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Acta Cryst. (2014). A70, C861
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Transition metal-metalloid amorphous systems such as Fe-B and Ni-B are usually applied for the soft magnetic metallic glassy alloys and are counted as one of prominent categories in the field of amorphous alloy technology. Since glass forming ability of these systems correlates closely with the atomic level structure depending on chemical species of metal and metalloid, the local structure analysis for these glassy alloys is strongly required. In order to obtain the reliable structural model for these metal (Fe, Ni)-metalloid (B) amorphous samples, we determined the partial structural functions by combinational use of neutron diffraction (ND) and anomalous X-ray scattering (AXS). The amorphous ribbon samples were produced by the single-roller melt-spinning technique. The AXS measurements at Fe and Ni absorption edges were carried out at BL-7C of Photon Factory, KEK. The ND experiment was performed by using the time-of-flight technique and high intensity total diffractometer, NOVA at MLF, J-PARC. The figure shows the g(r)s for Fe80B20, Ni81B19, and Ni60B40 calculated by the interference functions obtained by ND measurements. The dashed lines in the figure indicate the interatomic distances estimated from Goldschmidt atomic radii (Fe: 1.28 Å, Ni: 1.25 Å, B: 0.97 Å). At the nearest neighbor region up to about 3 Å, the first peak could be accounted for a harmony of metal (M)-B and B-B pair correlations and the second peak is mainly contributed by the M-M pair correlation. As for the three dimensional structural modeling of the amorphous samples, reverse Monte Carlo simulation has been performed starting from an initial model of 2,000 atoms with the b.c.c. structure. The present simulation results are found to reproduce the experimental interference functions obtained by the ND, ordinary X-ray diffraction, and AXS measurements. We will present the obtained structural model and local structural units around B including their arrangement.




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Acta Cryst. (2014). A70, C1111
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Kottogite and symplesite are zinc and ferrous arsenate minerals, respectively. These minerals make the Zn3-x,Fex(AsO4)2·8H2O solid-solution and belongs to the vivianite group of minerals with the chemical formula M3(TO4)2·8H2O. The structure of vivianite and symplesite were determined firstly by Mori and Ito, (1950). The structure of kottigite was refined by Hill, (1979). The strucrure of Zn1.63Fe1.37(AsO4)2·8H2O solid-solution crystallize in space group C2/m with a= 10.342(1), b= 13.484(2), c= 4.7756(5), [beta]=105. 306(4), and Z=2. We performed the structure refinements of (Zn,Fe)3(AsO4)2·8H2O solid-solutions, Ojuela mine, Mapimi Durango, Mexico and Kiura mine, Ohita, Japan by RIGAKU single-crystal structure analysis system RAPID. The R and S values are around 0.03 and 1.08. We determined detail atomic coordinate and hydrogen atom positions. The hydrogen bonds were revealed based on hydrogen positions and bond valence caluculations. The octahedral edge-shareing M2O6(H2O)4 dimers and insular MO2(H2O)4 octahedra are linked by AsO4 terahedra. Two H2O group bonds to (Zn,Fe). Four hydrogen atoms are in the normal hydrogen bonds. Hydrogen atom positions have a tunnel structure and there is a path of proton-conduction and we conjecture that proton conductivity has large anisotropy of one direction. The related minerals, such as paradamite, legrandite and warikahnite have tunnel structure similar to vivianite group.

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Acta Cryst. (2008). A64, C605
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Acta Cryst. (2011). A67, C697
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Single crystals of LaAlO3 (lanthanum aluminium trioxide) have been synthesized at 4.5 GPa and 1273 K, in the presence of an NaCl + KCl flux. The compound crystallizes with the cubic perovskite structure (space group Pm\overline{3}m). The thermal vibration of the O atom is remarkably suppressed in the directions of the Al-O bonds, and this anisotropy ranks among the largest observed in stoichiometric cubic perovskites.

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The crystal structure of the low-temperature (LT) modification of LaBO3 has been redetermined from single-crystal X-ray data; the resulting structure confirms the previous study [Abdullaev, Dzhafarov & Mamedov (1976). Azerbaidzhanskii Khim. Zh. pp. 117–120], but with improved precision. LT-LaBO3 crystallizes in space group Pnma and adopts the aragonite-type structure. Except for one O atom, which is situated on a general position, all other atoms (one La, one B and a second O atom) lie on mirror planes. The structure is composed of LaO9 polyhedra with an average La—O distance of 2.593 Å and trigonal BO3 groups with an average B—O distance of 1.373 Å. Slight anisotropies of the thermal vibrations of La and B atoms suggest that the electrostatic La...La and La...B inter­actions across the shared edges are weak.

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The high-pressure phase of SrGeO3 synthesized at 6 GPa and 1223 K adopts the ideal cubic perovskite-type structure. The Ge-O bond is largely covalent, which influences the thermal vibration behavior of the O atom.

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Acta Cryst. (2014). A70, C1457
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The pyrochlore-type iridium oxide Eu2Ir2O7 exhibits a metal-insulator transition at 120 K, accompanied by magnetic ordering. We performed resonant x-ray scattering (RXS) experiment with photon energies near the iridium absorption edge L3 to investigate the arrangement of Ir4+ magnetic moments. Magnetic RXS was observed in the insulating phase, providing direct evidence of long-range ordering of Ir4+ magnetic moments with a propagation vector of (4n+2 0 0) . Our single-crystal structure analysis revealed that the lattice retains its face-centered-cubic structure across the metal-insulator transition, indicating all-in-all-out magnetic order, where all the magnetic moments on the four vertices of each Ir4+ tetrahedron point inward or outward as shown in Fig. 1 [1]. To investigate the 5d-electronic state of Ir4+, we performed resonant inelastic x-ray scattering (RIXS) experiment near the L3 edge. Obtained RIXS spectra indicate that the 5d-electronic state is affected by not only the spin-orbit interaction but also trigonal distortion of IrO6 octahedron [2].



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Acta Cryst. (2017). A73, C625
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Acta Cryst. (2017). A73, C989
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Acta Cryst. (2008). A64, C67
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Acta Cryst. (2008). A64, C524
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