Synthesis, Crystal Structure Refinement, and Electrical Conductivity of Pb(8−x)Na2Smx(VO4)6O(x/2)

Solid solutions of Pb(8−x)Na2Smx(VO4)6O(x/2) were studied using X-ray diffraction analysis including Rietveld refinement and scanning electron microscopy and by measuring their electrical conductivity. Crystal structure of the solid solutions was refined and the solubility region 0 ≤ x ≤ 0.2 was determined for samarium substitution for lead under the scheme 2Pb2+ + ◻ → 2Sm3+ + O2-. The influence of degree of substitution on the electrical conductivity of solid solutions was established

Hydrogen induced structural phase transformation in ScNiSn-based intermetallic hydride characterized by experimental and computational studies

Understanding an interrelation between the structure, chemical composition and hydrogenation properties of intermetallic hydrides is crucial for the improvement of their hydrogen storage performance. Ability to form the hydrides and to tune the thermodynamics and kinetics of their interaction with hydrogen is related to their chemical composition. Some features of the metal–hydrogen interactions remain however poorly studied, including chemistry of Sc-containing hydrides. ZrNiAl-type ScNiSn-based intermetallic hydride has been probed in the present work using a broad range of experimental techniques including Synchrotron and Neutron Powder Diffraction, $^{119}$Sn Möessbauer Spectroscopy, hydrogenation at pressures reaching several kbar H$_2$ and hydrogen Thermal Desorption Spectroscopy studies. Computational DFT calculations have been furthermore performed. This allowed to establish the mechanism of the phase-structural transformation and electronic structure changes causing a unique contraction of the metal lattice of intermetallic alloy and the formation of the ...H-Ni-H-Ni… chains in the structure with H atoms carrying a partial negative charge. Such hydrogen absorption accompanied by a formation of a covalent Ni-H bonding and causing an unusual behavior contracts to the conventionally observed bonding mechanism of hydrogen in metals as based on the metallic bonding frequently accompanied by a jumping diffusion movement of the inserted H atoms – in contrast to the directional Metal-Hydrogen bonding observed in the present work. At high applied pressures ScNiSnH$_{0.83}$ orthorhombic TiNiSi type hydride is formed with H atoms filling Sc$_3$Ni tetrahedra. Finally, this study shows that scandium closely resembles the behavior of the heavy rare earth metal holmium

CSD 1791492: Experimental Crystal Structure Determination

Related Article: Zoran Mazej, Evgeny Goreshnik, Zvonko Jaglicic, Yaroslav Filinchuk, Nikolay Tumanov, Lev G. Akselrud|2017|Eur.J.Inorg.Chem.||2130|doi:10.1002/ejic.20170005

Eine NiAs-artige Hochdruckmodifikation von FeN

Abstract Durch Kombination von Laser?geheizten Diamantstempelzellen mit Synchrotron?Mößbauer?Spektroskopie wurden die chemischen Hochtemperatur?Hochdruck?Reaktionen von Eisen und Eisennitrid, Fe2N, mit Stickstoff untersucht. Nach Erhitzen bei 1300?K bei Drücken über 10?GPa zeigte deutliche magnetische Hyperfeinaufspaltung die Bildung einer neuen Verbindung an. Anschließende röntgenographische In?situ?Analysen ergaben eine neue FeN?Modifikation im NiAs?Strukturtyp, deren Gesamtenergie und Bindungssituation über quantenchemische Methoden bestimmt wurden

Hydrogen induced structural phase transformation in ScNiSn-based intermetallic hydride characterized by experimental and computational studies

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Cluster Formation in the Superconducting Complex Intermetallic Compound Be₂₁Pt₅

ConspectusMaterials with the crystal structure of γ-brass type (Cu₅Zn₈ type) are typical representatives of intermetallic compounds. From the electronic point of view, they are often interpreted using the valence electron concentration approach of Hume–Rothery, developed previously for transition metals. The γ-brass-type phases of the main-group elements are rather rare. The intermetallic compound Be₂₁Pt₅, a new member of this family, was synthesized, and its crystal structure, chemical bonding, and physical properties were characterized.Be₂₁Pt₅ crystallizes in the cubic space group <i>F</i>4̅3<i>m</i> with lattice parameter <i>a</i> = 15.90417(3) Å and 416 atoms per unit cell. From the crystallographic point of view, the binary substance represents a special family of intermetallic compounds called complex metallic alloys (CMA). The crystal structure was solved by a combination of synchrotron and neutron powder diffraction data. Besides the large difference in the scattering power of the components, the structure solution was hampered by the systematic presence of very weak reflections mimicking wrong symmetry. The structural motif of Be₂₁Pt₅ is described as a 2 × 2 × 2 superstructure of the γ-brass structure (Cu₅Zn₈ type) or 6 × 6 × 6 superstructure of the simple bcc structural pattern with distinct distribution of defects. The main building elements of the crystal structure are four types of nested polyhedral units (clusters) with the compositions Be₂₂Pt₄ and Be₂₀Pt₆. Each cluster contains four shells (4 + 4 + 6 + 12 atoms). Clusters with different compositions reveal various occupation of the shells by platinum and beryllium. Polyhedral nested units with the same composition differ by the distance of the shell atoms to the cluster center.Analysis of chemical bonding was made applying the electron localizability approach, a quantum chemical technique operating in real space that is proven to be especially efficient for intermetallic compounds. Evaluations of the calculated electron density and electron localizability indicator (ELI-D) revealed multicenter bonding, being in accordance with the low valence electron count per atom in Be₂₁Pt₅. A new type of atomic interactions in intermetallic compounds, cluster bonds involving 8 or even 14 atoms, is found in the clusters with shorter distances between the shell atoms and the cluster centers. In the remaining clusters, four- and five-center bonds characterize the atomic interactions. Multicluster interactions within the polyhedral nested units and three-center polar intercluster bonds result in a three-dimensional framework resembling the structural pattern of NaCl. Be₂₁Pt₅ is a diamagnetic metal and one of rather rare CMA compounds revealing superconductivity (<i>T</i>_c = 2.06 K)