorder, iron concentration, and temperature
• First-principles study of crystal and electronic structure of rare-earth cobaltites
• LDA+Usc calculations of phase relations in FeO
• Influence of the iron spin crossover in ferropericlase on the lower mantle geotherm
• Phonon dispersions throughout the iron spin crossover in ferropericlase
• Anomalous thermal properties and spin crossover of ferromagnesite (Mg,Fe)CO3
• Phase transitions and spin-state of iron in FeO at the conditions of Earth's deep interior
• Intermediate spin state and the B1-B2 transition in ferropericlase at tera-Pascal pressures
• Structural transition and re-emergence of iron's total electron spin in (Mg,Fe)O at ultrahigh pressure
• Evidence for a pressure-induced spin transition in olivine-type LiFePO${}_4$ triphylite
• Thermoelasticity of Fe${}^{3+}$- and Al-bearing bridgmanite
• Iron spin crossover and its influence on post-perovskite transitions in MgSiO${}_3$ and MgGeO${}_3$
• Optical signatures of low spin Fe3+: a new probe for the spin state of bridgmanite and post-perovskite