Local Environments in Iron-Bearing Clay Minerals by DFT Approaches: The Case of Structural Fe in Kaolinite

Richard, Diego; Rendtorff, Nicolás M.

doi:10.1016/j.clay.2021.106251

Cited by 19 publications

(11 citation statements)

References 69 publications

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“…The energy difference between Fe 2+ spin states is significant (~ 60-70 kJ/mol), indicating a preferable possibility of only the high spin state. While the energy difference of low and high spin state of Fe 3+ is quite small (~ 7 kJ/mol), the calculated Boltzmann distribution indicate the almost exclusive presence of high spin states for both Fe 2+ and Fe 3+ , which is in agreement with the literature [4,19].…”

Section: Computational Chemistrysupporting

confidence: 90%

“…Computational chemistry was utilized to probe the molecular structure of kaolinite with structural iron. The computational study of Richard et al showed that the utilization of GIPAW-D2 + method could describe the electronic structure of Al substituted for Fe atom and together with the Mössbauer data, it had been found that the both Fe 3+ and Fe 2+ can exist in the kaolinite layers, but only in high spin state form [19].…”

Section: Computational Chemistrymentioning

confidence: 99%

“…The rare isomorphous substitution of Al to Fe in kaolinites could also play an important role in the improvement of intrinsic photocatalytic properties [15]. Iron substitution in clays is considered to follow a random distribution [16], and while Fe 3+ and rarely Fe 2+ can be found in the O-sheet, only Fe 3+ is reported in the T-sheet [17][18][19]. Fe 3+ generally retains the six-fold coordination [20], while Fe 2+ can be present in six-or four-fold coordinations [21,22] as well.…”

Section: Introductionmentioning

confidence: 99%

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Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Zsirka

Győrfi

Yamaguchi

et al. 2022

Journal of Materials Research

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Nanoscroll formation by casacade intercalation–exfoliation method was investigated for a high iron-content kaolin and after the removal of its iron-bearing mineral constituents (goethite, hematite) by 11 M HCl treatment. Hindered kaolinite nanoscroll formation was observed by TEM in both cases, where the 11 M HCl treatment only slightly improved the occurrence of nanoscrolled shapes. The presence of minor amounts of well-dispersed, resilient Fe was observed after the exfoliation of 11 M HCl-treated sample, which was identified as structural Fe3+/Fe2+ in the octahedral sheet of kaolinite by Mössbauer and X-ray absorption spectroscopy. Iron substitution in the nanokaolinite TO layers was probed by computational chemistry. The computational results indicate inner coordination changes and elongation of bonds in the iron-substituted TO structure, and the increased curvature values offer an explanation for the observed experimental results for hindered nanoscroll formation. Graphical abstract

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Section: Computational Chemistrysupporting

confidence: 90%

Section: Computational Chemistrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Zsirka

Győrfi

Yamaguchi

et al. 2022

Journal of Materials Research

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“…In order to get closer to the real kaolinite minerals, researchers have carried out lattice substitution in perfect phases, such as replacing Al in the octahedron with Fe, Mg, or Mn, etc. [91][92][93] . On the other hand, in DFT simulation calculation, the number of adsorbed water molecules is limited, which is far from the real clay-water system.…”

Section: Computational Model Idealizationmentioning

confidence: 99%

Molecular simulation in surface hydration of clay minerals: a review of theory and applications

Min¹,

Wang²,

Liu³

et al. 2022

Miner Miner Mater

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Clay minerals, which are prevalent gangue minerals, are found in tailings and beneficiation effluent after the extraction of valuable minerals. The surface of clay mineral particles is easy to hydrate, which makes it the main factor restricting tailings separation and wastewater treatment. However, the microscopic mechanism of clay mineral particle surface hydration is not yet systematic. In recent years, with the development of molecular simulation theory and the improvement of computational efficiency, density functional theory (DFT) and molecular dynamics (MD) have gradually become a powerful tool for studying the surface hydration of clay mineral particles, which provides new insight into the interaction between the crystal structures of clay minerals and the interfacial interaction in surface hydration of clay mineral particles at the molecular or atomic levels. This article first reviews the basic theory of DFT and MD, then reviews the research progress on clay mineral surface hydration. From the perspective of molecular simulation, a comprehensive discussion of the clay mineral phase structure, the establishment of the supercell surface model, the clay-water interface interaction and the limitations of molecular simulation was conducted. Water molecules can adsorb with different mineral surfaces in slime water through hydrogen bond, which is the basis of surface hydration mechanism. The hydration layer is composed of three water layers with different densities, with a thickness of about 8-10 Å. Water and ions form hydrate cations, which are adsorbed on the surface of clay minerals, change the structure of water layer on the surface of minerals. This article ends with a brief discussion of conclusions and perspectives.

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“…SSNMR can detect detailed structural differences of 133 Cs, but the NMR parameters in relation to local structures are not yet fully understood. A reasonable degree of success has been achieved by comparing experimental data with NMR calculations based on model structures. − For example, a linear relationship between the interlayer distance and 133 Cs δ iso has been reported from a series of model structures with various interlayer spaces . The chemical shift is toward the low-field state due to the neighboring negatively charged Al sites on a tetrahedral sheet.…”

Section: Introductionmentioning

confidence: 99%

New Approach To Understanding the Experimental ¹³³Cs NMR Chemical Shift of Clay Minerals via Machine Learning and DFT-GIPAW Calculations

et al. 2023

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Structural determination of adsorbed atoms on layered structures such as clay minerals is a complex subject. Radioactive cesium (Cs) is an important element for environmental conservation, so it is vital to understand its adsorption structure on clay. The nuclear magnetic resonance (NMR) parameters of 133 Cs, which can be determined from solid-state NMR experiments, are sensitive to the local neighboring structures of adsorbed Cs. However, determining the Cs positions from NMR data alone is difficult. This paper describes an approach for identifying the expected atomic positions on clay minerals by combining machine learning (ML) with experimentally observed chemical shifts. A linear ridge regression model for ML is constructed from the smooth overlap of atomic position descriptor and gauge-including projector augmented wave (GIPAW) ab initio data. The constructed ML model predicts the GIPAW data to within a 3 ppm root-mean-squared error. At this stage, the 133 Cs chemical shifts can be instantaneously calculated from the Cs positions on any clay layers using ML. The inverse analysis, which derives the atomic positions from experimentally observed chemical shifts, is developed from the ML model. The input data for the inverse analysis are the layer structure and the experimentally observed chemical shifts. The Cs positions for the targeted chemical shifts are then output. Inverse analysis is applied to montmorillonite, and the resultant Cs positions are found to be consistent with previous results (Ohkubo, T.; et al. J. Phys. Chem. A 2018, 122, 9326−9337). The Cs positions on saponite clay are also clarified from experimentally observed chemical shifts and inverse analysis.

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Local Environments in Iron-Bearing Clay Minerals by DFT Approaches: The Case of Structural Fe in Kaolinite

Cited by 19 publications

References 69 publications

Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Molecular simulation in surface hydration of clay minerals: a review of theory and applications

New Approach To Understanding the Experimental ¹³³Cs NMR Chemical Shift of Clay Minerals via Machine Learning and DFT-GIPAW Calculations

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Local Environments in Iron-Bearing Clay Minerals by DFT Approaches: The Case of Structural Fe in Kaolinite

Cited by 19 publications

References 69 publications

Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Effect of structural iron on nanoscroll formation via exfoliation of a high iron-content kaolin

Molecular simulation in surface hydration of clay minerals: a review of theory and applications

New Approach To Understanding the Experimental 133Cs NMR Chemical Shift of Clay Minerals via Machine Learning and DFT-GIPAW Calculations

Contact Info

Product

Resources

About

New Approach To Understanding the Experimental ¹³³Cs NMR Chemical Shift of Clay Minerals via Machine Learning and DFT-GIPAW Calculations