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X-ray Absorption Fine Structure and Symmetry

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A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Chemistry: Symmetry/Asymmetry".

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 10938

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Special Issue Editors

Prof. Dr. Takafumi Miyanaga

E-Mail Website
Guest Editor

Department of Mathematics and Physics, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
Interests: XAFS; synchrotron radiation; phase transition; magnetism; nanoparticles; chemical reaction; functional materials

Prof. Dr. Keisuke Hatada

E-Mail Website
Guest Editor

Department of Physics, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
Interests: XAFS; synchrotron radiation; photoelectron diffraction; XFEL

Special Issue Information

Dear Colleagues,

Symmetry is one of the most important concepts in natural science. It lies at the heart of fundamental laws of nature and is an important tool for understanding the properties of complex systems including condensed matter physics, materials science, and technology. The concept of symmetry plays an important role in phase transition, exotic electronic structure, and chemical reactivity in condensed matter and chemical systems.

The other trend, which has been developed in recent years along with synchrotron radiation sources, X-ray absorption fine structure (XAFS) is becoming a powerful technique to study the local atomic structure, electronic structure, and structure dynamics for ferroelectric and magnetic materials, semiconductors, molecules, and gas-phase systems. XAFS is a hybrid technique to study both structure and electronic state, which is strongly correlated with the symmetry in the condensed matter. We will discuss the physical properties and chemical reactivities of modern functional materials from the symmetry point of view, which has a key concept of recent industrial innovation. Symmetry is also an important idea for the development of the theory of XAFS. This Special Issue will emphasize the phenomena that lie at the crossroads between the concept of symmetry and several functions of materials, including the structure analysis techniques.

Prof. Dr. Takafumi Miyanaga
Prof. Dr. Keisuke Hatada
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

X-ray absorption fine structure (XAFS)
theory of XANES
phase transitions
electronic structure
ferroelectric materials
magnetic materials
semiconductors
chemical reactivity
catalytic reaction
optical property
metalloprotein

Published Papers (6 papers)

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Research

Jump to: Review

13 pages, 2581 KiB

Open AccessArticle

Synthesis, Crystal Structure, Local Structure, and Magnetic Properties of Polycrystalline and Single-Crystalline Ce₂Pt₆Al₁₅

by Kyugo Ota, Yuki Watabe, Yoshinori Haga, Fabio Iesari, Toshihiro Okajima and Yuji Matsumoto

Symmetry 2023, 15(8), 1488; https://0-doi-org.brum.beds.ac.uk/10.3390/sym15081488 - 27 Jul 2023

Cited by 2 | Viewed by 912

Abstract

Asymmetry, such as non-centrosymmetry in the crystal or chiral structure and local symmetry breaking, plays an important role in the discovery of new phenomena. The honeycomb structure is an example of an asymmetric structure. Ce

_{2}

_{6}

_{15}

is a candidate [...] Read more.

_{2}

_{6}

_{15}

is a candidate for a frustrated system with honeycomb Ce-layers, which have been reported to show near the quantum critical point. However, the ground state of Ce

_{2}

_{6}

_{15}

depends on the sample, and analysis of the crystal structure is difficult due to the presence of stacking disorder. We synthesized polycrystalline Ce

_{2}

_{6}

_{15}

using arc melting method (AM-Ce

_{2}

_{6}

_{15}

) and single-crystalline Ce

_{2}

_{6}

_{15}

using flux method (F-Ce

_{2}

_{6}

_{15}

). The prepared samples were characterized by electron probe micro-analysis (EPMA), single and powder X-ray diffraction methods, measured magnetic properties and X-ray absorption spectroscopy (XAS). The composition ratio of AM-Ce

_{2}

_{6}

_{15}

was stoichiometric, although it contained a small amount (i.e., a few percent) of the impurity Ce

_{2}

_{9}

_{16}

. Meanwhile, the composition ratio of F-Ce

_{2}

_{6}

_{15}

deviated from stoichiometry. The X-ray absorption fine structure (XAFS) spectrum of AM-Ce

_{2}

_{6}

_{15}

at the Ce L

_{3}

-edge was similar to that of CeF

_{3}

, which possesses the Ce

^{3 +}

configuration, indicating that the valence of Ce in Ce

_{2}

_{6}

_{15}

is trivalent; this result is consistent with that for the magnetic susceptibility. To determine the precise structure, we analyzed the extended X-ray absorption fine structure (EXAFS) spectra of Ce L

_{3}

- and Pt L

_{3}

-edges for Ce

_{2}

_{6}

_{15}

, and found that the EXAFS spectra of Ce

_{2}

_{6}

_{15}

can be explained not as a hexagonal Sc

_{0.6}

_{2}

_{4.9}

-type structure but, instead, as an orthorhombic structure with honeycomb structure. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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11 pages, 482 KiB

Open AccessFeature PaperArticle

First-Principles Calculation of Ligand Field Parameters for L-Edge Spectra of Transition Metal Sites of Arbitrary Symmetry

by Peter Krüger

Symmetry 2023, 15(2), 472; https://0-doi-org.brum.beds.ac.uk/10.3390/sym15020472 - 10 Feb 2023

Cited by 2 | Viewed by 1157

Abstract

Recently we have proposed a simple method for obtaining the parameters of a ligand field multiplet model for L-edge spectra calculations from density functional theory. Here we generalize the method to systems where the metal site has arbitrary point symmetry. The ligand field-induced splitting of the metal d-level becomes a hermitian matrix with cross-terms between the different d-orbitals. The anisotropy of the covalency is fully taken into account and it rescales the electron–electron interaction and the oscillator strength in an orbital-dependent way. We apply the method to polarization-dependent V L-edge spectra of vanadium pentoxide and obtain very good agreement with the experiment. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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10 pages, 3078 KiB

Open AccessArticle

Base Catalysis of Sodium Salts of [Ta_6−xNb_xO₁₉]⁸⁻ Mixed-Oxide Clusters

by Soichi Kikkawa, Mio Tsukada, Kanako Shibata, Yu Fujiki, Kazuki Shibusawa, Jun Hirayama, Naoki Nakatani, Takafumi Yamamoto and Seiji Yamazoe

Symmetry 2021, 13(7), 1267; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13071267 - 15 Jul 2021

Cited by 4 | Viewed by 2136

Abstract

The solid base catalysis of sodium salts of Lindqvist-type metal oxide clusters was investigated using a Knoevenagel condensation reaction. We successfully synthesized the sodium salts of Ta and Nb mixed-oxide clusters Na_8−nH_n[(Ta_6−xNb_x)O₁₉]·15H₂O (Na-Ta_6−xNb_x, n = 0, 1, x = 0–6) and found them to exhibit activity for proton abstraction from nitrile substrates with a pK_a value of 23.8, which is comparable to that of the conventional solid base MgO. The Ta-rich Na-Ta₆ and Na-Ta₄Nb₂ exhibited high activity among Ta and Nb mixed-oxide clusters. Synchrotron X-ray diffraction (SXRD) measurements, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray absorption spectroscopy (XAS) revealed the structure of Na-Ta_6−xNb_x: (1) The crystal structure changed from Na₇H[M₆O₁₉]·15H₂O to Na₈[M₆O₁₉]·15H₂O (M = Ta or Nb) by the anisotropic expansion of the unit cell with an increase in Ta content; (2) Highly symmetrical Lindqvist [Ta_6−xNb_xO₁₉]⁸⁻ was generated in Na-Ta₄Nb₂ and Na-Ta₆ because of the symmetrical association of Na⁺ ions with [Ta_6−xNb_xO₁₉]⁸⁻ in the structure. DFT calculation revealed that the Lindqvist structures with high symmetry have large NBO charges on surface oxygen species, which are strongly related to base catalytic activity, whereas the composition hardly affects the NBO charges. The above results showed that the Brønsted base catalysis was sensitive to the symmetry of the Lindqvist [Ta_6−xNb_xO₁₉]⁸⁻ structure. These findings contribute to the design of solid base catalysts composed of anionic metal oxide clusters with alkaline-metal cations. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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10 pages, 418 KiB

Open AccessFeature PaperArticle

Extracting Local Symmetry of Mono-Atomic Systems from Extended X-ray Absorption Fine Structure Using Deep Neural Networks

by Fabio Iesari, Hiroyuki Setoyama and Toshihiro Okajima

Symmetry 2021, 13(6), 1070; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13061070 - 15 Jun 2021

Cited by 2 | Viewed by 1905

Abstract

In recent years, neural networks have become a new method for the analysis of extended X-ray absorption fine structure data. Due to its sensitivity to local structure, X-ray absorption spectroscopy is often used to study disordered systems and one of its more interesting property is the sensitivity not only to pair distribution function, but also to three-body distribution, which contains information on the local symmetry. In this study, by considering the case of Ni, we show that by using neural networks, it is possible to obtain not only the radial distribution function, but also the bond angle distribution between the first nearest-neighbors. Additionally, by adding appropriate configurations in the dataset used for training, we show that the neural network is able to analyze also data from disordered phases (liquid and undercooled state), detecting small changes in the local ordering compatible with results obtained through other methods. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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12 pages, 1941 KiB

Open AccessFeature PaperArticle

Relativistic Corrections to Phase Shift Calculation in the GNXAS Package

by Nodoka Hara, Andrea Di Cicco, Georghii Tchoudinov, Keisuke Hatada and Calogero Renzo Natoli

Symmetry 2021, 13(6), 1021; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13061021 - 06 Jun 2021

Cited by 3 | Viewed by 1984

Abstract

Modern XAFS (X-ray Absorption Fine Structure) data-analysis is based on accurate multiple-scattering (MS) calculations of the X-ray absorption cross-section. In this paper, we present the inclusion and test of relativistic corrections for the multiple-scattering calculations within the GnXAS suite of programs, which is relevant to the treatment of the XAFS signals when atoms with high atomic number are contained into the system. We present a suitable strategy for introducing relativistic corrections without altering the basic structure of the programs. In particular, this is realized by modifying only the Phagen program calculating the atomic absorption cross sections and scattering t-matrices for the selected cluster. The modification incorporates a pseudo-Schrödinger Equation (SE) replacing the Dirac relativistic form. The phase-shift calculations have been put to a test in two known molecular and crystalline cases: molecular bromine Br

_{2}

and crystalline Pb. Calculations in an extended energy range have been shown to be very close to the non-relativistic case for Br

_{2}

(Br K-edge) while corrections have been found to exceed 25% for amplitude and phases of the XAFS multiple-scattering signals (Pb L

_{3}

-edge). Benefits in the structural refinement using relativistic corrections are discussed for crystalline Pb at room temperature. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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Review

Jump to: Research

11 pages, 2170 KiB

Open AccessReview

Local Structure and Dynamics of Functional Materials Studied by X-ray Absorption Fine Structure

by Takafumi Miyanaga

Symmetry 2021, 13(8), 1315; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13081315 - 22 Jul 2021

Cited by 4 | Viewed by 1777

Abstract

X-ray absorption fine structure (XAFS) is a powerful technique used to analyze a local electronic structure, local atomic structure, and structural dynamics. In this review, I present examples of XAFS that apply to the local structure and dynamics of functional materials: (1) structure phase transition in perovskite PbTiO₃ and magnetic FeRhPd alloys; (2) nano-scaled fluctuations related to their magnetic properties in Ni–Mn alloys and Fe/Cr thin films; and (3) the Debye–Waller factors related to the chemical reactivity for catalysis in polyanions and ligand exchange reaction. This study shows that the local structure and dynamics are related to the characteristic function of the materials. Full article

(This article belongs to the Special Issue X-ray Absorption Fine Structure and Symmetry)

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