Surface structure and water adsorption on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>: Spin-density functional theory and on-site Coulomb interactions

Grillo, Maria Elena; Finnis, Michael W.; Ranke, Wolfgang

doi:10.1103/physrevb.77.075407

Cited by 101 publications

(106 citation statements)

References 27 publications

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“…We use the Perdew–Burke–Ernzerhof exchange correlation functional and calculations are performed using both standard DFT and the DFT+ U approach to correct for the self-interaction error. We employ the rotationally invariant DFT+ U formulation of Dudarev44 and the effective Hubbard parameter ( U − J ) for the Fe 3 d states is taken as 3.8 eV as was employed in previous studies3745. The valence-electron wavefunctions are expanded in a plane wave basis with energies up to 400 eV and structural optimization is performed until forces are <0.01 eV Å −1 .…”

Section: Methodsmentioning

confidence: 99%

Atomic-scale structure and properties of highly stable antiphase boundary defects in Fe3O4

et al. 2014

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The complex and intriguing properties of the ferrimagnetic half metal magnetite (Fe3O4) are of continuing fundamental interest as well as being important for practical applications in spintronics, magnetism, catalysis and medicine. There is considerable speculation concerning the role of the ubiquitous antiphase boundary (APB) defects in magnetite, however, direct information on their structure and properties has remained challenging to obtain. Here we combine predictive first principles modelling with high-resolution transmission electron microscopy to unambiguously determine the three-dimensional structure of APBs in magnetite. We demonstrate that APB defects on the {110} planes are unusually stable and induce antiferromagnetic coupling between adjacent domains providing an explanation for the magnetoresistance and reduced spin polarization often observed. We also demonstrate how the high stability of the {110} APB defects is connected to the existence of a metastable bulk phase of Fe3O4, which could be stabilized by strain in films or nanostructures.

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Section: Methodsmentioning

confidence: 99%

Atomic-scale structure and properties of highly stable antiphase boundary defects in Fe3O4

et al. 2014

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“…Heating above 448 K leads to the diffusion of Ni into the bulk of the sample, and the restoration of the SCV termination. (111), which can be compared to the 0.95 eV on the Fe tet1 termination [296] . An even bigger difference was found on the Fe oct2 termination (terminated by Fe, although Ni could also be possible here as it occupies octahedral sites), 2.30 eV vs 1.33 eV [535].…”

Section: Nickelmentioning

confidence: 99%

Iron oxide surfaces

Parkinson

2016

Surface Science Reports

501

463

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The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), hematite (α-Fe 2 O 3 ), and wüstite (Fe 1-x O) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe 3 O 4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment, and because it is an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed.The best understood iron oxide surface at present is probably Fe 3 O 4 (100); the structure is known with a high degree of precision and the major defects and properties are well characterised. A major factor in this is that a termination at the Fe oct -O plane can be reproducibly prepared by a variety of methods, as long as the surface is annealed in 10 Such straightforward preparation of a monophase termination is generally not the case for other iron oxide surfaces. All available evidence suggests the oft-studied (√2×√2)R45° reconstruction results from a rearrangement of the cation lattice in the outermost unit cell in which two octahedral cations are replaced by one tetrahedral interstitial, a motif conceptually similar to well-known Koch-Cohen defects in Fe (0001) is the most studied hematite surface, but 2 difficulties preparing stoichiometric surfaces under UHV conditions have hampered a definitive determination of the structure. There is evidence for at least three terminations: a bulk-like termination at the oxygen plane, a termination with half of the cation layer, and a termination with ferryl groups. When the surface is reduced the so-called "bi-phase" structure is formed, which eventually transforms to a Fe 3 O 4 (111)-like termination. The structure of the bi-phase surface is controversial; a largely accepted model of coexisting Fe 1-x O and α-Fe 2 O 3 (0001) islands was recently challenged and a new structure based on a thin film of Fe 3 O 4 (111) on α-Fe 2 O 3 (0001) was proposed. The merits of the compet...

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“…It is reported that for correct description of the interaction of small molecules with the Fe 3 O 4 surface, e.g. ; atomic H with the Fe 3 O 4 (0 0 1) [10,11], and H 2 O with Fe 3 O 4 surface [12][13][14][15], it is necessary to include the Hubbard parameter (U) for the on-site Coulomb interaction of the Fe 3d electrons (DFT + U) [16]. Using scanning tunneling (STM), DFT + U and XPS, Parkinson et al [10] and Kurahashi et al [11] studied atomic H adsorption on the Fe 3 O 4 (1 0 0) surface and found that at saturation coverage the insulating ( √ 2 × √ 2)R45 • reconstruction is lifted and the surface undergoes a semiconductor-half metal transition.…”

Section: Introductionmentioning

confidence: 99%