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1. Temperature Dependence of the Indirect Gap and the Direct Optical Transitions at the High-Symmetry Point of the Brillouin Zone and Band Nesting in MoS ₂ , MoSe ₂ , MoTe ₂ , WS ₂ , and WSe ₂ Crystals

   https://doi.org/10.1021/acs.jpcc.2c01044  

   Kopaczek, J.; Zelewski, S.; Yumigeta, K.; Sailus, R.; Tongay, S.; Kudrawiec, R. (March 2022, The Journal of Physical Chemistry C)
2. 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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3. Energetics and structure of the B‐type solid solution in the Nd ₂ O ₃ –Y ₂ O ₃ system

   https://doi.org/10.1111/jace.18522  

   Mandia, Ramandeep; Navrotsky, Alexandra (September 2022, Journal of the American Ceramic Society)
4. It Runs in the BaAl ₄ Family: Relating the Structure and Properties of Middle Child Ln ₂ Co ₃ Ge ₅ (Ln = Pr, Nd, and Sm) to its Siblings LnCo ₂ Ge ₂ and LnCoGe ₃

   https://doi.org/10.1021/acs.inorgchem.1c01978  

   Kyrk, Trent M.; Scheifers, Jan P.; Thanabalasingam, Kulatheepan; McCandless, Gregory T.; Young, David P.; Chan, Julia Y. (October 2021, Inorganic Chemistry)
5. The crystal and defect structures of polar KBiNb ₂ O ₇

   https://doi.org/10.1039/d1dt04064b  

   Mallick, Subhadip; Zhang, Weiguo; Batuk, Maria; Gibbs, Alexandra S.; Hadermann, Joke; Halasyamani, P. Shiv; Hayward, Michael A. (February 2022, Dalton Transactions)

   KBiNb 2 O 7 was prepared from RbBiNb 2 O 7 by a sequence of cation exchange reactions which first convert RbBiNb 2 O 7 to LiBiNb 2 O 7 , before KBiNb 2 O 7 is formed by a further K-for-Li cation exchange. A combination of neutron, synchrotron X-ray and electron diffraction data reveal that KBiNb 2 O 7 adopts a polar, layered, perovskite structure (space group A 11 m ) in which the BiNb 2 O 7 layers are stacked in a (0, ½, z ) arrangement, with the K + cations located in half of the available 10-coordinate interlayer cation sites. The inversion symmetry of the phase is broken by a large displacement of the Bi 3+ cations parallel to the y -axis. HAADF-STEM images reveal that KBiNb 2 O 7 exhibits frequent stacking faults which convert the (0, ½, z ) layer stacking to (½, 0, z ) stacking and vice versa , essentially switching the x - and y -axes of the material. By fitting the complex diffraction peak shape of the SXRD data collected from KBiNb 2 O 7 it is estimated that each layer has approximately a 9% chance of being defective – a high level which is attributed to the lack of cooperative NbO 6 tilting in the material, which limits the lattice strain associated with each fault. 

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