Showing papers on "Inorganic compound published in 1993"

Observation of the spin-Peierls transition in linear Cu2+ (spin-1/2) chains in an inorganic compound CuGeO3

Abstract: The magnetic susceptibility of single-crystal ${\mathrm{CuGeO}}_{3}$, a linear ${\mathrm{Cu}}^{2+}$ (spin-1/2) chain compound, was measured. The susceptibilities in all the directions rapidly drop to small constant values with decreasing temperature below a phase transition temperature near 14 K. The magnetic-field dependence of the transition temperature quantitatively agrees with both theoretical predictions and experimental results for organic spin-Peierls systems. This Letter is the first report of an unambiguous determination of the existence of the spin-Peierls transition in an inorganic compound.

Large second-order optical polarizabilities in mixed-valency metal complexes

Abstract: THE potential development of optoelectronic devices based on the nonlinear polarization of molecular materials has aroused much recent interest1,2. The search for large second-order electric susceptibilities (that is, proportional to the square of an applied electric field) has concentrated on acentric organic or organometallic chromophores with an organic π-electron system coupling electron donor and acceptor groups3–6. It is conceivable that mixed-valence compounds characterized by an intervalence charge-transfer (IVCT) transition7, in which the donor and acceptor centres are both metal atoms, might also have the potential to provide a large second-order response8, but this possibility has not been widely explored. Here we report the first hyperpolarizability, β, of a bimetallic complex ion, [(CN)5Ru-μCN-Ru(NH3)5]- (I in Fig. 1), and a novel organometallic analogue, [(η5-C5H5)Ru(PPh3)2-μ-CN-Ru(NH3)5]3+ (II). Measurements of β (which is related to the bulk second-order response) in solution at a wavelength of 1,064 nm using the newly developed hyper-Rayleigh scattering technique9,10 give values greater than 10–27 e.s.u., which are among the largest reported for solution species. The ease with which the energy of the IVCT transition can be modified suggests that there may be considerable potential for this class of chromophore in nonlinear optical devices.

Metal Organic Resin Derived Barium Titanate: I, Formation of Barium Titanium Oxycarbonate Intermediate

Abstract: Crystallization of BaTiO[sub 3] from an X-ray amorphous, metal organic precursor was investigated by comparing samples heated in O[sub 2], air, argon, and CO[sub 2]. It is evident that an intermediate barium titanium oxycarbonate phase forms between 500 and 620C and that BaTiO[sub 3] forms directly by the endothermic decomposition of this phase between 635 and 700C. From thermodynamic calculations, thermal analysis, X-ray diffraction, and Raman spectroscopy, it is concluded that the intermediate oxycarbonate is a highly disordered, metastable, and weakly crystalline phase with a stoichiometry close to Ba[sub 2]Ti[sub 2]O[sub 5]Co[sub 3].

Structure and superconductivity of the infinite-layer compound (Ca1−ySry)1−xCuO2−z

Abstract: Microstructure and superconducting properties of the infinite-layer compound A 1− x CuO 2− z (A=Ca 1− y Sr y ) have been investigated by high-resolution electron microscopy as well as magnetization and resistivity measurements. The alkaline earth deficient samples always contain defect-layers inserted almost randomly into the parent simple structure, where we suggest that the A cation vacancies are concentrated. High-resolution electron microscopy observations reveal that oxygen deficiency can simultaneously occur within the central CuO 2 sheet of the defect layer for the sake of charge compensation for the A deficiency. p-type superconductivity with a maximum T c of 110 K is realized if the oxygen defects are filled in by application of high oxygen pressure on high-pressure synthesis ( z ∼0). On the other hand, n-type superconductivity also occurs in the same structure when oxygen deficency is increased so that z > x by a heat-treatment in a reducing atmosphere under high pressure. The fundamental relationship between structure and superconductivity is discussed on the basis of the demonstrated structural uniqueness of the title compound.

An X-ray photoemission spectroscopy study of interlayer charge transfer in some misfit layer compounds

Abstract: The misfit layer compounds with a general formula (MX)1+ delta TX2 (with M=Sn, Pb, Bi or rare earth metal; X=S, Se; T=Ti, V, Cr, Nb, Ta and 0.05< delta <0.25) have a stacking of MX double layers with a NaCl-type structure alternated by TX2 sandwiches. The unit cell axes in the plane of the layers of both subsystems are equal in the b direction but are incommensurate in the a direction. To understand the stability of this remarkable and ordered stacking of the two different layers, charge transfer from the MX subsystem to the TX2 subsystem has been suggested. In this study misfit layer compounds with Sn, Pb and Bi as the M element have been investigated with X-ray photoelectron spectroscopy. The information obtained from the core levels shows that for the Sn and Pb containing compounds the Pb and Sn atoms are divalent, and no significant charge transfer takes place between the layers. The spectra of the Bi misfit layer compound indicate a valency close to three for Bi. The stability of the misfit layer compounds is attributed to the presence of covalent interlayer bonds.

First-principles investigation of visible light emission from silicon-based materials.

Abstract: The atomic and electronic structure of various Si-based layered structures is calculated using pseudopotential density-functional theory and a self-energy approach. A silicon-hydrogen compound, consisting of a stacking in the [111] direction of double layers of Si terminated with H, is found to have an almost direct band gap of 2.75 eV. Substituting OH groups for H atoms leads to the compound siloxene, which is found to have a direct band gap of ∼1.7 eV. Investigations of the band-edge states and calculations of matrix elements show that these direct transitions are very strong

The ab initio calculation of inner sphere reorganization energies of inorganic redox couples

Abstract: Values or the inner-sphere reorganization energies (λ i ) for a number or small-molecule inorganic redox couples (NO + /NO, NO 2 + /NO 2 , NO 2 /NO 2 - , N 3 /N 3 - , O 2 /O 2 - , O 3 /O 3 - , SO 2 /SO 2 - , ClO/ClO - , ClO/ClO 2 - , and Cl 2 /Cl 2 - ) have been calculated by ab initio methods. The λ i values were calibrated by comparing calculated bond lengths/angles, electron affinities, and ionization potentials with experimental data and were round to be accurate to within ±2 kcal mol -1 or better

Irreversible binding of dioxygen and other gases to a half-sandwich ruthenium(II) complex: X-ray structure of [Ru(η2-O2)(η5-C5Me5)(Ph2PCH2CH2PPh2)]PF6

Abstract: The half-sandwich compound [Ru(η5-C5Me5)(dppe)]Cl 1 is shown to coordinate simple inorganic gases viz. H2, Cl2, NO and O2; of these the side-on bonded peroxide [Ru(η2-O2)(η5-C5Me5)(dppe)]+2 is described in more detail including its X-ray crystal structure.

Multiple oxide sol, its production and base material

Abstract: PURPOSE: To obtain a sol in which colloid particles having low refractive index are dispersed by dispersing multiple oxide colloid particles consisting of silica and an inorganic compound other than silica into water and/or an organic solvent and to obtain a base material for low reflection by using the colloid particles. CONSTITUTION: The multiple oxide sol is obtained by dispersing the multiple oxide colloid particles having 1.36-1.44 refractive index and consisting of the silica and the inorganic compound other than the silica into water and/or the organic solvent. The multiple oxide sol is produced by following three processes 1-3. In the process 1, colloid particles consisting of the silica and the inorganic compound other than the silica are produced by simultaneously adding a silicate of an alkali metal, ammonium or organic base and the alkali-soluble inorganic compound into an alkali aq. solution of pH ≥10. In the process 2, a part of elements other than silicon and oxygen is removed (by an acid or cation exchange resin). In the process 3, the surface of the colloid particles obtained in the process 2 is coated with a coating film. COPYRIGHT: (C)1995,JPO

Substitution-induced midgap states in the mixed oxides RxBa1-xTiO3- delta with R=Y, La, and Nd.

Abstract: Changes induced in the electronic structure of BaTiO 3 by substitutions of R=Y, La, or Nd for Ba to form the mixed oxides R x Ba 1-x TiO 3-δ have been investigated using ultraviolet photoelectron spectroscopy Substitution of formally R 3+ ions for Ba 2+ leads to the introduction of filled states in the band gap that are shown by resonant-photoemission measurements to have significant Ti 3d character, consistent with a Mott-Hubbard-insulator description for these oxides Various contributions to the binding energy and width of these states are considered

Temperature dependence of the quenching of O(1S) by simple inorganic molecules

Abstract: The quenching of metastable O(1S) atoms by H2 , O2 , CO, CO2 , N2O, and SF6 was studied in the temperature range 210–470 K. Very low concentrations of O(1S) atoms were generated in the pulsed vacuum ultraviolet (VUV) Lα photolyses of N2O and CO2 . The atoms were detected by their forbidden emission at around 557.7 nm, the intensity of which was enhanced by the formation of exciplexes in the presence of Ar. The quenching by H2 and SF6 is very inefficient and occurs without a significant activation energy. The rate constants for the quenching by CO and CO2 can be represented by activation energies near 10 kJ mol−1 but very different frequency factors. The collisions of O(1S) with O2 and N2O lead to different products which likely are formed with different activation energies. It is proposed that generally quenching of O(1S) proceeds by diabatic processes.

Reaction of boron atoms with carbon dioxide: matrix and ab initio calculated infrared spectra of OBCO

Abstract: Pulsed laser evaporated boron atoms codeposited with Ar/CO 2 samples give a strong product band at 18634 cm -1 that shows boron, carbon, and oxygen isotopic shifts Ab initio calculations predict two strong infrared bands for the BOCO addition product and one strong band, which scales to the observed band position, for the OBCO insertion product The calculated and observed frequencies exhibit isotopic shifts appropriate for an «antisymmetric» O-B, C-O stretching fundamental in a bent OBCO molecule

Antibacterial electret material

Abstract: An antibacterial electret material which consists of a synthesized organic polymer having a volume resistivity of not less than 1013 Ω·cm and containing 0.01 to 2% by weight of one kind of electret stabilizer selected from the group composed of a hindered amine compound, a nitrogen-containing hindered phenol compound, a metallic salt hindered phenol compound, a phenol compound, a sulfur compound and a phosphorus compound and 0.1 to 4% by weight of metal ion-containing inorganic compound, and which has a surface density of charge of not less than 1×10-10 coulomb/cm2.