The structure of the compound Cd3P2

Structure of Cd₃P₂ (P4₂/nmc, a = b = 8.7390 Å, c = 12.2523 Å) has been solved and refined up to R = 3.78% using precision X-ray diffraction experimental data (λ-MoK _α, graphite monochromator on a primary beam, 11529 reflections). Interatomic distances and valence angles are determined. Phosphorus forms a face-centered cubic lattice in which 3/4 tetrahedral voids are occupied by cadmium atoms in the crystal structure. The structure can be described by two equivalent models in which the positions of cadmium atoms, which occupy tetrahedral voids following the “diamond principle,” are preserved, while the remaining free and occupied voids change their places.     

Structure and properties of Ce<Subscript>3</Subscript>Pd<Subscript>3</Subscript>Bi<Subscript>4</Subscript>, CePdBi,and CePd<Subscript>2</Subscript>Zn<Subscript>3</Subscript>

The intermetallic cerium compounds Ce₃-Pd₃Bi₄, CePdBi, and CePd₂Zn₃ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo₃B₂ type (ordered version of CaCu₅), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F ² values, 9 variables for CePd₂Zn₃ and Y₃Au₃Sb₄ type, I \({\bar 4}\)3d, a = 1005.2(2) pm, w R2 = 0.0402, 264 F ² values, 9 variables for Ce₃Pd₃Bi₄, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi₄ tetrahedra with Pd–Bi distances of 281 (Ce₃Pd₃Bi₄) and 296?pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce₃Pd₃Bi₄) and 10 (CePdBi). In CePd₂Zn₃ the cerium atoms fill larger channels within the three-dimensional [Pd₂Zn₃] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μ_eff = 2.70(2), 2.48(1), and 2.49(1) μ_B/Ce atom for CePd₂Zn₃, Ce₃Pd₃Bi₄, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1?K.     

Synthesis and crystal structure of new double mercury silver phosphide iodide Hg<Subscript>12</Subscript>Ag<Subscript>41</Subscript>P<Subscript>88</Subscript>I<Subscript>41</Subscript>

New double mercury silver phosphide iodide Hg₁₂Ag₄₁P₈₈I₄₁ (1) was synthesized and its crystal structure was established. Compound 1 crystallizes in the cubic system. The characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P₁₁ ³⁻, which have been previously found in alkali metal compounds only. The well-ordered P₁₁ ³⁻ clusters form a system of polyhedra, which encapsulate various disordered α-AgI-type fragments. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1882–1886, October, 2007.     

Interatomic interactions and electronic structure of NbSe<Subscript>2</Subscript> and Nb<Subscript>1.25</Subscript>Se<Subscript>2</Subscript> nanotubes

Atomic models of achiral NbSe₂ nanotubes are suggested. Band structure calculations have been performed to investigate the electronic structure and determine the parameters of interatomic interactions. The distribution of the density of states and pair bond occupancies of NbSe₂ nanotubes are analyzed in relation to the type of the atomic configuration and the tube diameter; the results are compared with the band structure of the 2H-NbSe₂ crystal. Calculations have been carried out on hypothetical superstoichiometric nanotubes with a formal composition Nb_1.25Se₂ as possible quasi-one-dimensional nanoforms of autointercalated niobium diselenide.Original Russian Text Copyright © 2004 by A. N. Enyashin, V. V. Ivanovskaya, I. R. Shein, Yu. N. Makurin, N. I. Medvedeva, A. A. Sofronov, and A. L. IvanovskiiTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 579–588, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Structure and properties of Li<Subscript>2</Subscript>Zn<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> crystals activated with copper and chromium ions

Based on the corrected phase diagrams proper growth conditions for Li2Zn2(MoO₄)₃ crystals are selected. Large crystals (up to 100 mm), both impurity-free and activated by transition metal ions (Cu, Cr), are grown by the low-gradient Czochralski method. By the EPR method the charge state and structural position of copper and chromium ions are determined. The performed studies of luminescent properties show that for impurity-free crystals luminescence with λ = 388 nm with a two-exponential luminescence decay with τ₁ = 2 ns and τ₂ = 6 ns is observed at room temperature. At 77 K for both impurity-free crystals and those activated with transition metal ions luminescence with λ = 560 nm and the luminescence lifetime τ = 100 ns is observed, the intensity of luminescence with λ = 560 nm depending on the nature and concentration of transition metal ions. Cation vacancies responsible for the charge compensation of impurity transition metal ions are assumed to be also responsible for low-temperature luminescence.     

Comparing the electrochemical properties of pure phase Zn<Subscript>2</Subscript>SnO<Subscript>4</Subscript> and composite Zn<Subscript>2</Subscript>SnO<Subscript>4</Subscript>/C

Compound Zn₂SnO₄ was synthesized by a hydrothermal method in which SnCl₄ · 5H₂O, ZnCl₂ and N₂H₄ · H₂O were used as reactants. Composite Zn₂SnO₄/C was then synthesized through a carbothermic reduction process using the as-prepared Zn₂SnO₄ and glucose as reactants. Comparing to the pure Zn₂SnO₄, some improved electrochemical properties were obtained for composite Zn₂SnO₄/C. When doped with 15% glucose, the composite Zn₂SnO₄/C showed the best electrochemical performance. Its first discharge capacity was about 1500 mA h g⁻¹, with a capacity retain of 500 mA h g⁻¹ in the 40th cycle at a constant current density of 100 mA/g in the voltage range of 0.05–3.0 V. There were also some differences displayed in their cyclic voltammogram.     

Crystal structures of Ti(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript> and Sn(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>P<Subscript>4</Subscript>O<Subscript>13</Subscript>

The characteristics of crystal structures of the titanium(IV) diammonium (Ti(NH₄)₂P₄O₁₃) and tin(IV) diammonium (Sn(NH₄)₂P₄O₁₃) tetraphosphates, which are isostructural with similar silicon(IV) and germanium(IV) salts, have been obtained by the Rietveld method using X-ray powder diffraction data. The compounds crystallize in the triclinic system, space group P \(\overline 1 \), Z = 2, a = 15.0291(7) Å, b = 7.9236(4) Å, c = 5.0754(3) Å, α = 99.168(3)°, β = 97.059(3)°, γ = 83.459(3)° for Ti(NH₄)₂P₄O₁₃ and a = 15.1454(7) Å, b = 8.0103(5) Å, c = 5.1053(3) Å, α = 99.898(6)°, β = 96.806(3)°, γ = 83.881(4)° for Sn(NH₄)₂P₄O₁₃. The structure is refined in the isotropic approximation using the pseudo-Voigt function: R _p = 0.077, R _Bragg = 0.045, R _F = 0.057 for Ti(NH₄)₂P₄O₁₃; R _p = 0.082, R _Bragg = 0.044, R _F = 0.046 for Sn(NH₄)₂P₄O₁₃. The hydrogen atoms of the ammonium cations are placed in the calculated positions. A comparative analysis of the structures of the compounds of the M^IV(NH₄)₂P₄O₁₃ (M^IV = Si, Ge, Ti, Sn) series has been carried out.     

Synthesis and X-ray investigation of Rb<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>] and Cs<Subscript>2</Subscript>[Pd(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>]

Powder and single crystal X-ray diffraction studies have been performed for anhydrous nitrate complexes Rb₂[Pd(NO₃)₄] (I) and Cs₂[Pd(NO₃)₄] (II). Crystal data for I: a = 7.843(1) Å, b = 7.970(1) Å, c = 9.725(1) Å; β = 100.39(1)°, V = 597.9(1) Å ³, space group P2₁/c, Z = 2, d _calc = 2.918 g/cm³; for II: a = 10.309(2) Å, b = 10.426(2) Å, c = 11.839(2) Å; β = 108.17(3)°, V = 1209.0(4) ų, space group P2₁/c, Z = 4, d ^calc = 3.408 g/cm³. The structures are formed by isolated [Pd(NO₃)₄]^2? complex anions and alkali metal cations. The plane-square environment of the Pd atom is formed from the oxygen atoms of the monodentate nitrate groups. The geometrical characteristics of the complex anions are analyzed. Compound II has a short contact Pd...Cs 3.252 Å.     

Coordination Chemistry of the Magic Inorganic Building Block {Fe<Superscript>II</Superscript>[Mo<Subscript>6</Subscript>P<Subscript>4</Subscript>O<Subscript>31</Subscript>]<Subscript>2</Subscript>}: Hydrothermal Synthesis and Crystal Structure of a New Reduced Ferrous Molybdophosphate

A new reduced ferrous molybdophosphate composite solid of the formula, [(C₁₀H₁₄N₂)H]₄[Fe^II ₁₀Mo^V ₂₄(H₂PO₄)₄(HPO₄)₁₂(PO₄)₄(H₂O)₁₆(OH)₁₆O₄₄]·12H₂O, has been synthesized from a reaction mixture of MoO₃, FeSO₄·7H₂O, C₂H₂O₄·2H₂O, nicotine, H₃PO₄, and H₂O under hydrothermal conditions. The crystal data: monoclinic, space group C2/m, a = 24.4349(124), b = 12.9935(66), c = 14.7281(74) Å, β = 104.87(1) Å, V = 4520(4) Å³, Z = 2, R ₁  = 0.0874, wR ₂  = 0.2179. The structure is built from the building blocks of the formula, {Fe^II[Mo₆P₄O₃₁]₂}, consisting of a network of MO₆ (M = Fe, Mo) octahedral and PO₄ tetrahedral linked through their vertices. The connectivity of the building blocks with two pairs of face-sharing dinuclear Fe(II) clusters of the formula of [Fe^II ₂(H₂O)₄O₅] on which a phosphate group is hanging gives rise to one-dimensional chains with eight-membered apertures. The remarkable hydrogen bonded interactions between the chains form a unique and interesting framework with three-dimensional intersecting tunnels where the protonated nicotine molecules as structuring templates and crystallization water molecules are situated.     

Effect of the modifier ion on the properties of MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> pigments

Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow- orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color.     

Synthesis,molecular, crystal and electronic structure of [RuCl<Subscript>2</Subscript>(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>(3,5-Me<Subscript>2</Subscript>HPz)<Subscript>2</Subscript>]

The reaction of [RuCl₂(PPh₃)₃] complex with dimethylpyrazole has been examined. A new ruthenium complex—[RuCl₂(PPh₃)₂(3,5-Me₂HPz)₂] has been obtained and characterized by IR, ¹H NMR and UV-VIS measurements. Crystal and molecular structure of the complex has been determined. The electronic structure of the complex has been calculated by TDDFT method.     

Kinetics of isothermal decomposition of ZnSeO<Subscript>3</Subscript> and CdSeO<Subscript>3</Subscript>

The kinetics of decomposition of ZnSeO₃ and CdSeO₃ was studied under isothermal heating on a derivatograph. The values of activation energy, pre-exponential factor in Arrhenius equation and change of entropy were calculated for the formation of the activated complex by the reagent. The dependencies observed are interpreted according to the generalized perturbation theory of chemical reactivity.     

Chemical bonding and electronic structure of LaMnO<Subscript>3</Subscript> and La<Subscript>0.75</Subscript>MnO<Subscript>3</Subscript> orthorhombic crystals

The electronic structure of the LaMnO₃ orthorhombic crystal of a stoichiometric composition and of La_0.75MnO₃ crystals with a La vacancy in the unit cell is calculated in the LSDA+U approximation of density functional theory. The calculations showed that LaMnO₃ is an insulator with a forbidden gap of 0.5 eV and with antiferromagnetic ordering of magnetic moments. The magnetic moment on the manganese ions is 3.78 BM. The La atom has ionic bonds in the lattice, while the bond between oxygen and manganese is covalent. After lanthanum has been removed, geometry optimization of the unit cell leads to La_0.75MnO₃ stable structures. In one of the structures, which is lower in energy, the states of manganese may be attributed to Mn⁴⁺ ions. In both structures with removed lanthanum, the oxygen ions have reduced effective charge, so that one can speak about O^? ions appearing along with O^2? in the structure. The oxygen, as well as lanthanum and manganese, ions are nonequivalent in these structures; their nonequivalence is primarily reflected by the local densities of states. This leads to charge and magnetic nonequivalence of ions. In La_0.75MnO₃ crystals, the degree of bond covalence between manganese and oxygen decreases.     

Crystal structure of a new ternary molybdate in the Rb<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-Eu<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript>-Hf(MoO<Subscript>4</Subscript>)<Subscript>2</Subscript> system

A ternary salt system Rb₂MoO₄-Eu₂(MoO₄)₃-Hf(MoO₄)₂ was studied in the subsolidus area by X-ray phase analysis. A novel ternary molybdate, Rb_4.98Eu_0.86Hf_1.11(MoO₄)₆, formed in the system. The Rb_4.98Eu_0.86Hf_1.11(MoO₄)₆ rubidium-europium-hafnium molybdate crystals were grown by solution-melt crystallization under the spontaneous nucleation conditions. The structure and composition of this compound were refined by single crystal X-ray diffraction (X8 APEX automated diffractometer, MoK _α radiation, 1753 F(hkl), R = 0.0183). The crystals are trigonal, a = b = 10.7264(1) Å, c = 38.6130(8) Å, V = 3847.44(9) ų, Z = 6, space group R \(\bar 3\) c. The three-dimensional mixed framework of the structure comprises Mo tetrahedra and two types of octahedra, (Eu,Hf)O₆ and HfO₆. The large cavities of the framework include two types of the rubidium atom. The distribution of the Eu³⁺ and Hf⁴⁺ cations over two crystallographic positions was refined.     

Electronic energy structure of As<Subscript>2</Subscript>S<Subscript>3</Subscript>, AsSI,AgAsS<Subscript>2</Subscript>, and TiS<Subscript>2</Subscript> semiconductors

Quantum-mechanical calculations with the FEFF8 code were used to study the electronic energy structure of 200-atomic clusters of As₂S₃, AsSI, AgAsS₂, and TiS₂ semiconductor compounds. The calculated local partial densities of electronic states are compared with the sulfur K and L X-ray emission spectra and sulfur K absorption spectra for fine powders of these compounds. Good agreement between theory and experiment has been obtained.     

Towards high-performance cathode materials for lithium-ion batteries: Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-coated LiNi<Subscript>0.8</Subscript>Co<Subscript>0.15</Subscript>Zn<Subscript>0.05</Subscript>O<Subscript>2</Subscript>

Zn-doped LiNi_0.8Co_0.2O₂ exhibits impressive electrochemical performance but suffers limited cycling stability due to the relative large size of irregular and bare particle which is prepared by conventional solid-state method usually requiring high calcination temperature and prolonged calcination time. Here, submicron LiNi_0.8Co_0.15Zn_0.05O₂ as cathode material for lithium-ion batteries is synthesized by a facile sol-gel method, which followed by coating Al₂O₃ layer of about 15 nm to enhance its electrochemistry performance. The as-prepared Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂ cathode delivers a highly reversible capacity of 182 mA h g^?1 and 94% capacity retention after 100 cycles at a current rate of 0.5 C, which is much superior to that of bare LiNi_0.8Co_0.15Zn_0.05O₂ cathode. The enhanced electrochemistry performance can be attributed to the Al₂O₃-coated protective layer, which prevents the direct contact between the LiNi_0.8Co_0.15Zn_0.05O₂ and electrolyte. The escalating trend of Li-ion diffusion coefficient estimated form electrochemical impedance spectroscopic (EIS) also indicate the enhanced structural stability of Al₂O₃-coated LiNi_0.8Co_0.15Zn_0.05O₂, which rationally illuminates the protection mechanism of the Al₂O₃-coated layer.     

Structure and some properties of [UO<Subscript>2</Subscript>CrO<Subscript>4</Subscript>{CH<Subscript>3</Subscript>CON(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>}<Subscript>2</Subscript>]

A new complex [UO₂CrO₄{CH₃CON(CH₃)₂}₂] (I) was studied by thermal analysis, IR spectroscopy, and X-ray crystallography. The crystals are monoclinic: a = 13.8108(11) Å, b = 8.6804(7) Å, c = 13.0989(10) Å, β = 104.777(1)°, V = 1518.4(2) ų, space group P2₁/c, Z = 4, R = 2.39%. The structure of I contains infinite chains of the [UO₂CrO₄{CH₃CON(CH₃)₂}₂] composition running along [001]; the complex belongs to the AT¹¹M¹ ₂ crystal-chemical group (A = UO ₂ ²⁺ , T¹¹ = CrO ₄ ^2? , M¹ = CH₃CON(CH₃)₂) of uranyl complexes. The chains are linked into a three-dimensional framework due to hydrogen bonds between oxygen atoms of chromate ions and hydrogen atoms of methyl groups of the dimethylacetamide.     

Synthesis and characterization of Co<Subscript>0.8</Subscript>Zn<Subscript>0.2</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

Cobalt zinc ferrite, Co_0.8Zn_0.2Fe₂O₄, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate. The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been determined as Co_0.8Zn_0.2Fe₂(C₄H₂O₄)₃·6N₂H_4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements.     

Orientational disorder in crystal structures of (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>ZrF<Subscript>7</Subscript> and (NH<Subscript>4</Subscript>)<Subscript>3</Subscript>NbOF<Subscript>6</Subscript>

Crystal structures of (NH₄)₃ZrF₇ (I) and (NH₄)₃NbOF₆ (II) are refined by X-ray diffraction at room temperature. The compounds are isostructural and belong to the structural type of elpasolite: space group F23; a(I) = 9.4185(3) Å, a(II) = 9.3371(5) Å; V(I) = 835.50(5) ų, V(II) = 814.02(8) ų; Z = 4; R(I) = 0.0145, and R(II) = 0.0138. The refinement of the structures in the space group Fm3m yields abnormally short X-X distances in the pentagonal bipyramid MX₇ (X = F, O). The oxygen atom in II is identified by Nb-X distances and occupies one of the axial vertices of the bipyramid. The Nb atom in II is statistically distributed over the position 24f, while Zr in I resides in the symmetry center. The pentagonal bipyramid MX₇ has six independent orientations in I and twelve in II. One of three crystallographically independent ammonium groups of the structures is disordered over six or twelve equivalent orientations.