High-temperature X-ray absorption spectroscopy study of thermochromic copper molybdate

Jonane, Inga; Anspoks, Andris; Aquilanti, Giuliana; Kuzmin, Alexei

doi:10.1016/j.actamat.2019.06.034

Cited by 18 publications

(13 citation statements)

References 54 publications

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“…Nevertheless, we fully expect that this limitation can be addressed with the inclusion of order parameters for additional motifs in future and retraining of the models. Finally, although temperature can have a pronounced effect on XANES, 53 we did not explicitly consider its effect in this work, although we expect that the data-augmentation procedure would have accounted for it to some extent.…”

Section: Discussionmentioning

confidence: 99%

Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure

Chen

et al. 2020

Patterns

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Analyzing coordination environments using X-ray absorption spectroscopy has broad applications ranging from solid-state physics to material chemistry. Here, we show that random forest models can identify the main coordination environment from K-edge Xray absorption near edge structure (XANES) with a high accuracy of 85.4% and all associated coordination environments with a high Jaccard score of 81.8% for 33 cation elements in oxides, significantly outperforming other machine learning (ML) models.In a departure from prior works, we used a robust description of the coordination environment as a distribution over 25 distinct coordination motifs with coordination numbers ranging from 1-12. The random forest models were trained on the world's largest database of ∼ 190, 000 computed K-edge XANES spectra. Furthermore, the random forest models can be applied to predict the coordination environment from experimental K-edge XANES with minimal loss in accuracy (82.1%) due to the use of data augmentation. A drop-out feature importance analysis highlights the key roles that the pre-edge and main-peak regions play in coordination environment identification, with the post-peak region becoming increasingly important at higher coordination numbers.This work provides a general strategy to identify the coordination environment from K-edge XANES across broad chemistries, paving the way for future advancements in the application of ML to spectroscopy.

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Section: Discussionmentioning

confidence: 99%

Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure

Chen

et al. 2020

Patterns

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“…1) [1,5,11]. The similar color change occurs also in α-CuMoO 4 on heating [12], however, in this case, no phase transition takes place, the coordination of metal ions remains unchanged, and the variation of color is due to the lattice expansion and strong enhancement of specific thermal disorder [13]. For tungsten content above x ∼ 0.15, CuMo 1−x W x O 4 solid solutions crystallize in the wolframite-type structure with the octahedral coordination of metal ions and do not manifest pronounced thermochromic behaviour.…”

Section: Introductionmentioning

confidence: 59%

Study of the thermochromic phase transition in CuMo$_{1-x}$W$_x$O$_4$ solid solutions at the W L$_3$-edge by resonant X-ray emission spectroscopy

Pudza,

Kalinko,

Cintins

et al. 2020

Preprint

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Polycrystalline CuMo 1−x W x O 4 solid solutions were studied by resonant X-ray emission spectroscopy (RXES) at the W L 3 -edge to follow a variation of the tungsten local atomic and electronic structures across thermochromic phase transition as a function of sample composition and temperature. The experimental results were interpreted using ab initio calculations. The crystal-field splitting parameter ∆ for the 5d(W)-states was obtained from the analysis of the RXES plane and was used to evaluate the coordination of tungsten atoms.Temperature-dependent RXES measurements were successfully employed to determine the hysteretic behaviour of the structural phase transition between the α and γ phases in CuMo 1−x W x O 4 solid solutions on cooling and heating, even at low (x < 0.10) tungsten content. It was found that tungsten ions

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“…This damping is due to an increased amplitude of the incoherent vibrational motion of atoms in a warmer lattice, and can be accounted for using a Debye-Waller (DW) factor. 37,38 No changes in the frequency of the EXAFS modulations are observed implying that no significant bond length changes occur in the vicinity of the Zn atoms after photoexcitation. The transient EXAFS can thus be used to accurately calibrate the lattice temperature as a result of laser heating, which is then used in the analysis of the transient XANES spectrum.…”

Section: Resultsmentioning

confidence: 99%

Charge Carrier Screening in Photoexcited Epitaxial Semiconductor Nanorods Revealed by Transient X-ray Absorption Linear Dichroism

et al. 2021

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Understanding the electronic structure and dynamics of semiconducting nanomaterials at the atomic level is crucial for the realization and optimization of devices in solar energy, catalysis, and optoelectronic applications. We report here on the use of ultrafast X-ray linear dichroism spectroscopy to unravel the carrier dynamics in epitaxial ZnO nanorods after band-gap photoexcitation. By rigorously subtracting out thermal contributions and conducting ab initio calculations, we reveal an overall depletion of absorption cross sections in the transient X-ray spectra caused by photogenerated charge carriers screening the core-hole potential of the X-ray absorbing atom. At low laser excitation densities, we observe phase-space filling by excited electrons and holes separately. These results pave the way for carrier-and element-specific probing of charge transfer dynamics across heterostructured interfaces with ultrafast table-top and fourth generation X-ray sources.

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High-temperature X-ray absorption spectroscopy study of thermochromic copper molybdate

Cited by 18 publications

References 54 publications

Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure

Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure

Study of the thermochromic phase transition in CuMo$_{1-x}$W$_x$O$_4$ solid solutions at the W L$_3$-edge by resonant X-ray emission spectroscopy

Charge Carrier Screening in Photoexcited Epitaxial Semiconductor Nanorods Revealed by Transient X-ray Absorption Linear Dichroism

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