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1. Potassium and Calcium K ‐Edge XANES in Chemical Compounds and Minerals: Implications for Geological Phase Identification

   https://doi.org/10.1111/ggr.12351  

   Li, Wenshuai; Liu, Xiao‐Ming; Hu, Yongfeng (August 2020, Geostandards and Geoanalytical Research)

   Potassium (K) and calcium (Ca)K‐edge X‐ray adsorption near‐edge (XANES) spectroscopy were performed on thirty‐three chemical compounds and geological materials, including chemical reagents, organometallic compounds, silicates, carbonates and igneous rock reference materials. The results confirm that the fine structure of theK‐edges for specimens is unique and distinguishable. The results suggest that compositional and local atomic variations strongly regulate spectral characteristics. Acquired XANES spectra with the library of distinctive spectral features of model references approve the fingerprint identification of different phases of K and Ca involved in geological materials. Moreover, this reveals that typical compositional changes in geological samples could strongly affect spectral features. As an example, we quantitatively determined the silicate species of K and Ca in two igneous rock reference materials by linear combination fitting. The dominant hosts and molecular environments of K and Ca can be interpreted based on pre‐edge/post‐edge peak position, intensity, shifts and resonance features, thus improving the understanding of the (bio)geochemical cycling, partitioning and isotopic fractionation of K and Ca. The outcomes serve as a complementary database for a vast number of scientific contexts, including aspects of geological and environment sciences. 

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2. Database of ab initio L-edge X-ray absorption near edge structure

   https://doi.org/10.1038/s41597-021-00936-5  

   Chen, Yiming; Chen, Chi; Zheng, Chen; Dwaraknath, Shyam; Horton, Matthew K.; Cabana, Jordi; Rehr, John; Vinson, John; Dozier, Alan; Kas, Joshua J.; et al (June 2021, Scientific Data)

   Abstract The L-edge X-ray Absorption Near Edge Structure (XANES) is widely used in the characterization of transition metal compounds. Here, we report the development of a database of computed L-edge XANES using the multiple scattering theory-based FEFF9 code. The initial release of the database contains more than 140,000 L-edge spectra for more than 22,000 structures generated using a high-throughput computational workflow. The data is disseminated through the Materials Project and addresses a critical need for L-edge XANES spectra among the research community. 

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3. Zn ₂ MnSbO ₆ and Zn ₂ FeSbO ₆ : Two New Polar High-Pressure Ordered Corundum-Type Compounds

   https://doi.org/10.1021/acs.chemmater.4c02146  

   Provino, Alessia; Emge, Thomas J; Walker, David; Frank, Corey E; Yoshida, Suguru; Gopalan, Venkatraman; Croft, Mark; Deng, Zheng; Jin, Changqing; Manfrinetti, Pietro; et al (December 2024, Chemistry of Materials)

   Two new compounds, Zn2FeSbO6 and Zn2MnSbO6, have been synthesized under high-pressure and high-temperature conditions. The synthesis, single-crystal and powder X-ray diffraction, X-ray absorption near-edge spectroscopy (XANES), optical second harmonic generation (SHG), and magnetic and heat capacity measurements were carried out for both compounds and are described. The lattice parameters are a = 5.17754(6) Å and c = 13.80045(16) Å for Zn2FeSbO6 and a = 5.1889(10) Å and c = 14.0418(3) Å for Zn2MnSbO6. Single-crystal X-ray diffraction analyses indicate that Zn2FeSbO6 consists of a cocrystal of superimposed Ni3TeO6 (NTO) and ordered ilmenite (OIL) components with a ratio of approximately 2:1 and Zn2MnSbO6 contains two nearly identical, but noncrystallographically related, OIL components in a ratio of approximately 6:1. 

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4. Magnetic ordering in a vanadium-organic coordination polymer using a pyrrolo[2,3- d :5,4- d ′]bis(thiazole)-based ligand

   https://doi.org/10.1039/C8RA05697H  

   Getmanenko, Yulia A.; Mullins, Christopher S.; Nesterov, Vladimir N.; Lake, Stephanie; Risko, Chad; Johnston-Halperin, Ezekiel (October 2018, RSC Advances)

   Here we present the synthesis and characterization of a hybrid vanadium-organic coordination polymer with robust magnetic order, a Curie temperature T C of ∼110 K, a coercive field of ∼5 Oe at 5 K, and a maximum mass magnetization of about half that of the benchmark ferrimagnetic vanadium(tetracyanoethylene) ∼2 (V·(TCNE) ∼2 ). This material was prepared using a new tetracyano-substituted quinoidal organic small molecule 7 based on a tricyclic heterocycle 4-hexyl-4 H -pyrrolo[2,3- d :5,4- d ′]bis(thiazole) ( C6-PBTz ). Single crystal X-ray diffraction of the 2,6-diiodo derivative of the parent C6-PBTz , showed a disordered hexyl chain and a nearly linear arrangement of the substituents in positions 2 and 6 of the tricyclic core. Density functional theory (DFT) calculations indicate that C6-PBTz -based ligand 7 is a strong acceptor with an electron affinity larger than that of TCNE and several other ligands previously used in molecular magnets. This effect is due in part to the electron-deficient thiazole rings and extended delocalization of the frontier molecular orbitals. The ligand detailed in this study, a representative example of fused heterocycle aromatic cores with extended π conjugation, introduces new opportunities for structure–magnetic-property correlation studies where the chemistry of the tricyclic heterocycles can modulate the electronic properties and the substituent at the central N -position can vary the spatial characteristics of the magnetic polymer. 

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5. Raman spectroscopy of phonon states in NbTe ₄ and TaTe ₄ quasi‐one‐dimensional van der Waals crystals

   https://doi.org/10.1002/jrs.6661  

   Nataj, Zahra_Ebrahim; Kargar, Fariborz; Krylyuk, Sergiy; Debnath, Topojit; Taheri, Maedeh; Ghosh, Subhajit; Zhang, Huairuo; Davydov, Albert_V; Lake, Roger_K; Balandin, Alexander_A (February 2024, Journal of Raman Spectroscopy)

   Abstract We report the results of polarization‐dependent Raman spectroscopy of phonon states in single‐crystalline quasi‐one‐dimensional NbTe₄and TaTe₄van der Waals materials. The measurements were conducted in the wide temperature range from 80 to 560 K. Our results show that although both materials have identical crystal structures and symmetries, there is a drastic difference in the intensity of their Raman spectra. While TaTe₄exhibits well‐defined peaks through the examined wavenumber and temperature ranges, NbTe₄reveals extremely weak Raman signatures. The measured spectral positions of the phonon peaks agree with the phonon band structure calculated using the density‐functional theory. We offer possible reasons for the intensity differences between the two van der Waals materials. Our results provide insights into the phonon properties of NbTe₄and TaTe₄van der Waals materials and indicate the potential of Raman spectroscopy for studying charge‐density‐wave quantum condensate phases. 

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