- Crystallographic, Electronic, and Magnetic Properties of Rock Salt Superstructure Sulfide Lu2CrS4 with Jahn-Teller Distortion
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A new chromium(II) sulfide, Lu2CrS4, with a novel structure was prepared by a solid-state reaction. The powder X-ray diffraction pattern could be indexed as a tetragonal system, with a = 7.46373(2) ?, c = 22.6338(2) ?, and space group I42d (No. 122). Rietveld analysis of the pattern provided the crystal structure consisting of CrS6 and LuS6 octahedra sharing edges and apexes and revealed a rock salt superstructure with new cation (vacancy) arrangements. The electrical resistivity indicates semiconducting behavior. The magnetic susceptibility and specific heat measurements showed that the Cr ions are in the high-spin d4 configuration and that their magnetic moments ordered antiferromagnetically at 55 K. The basic antiferromagnetic structure was determined using powder neutron diffraction data at 10 K. The band structure calculations demonstrate that the densities of states of Cr 3d electrons split into two spin-up eg bands because of Jahn-Teller distortion.
- Tezuka, Keitaro,Wakeshima, Makoto,Nozawa, Masataka,Oshikane, Keita,Ohoyama, Kenji,Shan, Yue Jin,Imoto, Hideo,Hinatsu, Yukio
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- Electronic structure of Cr1-δS (δ=0, 0.17) with NiAs-type crystal structure
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Valence-band and conduction-band the electronic structure of the CrS (δ=0) and Cr5S6 (δ=0.17) has been investigated by means of photoemission and inverse-photoemission spectroscopies. The bandwidth of the valence bands of Cr5S6 (8.5 eV) is wider than that of CrS (8.1 eV), though the Cr 3d partial density of states evaluated from the Cr 3p-3d resonant photoemission spectroscopy is almost unchanged between the two compounds concerning shapes as well as binding energies. The Cr 3d (t2g) exchange splitting energies of CrS and Cr5S6 are determined to be 3.9 and 3.3 eV, respectively.
- Koyama,Sato,Ueda,Hirai,Taniguchi
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- Simultaneous diffraction and resistance measurements of metal sulphides
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We describe the construction of a cell that enables the electrical resistance of a material to be measured simultaneously with the collection of powder neutron diffraction data at elevated temperatures. The cell has been used to investigate the origin of the anomalous electron-transport properties of the monosulphide, CrS. The data reveal that a decrease in electrical resistance above 573 K is associated with the disappearance of semiconducting monoclinic CrS and the concomitant growth of a disordered CdI2-type metallic phase.
- Powell, Anthony V.,Erinc Engin,Vaqueiro, Paz,Hull, Steve
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- Synthesis and characterization of 3-methyl-5-oxo-N,1-diphenyl-4,5-dihydro-1-H-pyrazole-4-carbothioamide and its metal complexes
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The molecular parameters have been calculated to confirm the geometry of 3-methyl-5-oxo-N,1-diphenyl-4,5-dihydro-1-H-pyrazole-4-carbothioamide, HL. The compound is introduced as a new chelating agent for complexation with Cr(III), Fe(III), Co(II), Ni(II) and Cu(II) ions. The isolated chelates were characterized by partial elemental analyses, magnetic moments, spectra (IR, UV-vis, ESR; 1H NMR) and thermal studies. The protonation constant of HL (5.04) and the stepwise stability constants of its Co(II), Cu(II), Cr(III) and Fe(III) complexes were calculated. The ligand coordinates as a monobasic bidentate through hydroxo and thiol groups in all complexes except Cr(III) which acts as a monobasic monodentate through the enolized carbonyl oxygen. Cr(III) and Fe(III) complexes measured normal magnetic moments; Cu(II) and Co(II) measured subnormal while Ni(II) complex is diamagnetic. The data confirm a high spin and low spin octahedral structures for the Fe(III) and Co(II) complexes. The ESR spectrum of the Cu(II) complex support the binuclear structure. The molecular parameters have also been calculated for the Cu(II) and Fe(III) complexes. The thermal decomposition stages of the complexes confirm the MS to be the residual part. Also, the thermodynamic and kinetic parameters were calculated for some decomposition steps.
- El-Shazly
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- Crystal and magnetic structures of Y2CrS4
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Chromium(II) sulfide, Y2CrS4, prepared by a solid-state reaction of Y2S3 and CrS, showed an antiferromagnetic transition at 65 K. The neutron diffraction patterns at 10 and 90 K were both well refined with the space group Pca21. At 90 K, cell parameters were a=12.5518(13) ?, b=7.5245(8) ?, and c=12.4918(13) ?. At 10 K, magnetic peaks were observed, which could be indexed on the same unit cell. Magnetic moments of chromium ions were parallel to the b-axis and antiferromagnetically ordered in each set of the 4a sites.
- Tezuka, Keitaro,Shan, Yue Jin,Imoto, Hideo,Ohoyama, Kenji
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- Microwave-assisted Solid-state Reactions involving Metal Powders
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The ability of metal powders to couple to microwave radiation at 2450 MHz has been used to accelerate a range of solid-state reactions.Although metal objects cause extensive arcing within a microwave cavity, metal powders couple in a more conventional manner with the microwave radiation and experience high heating rates.This property has been utilised for the synthesis of metal chalcogenides and metal cluster compounds of the Group 5 and 6 elements.
- Whittaker, A. Gavin,Mingos, D. Michael P.
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- Synthesis and anti-fungicidal activity of some transition metal complexes with benzimidazole dithiocarbamate ligand
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Seven transition metal complexes of benzimidazole ligand (HL) are reported and characterized based on elemental analyses, IR, solid reflectance, magnetic moment, molar conductance and thermal analyses (TGA and DTA). From the obtained data, the complexes w
- Mohamed, Gehad G.,Ibrahim, Nasser A.,Attia, Hanaa A.E.
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- High-temperature interactions of transition-metal carbides with Na2SO4
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The high-temperature (900-1200 K) interaction of transition-metal carbides namely Cr7C3, Fe3C, TiC, ZrC, NbC, TaC, MoC, WC, VC and HfC with Na2SO4 has been studied in a stream of pure and dried oxygen gas. Thermogravimetric studies were carried out by measuring the weight change as a function of time and mole fraction of Na2SO4 in the reaction mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were discussed on the basis of metallography, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The quantitative determination of soluble metal species in the aqueous solutions of Na2SO4-transition-metal carbide products was carried out by atomic absorption spectroscopy. At high temperatures, transition-metal carbides interact with Na2SO4, forming metal oxides. The resulting metal oxide interacts with Na2SO4 forming a soluble sodium metal oxide or a metal sulphide depending upon the local condition prevailing during the reaction.
- Mobin, M.,Malik, A. U.
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- New low-temperature synthesis of transition-metal sulfides
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The reaction of hexamethyldisilthiane with transition-metal halides at room temperature results in the rapid synthesis of transition-metal Sulfides. Sulfides that are normally difficult or even impossible to produce by using classical methods are readily produced. This method allows great control of reaction conditions and can be used with a wide range of transition metals and oxidation states. The sulfides that are synthesized are anhydrous, unlike those produced by many other low-temperature methods. This is a concern in applications such as the use of the materials as cathodes in secondary lithium batteries. The reactions were fast and usually exothermic, producing sulfides that were amorphous to X-ray diffraction. The only coproducts of the reaction between hexamethyldisilthiane and the metal halides are trimethylsilyl halides. These compounds are all volatile liquids and are easy to separate from the sulfides produced. Retention of the formal oxidation state of the metal from the halide was found in the sulfide in all cases.
- Martin, Michael J.,Qiang, Guo-Hua,Schleich, Donald M.
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p. 2804 - 2808
(2008/10/08)
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