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1. Ca ₂ Ga ₄ Ge ₆ and Ca ₃ Ga ₄ Ge ₆ : Synthesis, Structure, and Electronic Properties

   https://doi.org/10.1002/zaac.202100342  

   Hodge, Kelsey L; Davis, H Olivia; Koster, Karl G; Windl, Wolfgang; Moore, Curtis E; Goldberger, Joshua E (August 2022, Zeitschrift für anorganische und allgemeine Chemie)

   Abstract During the search for transition metal‐free alkyne hydrogenation catalysts, two new ternary Ca−Ga−Ge phases, Ca₂Ga₄Ge₆(Cmc2₁, a=4.1600(10) Å, b=23.283(5) Å, c=10.789(3) Å) and Ca₃Ga₄Ge₆(C2/m, a=24.063(2) Å, b=4.1987(4) Å, c=10.9794(9) Å, β=91.409(4)°), were discovered. These compounds are isostructural to the previously established Yb₂Ga₄Ge₆and Yb₃Ga₄Ge₆analogues, and according to Zintl‐Klemm counting rules, consist of anionic [Ga₄Ge₆]⁴⁻and [Ga₄Ge₆]⁶⁻frameworks in which every Ga and Ge atom would have a formal octet with no Ga−Ga or Ga−Ge π‐bonding. These compounds are metallic, based on temperature dependent electrical resistivity and thermopower measurements for Ca₃Ga₄Ge₆, along with density functional theory calculations for both phases. Unlike the highly active 13‐layer trigonal CaGaGe phase, these new compounds exhibit minimal activity in the semi/full alkyne hydrogenation of phenylacetylene, which is consistent with previous observations that the lack of a formal octet for framework atoms is essential for catalysis in these Zintl‐Klemm compounds. 

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2. Single crystal neutron and magnetic measurements of Rb ₂ Mn ₃ (VO ₄ ) ₂ CO ₃ and K ₂ Co ₃ (VO ₄ ) ₂ CO ₃ with mixed honeycomb and triangular magnetic lattices

   https://doi.org/10.1039/C9DT03389K  

   Smith Pellizzeri, Tiffany M.; Sanjeewa, Liurukara D.; Pellizzeri, Steven; McMillen, Colin D.; Garlea, V. Ovidiu; Ye, Feng; Sefat, Athena S.; Kolis, Joseph W. (April 2020, Dalton Transactions)

   null (Ed.)

   Two new alkali vanadate carbonates with divalent transition metals have been synthesized as large single crystals via a high-temperature (600 °C) hydrothermal technique. Compound I , Rb 2 Mn 3 (VO 4 ) 2 CO 3 , crystallizes in the trigonal crystal system in the space group P 3̄1 c , and compound II , K 2 Co 3 (VO 4 ) 2 CO 3 , crystallizes in the hexagonal space group P 6 3 / m . Both structures contain honeycomb layers and triangular lattices made from edge-sharing MO 6 octahedra and MO 5 trigonal bipyramids, respectively. The honeycomb and triangular layers are connected along the c -axis through tetrahedral [VO 4 ] groups. The MO 5 units are connected with each other by carbonate groups in the ab -plane by forming a triangular magnetic lattice. The difference in space groups between I and II was also investigated with Density Functional Theory (DFT) calculations. Single crystal magnetic characterization of I indicates three magnetic transitions at 77 K, 2.3 K, and 1.5 K. The corresponding magnetic structures for each magnetic transition of I were determined using single crystal neutron diffraction. At 77 K the compound orders in the MnO 6 -honeycomb layer in a Néel-type antiferromagnetic orientation while the MnO 5 triangular lattice ordered below 2.3 K in a colinear ‘up–up–down’ fashion, followed by a planar ‘Y’ type magnetic structure. K 2 Co 3 (VO 4 ) 2 CO 3 ( II ) exhibits a canted antiferromagnetic ordering below T N = 8 K. The Curie–Weiss fit (200–350 K) gives a Curie–Weiss temperature of −42 K suggesting a dominant antiferromagnetic coupling in the Co 2+ magnetic sublattices. 

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3. Solvation Environment and Interface Dynamics of Li ₂ B ₁₂ H ₁₂ and Li ₂ B ₁₂ F ₁₂ Electrolytes Uncovered by Theory and Operando Optical and FTIR Spectroelectrochemistry

   https://doi.org/10.1021/acsami.4c14485  

   Simonyan, Hovnan; Zhong, Linda; Green, Matthew_M; Movsesyan, Khoren; Fraire, Andrew; Ward, Patrick_A; Lau, Kah_Chun; Teprovich, Jr., Joseph_A (December 2024, ACS Applied Materials & Interfaces)
4. Spin Dynamics and Phonons in Chromites CoCr ₂ O ₄ and MnCr ₂ O ₄

   https://doi.org/10.1088/0256-307X/41/11/117503  

   Xu_徐, Wei 威; Lin_林, Gaoting 高庭; Shu_舒, Mingfang 明方; Jiao_焦, Jinlong 金龙; Zhu_朱, Jinfeng 金峰; Ren_任, Qingyong 清勇; Le, Manh Duc; Luo_罗, Xuan 轩; Sun_孙, Yuping 玉平; Liu_刘, Yi 毅; et al (November 2024, Chinese Physics Letters)

   Abstract Spinel compounds are of great interest in both fundamental and application-oriented perspectives due to the geometric magnetic frustration inherent to their lattice and the resulting complex magnetic states. Here, we applied x-ray diffraction, magnetization, heat capacity and powder inelastic neutron scattering measurements, along with theoretical calculations, to study the exotic properties of chromite-spinel oxides CoCr₂O₄and MnCr₂O₄. The temperature dependence of the phonon spectra provides an insight into the correlation between oxygen motion and the magnetic order, as well as the magnetoelectric effect in the ground state of MnCr₂O₄. Moreover, spin-wave excitations in CoCr₂O₄and MnCr₂O₄are compared with Heisenberg model calculations. This approach enables the precise determination of exchange energies and offers a comprehensive understanding of the spin dynamics and relevant exchange interactions in complicated spiral spin ordering. 

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5. Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn ₄ (VO ₄ ) ₃ , Na ₂ Mn ₃ (VO ₄ ) ₃ , and Na ₂ Co ₃ (VO ₄ ) ₂ (OH) ₂

   https://doi.org/10.1002/ejic.202000518  

   Smith Pellizzeri, Tiffany M.; Morrison, Gregory; McMillen, Colin D.; zur Loye, Hans‐Conrad; Kolis, Joseph W. (September 2020, European Journal of Inorganic Chemistry)

   null (Ed.)