X-ray photoelectron,emission, and absorption studies of the electronic structure of molybdenum and tungsten trisulfides and their intercalates

The electronic structure of molybdenum and tungsten trisulfides and their lithium intercalates is investigated by X-ray emission, absorption, and photoelectron spectroscopy. The electron density of lithium atoms intercalated into molybdenum and tungsten trisulfides is distributed over both the metal and sulfur atoms, with more over the atoms of the disulfide pair. These compounds are assumed to have an additional donor-acceptor bond involving a lone pair of disulfide sulfur atom electrons and the vacant levels of the metal. A qualitative scheme of the electronic structure of MoS₃ is constructed based on experimental results and assuming the presence of a donor-acceptor bond. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 6, pp. 81–93, November–December, 1994. Translated by L. Smolina     

X-ray emission and X-ray photoelectron study of the electronic structure of polymeric cubanocluster compounds Re4−x Mo x S4Te4

The electronic structure of cubanocluster compounds of the series Re_4−xMo_xS₄Te₄ was studied by X-ray emission and X-ray photoelectron spectroscopy. The electronic structure of the (Re₄S₄)⁸⁺ cluster was calculated by the EHT method. It is shown that replacement of rhenium atoms by molybdenum atoms leads to changes both in the chemical bonds of the Re₄S₄ cubanocluster fragment and in the bond of the latter with the Te₄ fragment. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 901–906, September–October, 1996. Translated by L. Smolina     

X-ray emission and X-ray photoelectron studies of the electronic structure of the polymeric cubane cluster compounds Mo4S4Cl4, GaMo4S8, and GaMo4S4Te4

X-ray emission and X-ray photoelectron spectroscopy was used to study the electronic structures of the polymeric cubane cluster compounds Mo₄S₄Cl₄, GaMo₄S₈, and GaMo₄S₄Te₄. It is revealed that the ligand orbitals make significant contributions to the highest occupied molecular orbitals (M−M bonds). Substitution in the series Cl−S−Te increases the covalence of the metal—bridging ligand bonds. The experimental spectra allowed the construction of a qualitative scheme of the electronic structure of Mo₄S₄Cl₄. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 1038–1045, November–December, 1995. Translated by I. Izvekova     

Structure and lithium mobility of Li<Subscript>4</Subscript>Pt<Subscript>3</Subscript>Si

The lithium-rich silicide Li₄Pt₃Si was synthesised from the elements by high-temperature synthesis in a sealed niobium ampoule. Its structure was refined on the basis of single-crystal X-ray diffraction data: R32, a = 693.7(2), c = 1627.1(4) pm, wR2 = 0.0762, 525 F² values and 21 variables. The striking structural motifs of the Li₄Pt₃Si structure are silicon atoms with a slightly distorted trigonal prismatic platinum coordination with short Si–Pt distances (238–246 pm). Always two trigonal prisms are condensed via a common Pt₃ triangle, and these double units built up a three-dimensional network by condensation via common corners. The channels left by this prismatic network are filled by two crystallographically independent lithium sites in a 3:1 ratio. The single crystal X-ray data were fully confirmed by neutron powder diffraction and ⁷Li magic-angle spinning (MAS)–nuclear magnetic resonance (NMR) results. The two distinct lithium sites are well differentiated by their ⁷Li isotropic chemical shift and nuclear electric quadrupolar interaction parameters. MAS-NMR spectra reveal signal coalescence effects above 300 K, indicating chemical exchange between the lithium sites on the millisecond timescale. The spectra can be simulated with a simple two-site exchange model. From the resulting temperature-dependent correlation times, an activation energy of 50 kJ/mol is extracted.     

Crystallochemical features of the anion varieties of aluminum and lithium binary hydroxide

Crystallochemical features of anion (Cl⁻, Br⁻, I⁻, NO ₃ ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ ) varieties of the aluminum and lithium hydroxide were studied by using the aluminum and lithium binary hydroxide (LiOH·2Al(OH)₃·2H₂O) model in space group P6₃cm with the tetrahedral coordination of lithium. Atomic coordinates corresponding to the lowered lattice symmetry were refined. Institute of Solid State Chemistry and Processing of Mineral Raw Materials, Siberian Branch, Russian Academy of Sciences. Novosibirsk State Pedagogical University. Translated fromZhurnal Struktumoi Khimii, Vol. 35, No. 5, pp. 158–170, September–October, 1994. Translated by T. Yudanova     

花瓣状微球MoS2/石墨烯复合材料的制备及其电化学性能

采用有利于二维层状结构形成的L-半胱氨酸作为硫源,钼酸钠作为钼源,制备聚乙烯基吡咯烷酮（PVP）辅助水热合成花瓣状微球形貌的MoS₂/还原氧化石墨烯复合电极材料（PVP-MoS₂/RGO）. X射线衍射（XRD）及透射电子显微镜（TEM）证实,经过PVP的适量添加,MoS₂有序堆垛结构的片层数目明显减少. 扫描电子显微镜（SEM）显示,添加适量PVP的MoS₂/石墨烯材料具有分散性更好的花瓣状微球形貌. 上述的少层有序堆垛结构及复合材料的良好分散性缩短了MoS₂中锂离子的嵌入/脱出路径,使其具有更高的容量、循环稳定性和倍率性能.     

Electronic structure and spectral characteristics of Bi-Sr-Ca-Cu-O films

The electronic structure of high-temperature superconducting films of Bi-Sr-Ca-Cu-O is determined using the linearized augmented plane wave method. Total and local partial densities of states are calculated for each film using the results of band structure calculations. Theoretical OK_α and CuL_α X-ray emission spectra are found. The dependence of the electronic structure and spectra on the number of CuO₂ layers in the unit cell is discussed. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 6, pp. 1067–1075, November–December, 1998.     

X-ray photoelectron study of the state of Ba atoms in YBa2Cu3O7−δ doped with Co and Zn atoms

Investigating changes in the charged state of atoms upon superconductivity-suppressing substitutions is one of the methods to examine a relationship between the electronic structure of HTSC materials and the transition temperature to the superconducting state. In this paper, we measured E_bnd of the inner levels of Ba atoms in Co- and Zn-doped YBa₂Cu₃O_7−δ by X-ray photoelectron spectroscopy. Upon copper substitution by Co and Zn atoms, E_bnd of the inner levels diminishes for Ba atoms but remains the same for Cu and O atoms. The change of E_bnd of the inner levels of Ba atoms is attributed to the change of the Fermi level position in the “anionic” sublattice of (Cu₃O_7−δ)⁷⁻. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 4, pp. 91–95, July–August, 1994. Translated by L. Smolina     

Effect of the ZnNi y Mn2– y O4 (0 ≤ y ≤ 1) spinel composition on electrochemical lithium insertion

The electrochemical insertion of lithium in the spinel-type manganite with the formula ZnNi _y Mn_{2– y} O₄ has been studied. The galvanostatic discharge curves show that the best performance is obtained for y = 0.25, where a tetragonal to cubic structural transformation occurs. The thermodynamics and kinetics of the process of insertion of the lithium into the tetragonal spinel Li _x ZnNi_0.25Mn_1.75O₄ (x = 0.05–1.3) have been studied. The molar thermodynamic quantities, such as enthalpy, entropy and free energy determined by EMF-T measurements, varied with the lithium concentration in the oxide structure, and a major variation was observed around x = 0.8. The chemical diffusion coefficient of lithium in these spinels was also determined. Structural analysis, degree of oxidation and magnetic susceptibility measurements were carried out for the lithiated oxides in order to obtain the cationic distribution as a function of x. It has been possible to demonstrate that, upon lithium insertion, Mn⁴⁺ ions on B sites are reduced to Mn³⁺ and then to Mn²⁺. A cooperative Jahn-Teller effect is present in these spinel manganese-nickel oxides. Received: 4 February 1997 / Accepted: 11 April 1997     

Comparative study of the electronic structure of Bi-Systems 2212

The electronic structure of conducting and nonconducting forms of Bi₂Sr₂CaCu₂O_8+x ceramics was investigated by X-ray and X-ray photoelectron spectroscopy. The conducting form differs in structure from the nonconducting one by the presence of oxygen and bismuth atoms in two oxidation states as well as by pd-hybridization of O2p- and Cu3d-electrons in the valence band. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhumal Struktumoi Khimii, Vol. 36, No. 1, pp. 108–111, January–February, 1995. Translated by L. Smolina     

Joint X-ray spectroscopic and quantum-chemical study of the electronic structure of pentafluorophenylalkyl ethers

The high resolution X-ray emission O-Kα spectra of pentafluorophenylalkyl ethers C₆F₅OR (R=Et, Prⁱ, and Bu^t) exhibit differences related to a change in the electronic structure of the compounds as R is varied. The search for stable conformers was performed by the semiempirical PM3 method. The most probable structures of C₆F₅OR were determined by the comparison of the experimental and theoretical X-ray spectra plotted for each conformer usingab initio calculations in the 6–31 G basis set. Substituent R in pentafluorophenylalkyl ethers is situated outside of the ring plane. The fluorination of the benzene ring changes the energy level of the lone electron pair of oxygen relative to the levels of orbitals of the ring and substituent R and leads to an increase in the efficiency of interactions in the σ-system. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2443–2450, December, 1998.     

Electronic structure and spin bonds in the [(NH3)5Cr-O-Cr(NH3)5]4+ complex

The electronic structure of the lowest singlet, triplet, quintet, and septet states of the binuclear complex [Cr(NH₃)₅]₂O⁴⁺ are calculated by the semiempirical MC SCF method in the INDO approximation. Schemes of spin coupling of Cr-O-Cr in these states are analyzed. Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 3, pp. 457–464, May–June, 1997.     

X-ray Photoelectron Spectroscopy and Time-Of-Flight Secondary Ion Mass Spectroscopy studies of electrodeposited molybdenum oxysulfide cathodes for lithium and lithium-ion microbatteries

Thin-film molybdenum oxysulfide cathodes for lithium and lithium–ion microbatteries were fabricated by a simple electrodeposition method. According to Scanning Electron Microscopy (SEM) data, the deposition parameters affect the morphology of the cathodes. X-ray diffraction (XRD) tests indicated that the sub-micron-thick molybdenum oxysulfide films are amorphous or form too small crystallites to give rise to detectable X-ray diffraction peaks. A variety of poly-ion clusters containing both oxygen and sulfur (like MoOS, MoO₂S and MoS₂O and others) detected by TOF-SIMS tests unambiguously indicates the formation of molybdenum oxysulfide compounds, and not a mixture of oxides and sulfides, during electrodeposition. The sulfur-to-oxygen ratio in the bulk of the deposit is about 1.76 and does not depend much on the electrodeposition parameters. XPS studies reveal that electrodeposition in unbuffered solutions produces deposits with high oxygen and low sulfur content, as compared with cathodes deposited in buffered solutions. Potentiostatic, as compared to galvanostatic deposition, is followed by the formation of cathode films with slightly higher sulfur and lower oxygen content at the same pH. An increase in the pH of electrolyte solutions from 8 to 9.5 slightly reduces sulfur content, but appreciably increases oxygen concentration. Charge–discharge overpotential of Li/hybrid polymer electrolyte microbatteries is lower in sulfur-rich MoO_xS_y cathodes.     

Synthesis and solid state characterization of two insoluble tetrathiometalates

The aqueous reaction of ammonium tetrathiometalates (NH₄)₂[MS₄] (M = Mo or W) with (dbtmen)Br₂ · 2H₂O (dbtmen = N,N′-dibenzyl-N,N,N ′, N′-tetramethylethylenediammonium dication) results in the formation of the highly insoluble compounds (dbtmen)[MoS₄] (1) and (dbtmen)[WS₄] (2) in near quantitative yields. Compounds (1) and (2) have been characterized by elemental analysis, spectroscopic methods, X-ray powder diffraction and TG–DTA. Both compounds exhibit nearly identical IR spectra and X-ray powder patterns. The compounds exhibit a single strong signal for the asymmetric M–S stretching vibration at 475 cm⁻¹ in (1) and at 457 cm⁻¹ in (2). Complex (2) is thermally more stable than the corresponding Mo analogue (1). Thermal decomposition products of (1) and (2) are carbon contaminated amorphous metal disulfides and are formulated as MoS_1.99C_2.06N_0.07 and WS_1.75C_3.02 based on elemental analysis of the residue.     

X-ray spectra and electronic structure of solid ammonia

Intermolecular interactions in solid ammonia are investigated in a combined X-ray spectral and quantum chemical study. Theoretical NK_α spectra are constructed on the basis of MNDO calculations of the ammonia molecule and (NH₃)₇ and (NH₃)₁₃ clusters modeling solid ammonia; the spectra are in satisfactory agreement with the experimental X-ray spectra. Fragment analysis of the clusters with respect to the central ammonia molecule is carried out. It is shown that intermolecular electronic interactions in solid ammonia are most effective in MOs of e symmetry (σ-binding of nitrogen and hydrogen atoms). The fragment 2a₁ orbital contributes to the MO structure of the clusters to the least extent. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 4, pp. 721–726, July–August, 1996. Translated by L. Smolina     

Electronic structure and properties of the ground state of copper in semiconducting cuprates

The spin-polarized discrete variational X_a method is used to calculate clusters that model the electronic structures of CuO, La₂CuO₄, and Nd₂CuO₄. It, is shown that in each of the compounds the unoccupied portion of the valence band involves mainly the O2p states, the contributions from the Cu3d orbitals being significantly smaller. The effects of the nature of holes in the valence band and of the structure of the close environment of copper on the low-energy CuK spectra and the X-ray photoelectron spectra of the above systems are discussed. Institute of Solid State Chemistry, Ural Branch, Russian Academy of Sciences. Translated fromZhumal Struktumoi Khimii, Vol. 36, No. 4, pp. 636–643, July–August., 1995. Translated by I. Izvekova     

Geometry of the oxygen environment of molybdenum in NiMoO4 crystals

XANES and EXAFS data for molybdenum in NiMoO₄, Na₂MoO₄(2H₂O), and MoO₃ crystals are reported. Analysis of this information and the results of numerical simulations suggest the octahedral oxygen environment of molybdenum in NiMoO₄. Institute of Solid State Chemistry and Processing of Minerals, Siberian Branch, Russian Academy of Sciences. Institute of Catalysis, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 6, pp. 998–1003, November–December, 1995. Translated by I. Izvekova     

X-ray spectra and electronic energy structure of carboaluminides Ti-Al-C

The electronic energy structure, TiL_2,3 X-ray emission, and TiL2j XANES spectra of diamond and titanium carboaluminides Ti-Al-C are calculated by the local coherent potential method in terms of multiple scattering theory. The cluster version of the MT approximation is used to calculate the crystal potential. The electronic energy structures of diamond and the ternary and binary titanium carbide systems are compared in a single approximation. The broadening of the hybridized band in Ti-Al-C is discussed and compared with the experimental CK_α emission spectra. The specifics of chemical binding in the compounds is explained by delocalization of the carbon sp³ configuration and formation of a metal bond in carboaluminides. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 3, pp. 505-514, May–June, 2000.     

Intercalation of molybdenum disulfide with chlorobis(phenanthroline)copper(II)

An intercalation compound of molybdenum disulfide with the copper complex Cu^II(phen)₂Cl⁺ was found to form by the interaction of the MoS₂ single-layer dispersions with the complex and by the treatment of the phenanthroline intercalation compound with CuCl₂. The compositions and structures of the compounds formed were determined by powder diffractometry and electron microscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2648–2654, December, 2005.     

X-ray and quantum chemical study of the electronic structure of glycine and its metal complexes

OK_α spectra of glycine and some transition metal complexes with glycine ligands were obtained. The electronic structure of the glycine zwitterion is calculated by a quantum chemical method, and a theoretical X-ray spectrum of the glycine molecule is constructed. The nature of the metal-ligand bond in the compounds is discussed on the basis of experimental spectra and theoretical calculations. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Moscow State Academy of Light Industry, Novosibirsk Branch. Moscow State Academy of Light Industry. Novosibirsk State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 112–116, July–August, 1994. Translated by L. Smolina