Why is EXAFS for complex concentrated alloys so hard? Challenges and opportunities for measuring ordering with X-ray absorption spectroscopy

Joress, Howie; Ravel, Bruce; Anber, Elaf; Hollenbach, Jonathan; Sur, Debashish; Hattrick-Simpers, Jason; Taheri, Mitra L.; DeCost, Brian

doi:10.1016/j.matt.2023.09.010

Cited by 7 publications

(1 citation statement)

References 55 publications

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“…In those cases, the objective method shows a high potential to study the local structure correctly. The potential of this method is not limited to UF 4 and other molten salts, and can be expanded to other fields, such as the Co 2+ ions doping in a nanostructural glass, where different Co local geometry can result in optical property changes, complex concentrated alloys, where EXAFS fails to capture local structure, and some biological catalysts, such as enzymes with specific metal active sites. − However, the current method still needs improvement, such as by improving the speed and efficiency of objective structure generation.…”

Section: Discussionmentioning

confidence: 99%

Decoding the Pair Distribution Function of Uranium in Molten Fluoride Salts from X-Ray Absorption Spectroscopy Data by Machine Learning

Zheng,

Marcella,

Smith

et al. 2024

J. Phys. Chem. C

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Thermal properties of actinides in molten salts are linked to the strongly disordered local environment of actinide ions. We illustrate both the limitations of the commonly used fitting method for analysis of extended X-ray absorption fine structure (EXAFS) spectra in molten UF 4 and a possible solution using an "objective neural network-EXAFS" (ONNE) method. ONNE provides both extraction of the pair distribution function, as validated by its application to the EXAFS spectra calculated on molecular dynamics trajectory, and the EXAFS data reconstruction. The ONNE analysis of the molten UF 4 has revealed reduction of the first nearest neighbor U−F coordination number, expansion of the U−F bond length, and smaller contribution to the second shell compared to current molecular dynamics models. This method is therefore an attractive alternative to conventional EXAFS analysis and molecular dynamics simulations for studies of disordered environment of actinides in molten salts.

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Section: Discussionmentioning

confidence: 99%

Decoding the Pair Distribution Function of Uranium in Molten Fluoride Salts from X-Ray Absorption Spectroscopy Data by Machine Learning

Zheng,

Marcella,

Smith

et al. 2024

J. Phys. Chem. C

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In Situ X‐Ray Absorption Studies on Local Structure of Annealed Metallic Glasses FeGaB and FeCoSiB

Hayen,

Jordt,

Hövelmann

et al. 2024

Physica Status Solidi (a)

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The microscopic structure of Fe‐based metallic glasses (FeGaB) and (FeCoSiB) is investigated during in situ thermal annealing using extended X‐ray absorption fine structure spectroscopy (EXAFS) above the Fe–K and Co–K absorption edges. FeGaB exhibits a phase transition above 450 °C, changing from amorphous glass to a partially crystalline structure. Its medium‐range structure after this transition is modeled from crystalline α‐Fe and reference structures, combined with amorphous nearest‐neighbor (NN) contributions of . Local order in the glass phase is described with the same model, restricted to NN interactions. Changes in the amorphous structure occur at annealing temperatures which coincide with typical observations of changes in magnetic behavior. Meanwhile, in FeCoSiB, the EXAFS response is highly different between the Fe–K and Co–K absorption edges. EXAFS oscillations on the Fe edge are strongly suppressed, as opposed to the Co edge which shows typical amplitudes. Limited resolution in this data set allows modeling only in the first amorphous shell, based on the NN distances from FeCo. The cause of the two materials’ different EXAFS behavior at Fe–K despite similar iron content and identical experimental conditions is currently unknown and subject of further investigation.

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Deciphering the Local Environment of Electrocatalytic Metal Sites with X‐ray Absorption Fine Structure

Zhang,

Wang

2024

Small Structures

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Electrocatalysis plays a pivotal role in energy conversion and holds significant promise for the development of new energy sources. Understanding the intricate atomic‐level interplay between active sites and electrocatalytic activity is essential for comprehending catalytic behavior and advancing high‐performance catalysts. In this review, an overview of the recent advances in X‐ray absorption fine structure (XAFS) is provided for deciphering the local environment of electrocatalytic metal sites. The application of XAFS in disclosing the electronic interaction and coordination environment of metal sites is summarized, offering insights into the correlation between ligand arrangement and catalytic activity. Special attention is given to advanced XAFS techniques for exploring active species, including determining the actual active sites, monitoring the local structure transformation, and deciphering metal sites–catalysis relationship. The limitations of traditional XAFS have naturally prompted the development of high‐spatiotemporal‐resolution and high‐energy‐resolution techniques as well as in‐situ/operando methods to better understand the entire catalytic process. This review is anticipated to provide a comprehensive understanding of the capabilities of XAFS in exploring the fine structure of electrocatalysts, with implications for the design of advanced catalytic materials.

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Why is EXAFS for complex concentrated alloys so hard? Challenges and opportunities for measuring ordering with X-ray absorption spectroscopy

Cited by 7 publications

References 55 publications

Decoding the Pair Distribution Function of Uranium in Molten Fluoride Salts from X-Ray Absorption Spectroscopy Data by Machine Learning

Decoding the Pair Distribution Function of Uranium in Molten Fluoride Salts from X-Ray Absorption Spectroscopy Data by Machine Learning

In Situ X‐Ray Absorption Studies on Local Structure of Annealed Metallic Glasses FeGaB and FeCoSiB

Deciphering the Local Environment of Electrocatalytic Metal Sites with X‐ray Absorption Fine Structure

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