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1. The proof is in the powder: revealing structural peculiarities in the Yb ₃ Rh ₄ Sn ₁₃ structure type

   https://doi.org/10.1039/C7CE00419B  

   Oswald, Iain W.; Rai, Binod K.; McCandless, Gregory T.; Morosan, Emilia; Chan, Julia Y. (January 2017, CrystEngComm)
2. The role of Co valence in charge transport in the entropy‐stabilized oxide (Mg _0.2 Co _0.2 Ni _0.2 Cu _0.2 Zn _0.2 )O

   https://doi.org/10.1111/jace.18820  

   Jacobson, V.; Huang, J.; Titus, C. J.; Smaha, R. W.; Papac, M.; Lee, S. J.; Zakutayev, A.; Brennecka, G. L. (October 2022, Journal of the American Ceramic Society)

   Abstract Many of the studies on the entropy‐stabilized oxide (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O have been heavily application‐based. Previous works have studied effects of cation stoichiometry on the entropy‐driven reaction to form a single phase, but a fundamental exploration of the effects of anion stoichiometry and/or redox chemistry on electrical properties is lacking. Using near‐edge X‐ray absorption fine structure (NEXAFS) and electrical measurements, we show that oxidizing thin film samples of (Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O affects primarily the valence of Co, leaving the other cations in this high‐entropy system unchanged. This oxidation increases electrical conduction in these thin films, which occurs via small polaron hopping mediated by the Co valence shift from 2+ to a mixed 2+/3+ state. In parallel, we show that bulk samples sintered in an oxygen‐rich atmosphere have a lower activation energy for electrical conduction than those equilibrated in a nitrogen (reducing) atmosphere. Combining feasible defect compensation scenarios with electrical impedance measurements and NEXAFS data, we propose a self‐consistent interpretation of Co redox‐mediated small polaron conduction as the dominant method of charge transfer in this system. 

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3. Emergent properties in the natural composite Ni ₂ MnSb _0.5 Al _0.5

   https://doi.org/10.1088/1361-6463/ab7c9f  

   Samanta, Tamalika; Salas, D; Srihari, V; Karaman, I; Bhobe, P A (May 2020, Journal of Physics D: Applied Physics)
4. A quantum dynamical study of the rotation of the dihydrogen ligand in the Fe(H) ₂ (H ₂ )(PEtPh ₂ ) ₃ coordination complex

   https://doi.org/10.1063/1.5026637  

   Gonzalez, Megan E.; Eckert, Juergen; Aquino, Adelia J.; Poirier, Bill (April 2018, The Journal of Chemical Physics)
5. Nonadiabatic coupling of the dynamical structure to the superconductivity in YSr ₂ Cu _2.75 Mo _0.25 O _7.54 and Sr ₂ CuO _3.3

   https://doi.org/10.1073/pnas.2018336117  

   Conradson, Steven D.; Geballe, Theodore H.; Jin, Chang-Qing; Cao, Li-Peng; Gauzzi, Andrea; Karppinen, Maarit; Baldinozzi, Gianguido; Li, Wen-Min; Gilioli, Edmondo; Jiang, Jack M.; et al (December 2020, Proceedings of the National Academy of Sciences)

   null (Ed.)

   A crucial issue in cuprates is the extent and mechanism of the coupling of the lattice to the electrons and the superconductivity. Here we report Cu K edge extended X-ray absorption fine structure measurements elucidating the internal quantum tunneling polaron (iqtp) component of the dynamical structure in two heavily overdoped superconducting cuprate compounds, tetragonal YSr 2 Cu 2.75 Mo 0.25 O 7.54 with superconducting critical temperature, T c = 84 K and hole density p = 0.3 to 0.5 per planar Cu, and the tetragonal phase of Sr 2 CuO 3.3 with T c = 95 K and p = 0.6. In YSr 2 Cu 2.75 Mo 0.25 O 7.54 changes in the Cu-apical O two-site distribution reflect a sequential renormalization of the double-well potential of this site beginning at T c , with the energy difference between the two minima increasing by ∼6 meV between T c and 52 K. Sr 2 CuO 3.3 undergoes a radically larger transformation at T c , >1-Å displacements of the apical O atoms. The principal feature of the dynamical structure underlying these transformations is the strongly anharmonic oscillation of the apical O atoms in a double-well potential that results in the observation of two distinct O sites whose Cu–O distances indicate different bonding modes and valence-charge distributions. The coupling of the superconductivity to the iqtp that originates in this nonadiabatic coupling between the electrons and lattice demonstrates an important role for the dynamical structure whereby pairing occurs even in a system where displacements of the atoms that are part of the transition are sufficiently large to alter the Fermi surface. The synchronization and dynamic coherence of the iqtps resulting from the strong interactions within a crystal would be expected to influence this process. 

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