Gas-phase oxidation reactions of Ta2+: synthesis and properties of TaO(2+) and TaO2(2+)

Gas-phase reactions of Ta(2+) and TaO(2+) with oxidants, including thermodynamically facile O-atom donor N(2)O and ineffective donor CO, as well as intermediate donors C(2)H(4)O (ethylene oxide), H(2)O, O(2), CO(2), NO, and CH(2)O, were studied by Fourier transform ion cyclotron resonance mass spectrometry. All oxidants reacted with Ta(2+) by electron transfer yielding Ta(+), in accord with the high second ionization energy of Ta (ca. 16 eV). TaO(2+) was also produced with N(2)O, H(2)O, O(2), and CO(2), oxidants with ionization energies above 12 eV; CO reacted only by electron transfer. The following charge separation products were also observed: TaN(+) and TaO(+) with N(2)O; and TaO(+) with O(2), CO(2), and CH(2)O. TaOH(2+), formed with H(2)O, reacted with a second H(2)O by proton transfer. TaO(2+) abstracted an electron from N(2)O, H(2)O, O(2), CO(2), and CO. Oxidation of TaO(2+) by N(2)O was also observed to produce TaO(2)(2+); on the basis of density functional theory (DFT) results, this species is a dioxide, {O-Ta-O}(2+). TaO(2)(2+) reacted by electron transfer with N(2)O, CO(2), and CO to give TaO(2)(+). Additionally, it was found that TaO(2)(2+) oxidizes CO to CO(2) and that it acts as a catalyst in the oxidation of CO by N(2)O. TaO(2)(2+) also activates H(2) to form TaO(2)H(2+). On the basis of the rates of electron transfer from N(2)O, CO(2), and CO to Ta(2+), TaO(2+), and TaO(2)(2+), the following estimates were made for the second ionization energies of Ta, TaO, and TaO(2): IE[Ta(+)] = 15.8 ± 0.3 eV, IE[TaO(+)] = 16.0 ± 0.5 eV, and IE[TaO(2)(+)] = 16.9 ± 0.4 eV. These IEs, together with recently reported bond dissociation energies, D[Ta(+)-O] and D[OTa(+)-O], result in the following bond energies: D[Ta(2+)-O] = 657 ± 58 kJ mol(-1) and D[OTa(2+)-O] = 500 ± 63 kJ mol(-1), the first of which is in good agreement with the value obtained by DFT.     

Phase relationships in the BaO-Ga2O3-Ta2O5 system and the structure of Ba6Ga21TaO40

Phase relationships in the BaO-Ga(2)O(3)-Ta(2)O(5) ternary system at 1200 °C were determined. The A(6)B(10)O(30) tetragonal tungsten bronze (TTB) related solution in the BaO-Ta(2)O(5) subsystem dissolved up to ~11 mol % Ga(2)O(3), forming a ternary trapezoid-shaped TTB-related solid solution region defined by the BaTa(2)O(6), Ba(1.1)Ta(5)O(13.6), Ba(1.58)Ga(0.92)Ta(4.08)O(13.16), and Ba(6)GaTa(9)O(30) compositions in the BaO-Ga(2)O(3)-Ta(2)O(5) system. Two ternary phases Ba(6)Ga(21)TaO(40) and eight-layer twinned hexagonal perovskite solid solution Ba(8)Ga(4-x)Ta(4+0.6x)O(24) were confirmed in the BaO-Ga(2)O(3)-Ta(2)O(5) system. Ba(6)Ga(21)TaO(40) crystallized in a monoclinic cell of a = 15.9130(2) ?, b = 11.7309(1) ?, c = 5.13593(6) ?, β = 107.7893(9)°, and Z = 1 in space group C2/m. The structure of Ba(6)Ga(21)TaO(40) was solved by the charge flipping method, and it represents a three-dimensional (3D) mixed GaO(4) tetrahedral and GaO(6)/TaO(6) octahedral framework, forming mixed 1D 5/6-fold tunnels that accommodate the Ba cations along the c axis. The electrical property of Ba(6)Ga(21)TaO(40) was characterized by using ac impedance spectroscopy.     

Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7): a structure with tunable density of Na(+) vacancies

A series of samples with the composition Ca(1)(-)(x)Na(2)(x)Al(2)B(2)O(7) (0 < x < or = 1) was investigated and a hexagonal structure with unusually large range of homogeneity (at least from x = 0.01 to 0.95) was revealed. The hexagonal phase consists of [Al(2)B(2)O(7)](infinity)(2)(-) lamellae stacked along the c axis, as in CaAl(2)B(2)O(7) and Na(2)Al(2)B(2)O(7). Nevertheless, the configuration and stacking sequence of the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae are different in these three structures. In the hexagonal structure of Ca(1)(-)(x)()Na(2)(x)()Al(2)B(2)O(7), Ca and half Na cations (Na1) statistically occupy the same crystallographic site which is located between the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae, the other half Na cations (Na2) distribute in the planes bisecting the [Al(2)B(2)O(7)](infinity)(2)(-) lamellae. Depending on the composition, the site occupation factor of Na2 site can vary in the same range as x, leading to a tunable density of Na(+) vacancies in the structure. The AlO(4) tetrahedra and BO(3) triangles in the structure tilt in appropriate ways to improve the bond valence sum of Na2 cations which are not sufficiently bonded to the anions.     

Design of energy band alignment at the Zn(1-x)Mg(x)O/Cu(In,Ga)Se2 interface for Cd-free Cu(In,Ga)Se2 solar cells

The electronic band structure at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface was investigated for its potential application in Cd-free Cu(In,Ga)Se(2) thin film solar cells. Zn(1-x)Mg(x)O thin films with various Mg contents were grown by atomic layer deposition on Cu(In(0.7)Ga(0.3))Se(2) absorbers, which were deposited by the co-evaporation of Cu, In, Ga, and Se elemental sources. The electron emissions from the valence band and core levels were measured by a depth profile technique using X-ray and ultraviolet photoelectron spectroscopy. The valence band maximum positions are around 3.17 eV for both Zn(0.9)Mg(0.1)O and Zn(0.8)Mg(0.2)O films, while the valence band maximum value for CIGS is 0.48 eV. As a result, the valence band offset value between the bulk Zn(1-x)Mg(x)O (x = 0.1 and x = 0.2) region and the bulk CIGS region was 2.69 eV. The valence band offset value at the Zn(1-x)Mg(x)O/CIGS interface was found to be 2.55 eV after considering a small band bending in the interface region. The bandgap energy of Zn(1-x)Mg(x)O films increased from 3.25 to 3.76 eV as the Mg content increased from 0% to 25%. The combination of the valence band offset values and the bandgap energy of Zn(1-x)Mg(x)O films results in the flat (0 eV) and cliff (-0.23 eV) conduction band alignments at the Zn(0.8)Mg(0.2)O/Cu(In(0.7)Ga(0.3))Se(2) and Zn(0.9)Mg(0.1)O/Cu(In(0.7)Ga(0.3))Se(2) interfaces, respectively. The experimental results suggest that the bandgap energy of Zn(1-x)Mg(x)O films is the main factor that determines the conduction band offset at the Zn(1-x)Mg(x)O/Cu(In(0.7)Ga(0.3))Se(2) interface. Based on these results, we conclude that a Zn(1-x)Mg(x)O film with a relatively high bandgap energy is necessary to create a suitable conduction band offset at the Zn(1-x)Mg(x)O/CIGS interface to obtain a robust heterojunction. Also, ALD Zn(1-x)Mg(x)O films can be considered as a promising alternative buffer material to replace the toxic CdS for environmental safety.     

Substitutional mechanism of Ni into the wide-band-gap semiconductor InTaO4 and its implications for water splitting activity in the wolframite structure type

The mechanism of Ni substitution into the oxide semiconductor InTaO(4) has been studied through a combination of structural and spectroscopic techniques, providing insights into its previously reported photoactivity. Magnetic susceptibility and X-ray absorption near-edge spectroscopy (XANES) measurements demonstrate that nickel is divalent within the host lattice. The combined refinement of synchrotron X-ray and neutron powder diffraction data indicates that the product of Ni doping has the stoichiometry of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) with a solubility limit of x ≈ 0.18, corresponding to 12% Ni on the In site. Single-phase samples were only obtained at synthesis temperatures of 1150 °C or higher due to the sluggish reaction mechanism that is hypothesized to result from small free energy differences between (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds with different x values. Undoped InTaO(4) is shown to have an indirect band gap of 3.96 eV, with direct optical transitions becoming allowed at photon energies in excess of 5.1 eV. Very small band-gap reductions (less than 0.2 eV) result from Ni doping, and the origin of the yellow color of (In(1-x)Ni(2x/3)Ta(x/3))TaO(4) compounds instead results from a weak (3)A(2g) → (3)T(1g) internal d → d transition not associated with the conduction or valence band that is common to oxide compounds with Ni(2+) in an octahedral environment.     

Na(4)Mn(0.5)P(0.5)O(5): Synthesis of a Novel Mixed-Metal Manganese(VII)/Phosphorus(V) Oxide via Hydroxide Flux

Vibrant blue crystals of Na(4)Mn(0.5)P(0.5)O(5) were synthesized via a sodium hydroxide flux. The X-ray structural analysis showed that this sodium manganese(VII) phosphorous oxide crystallizes in an orthorhombic lattice with a = 8.967(3) ?, b = 7.291(3) ?, c = 8.090(3) ?: Pnma (No. 62); Z = 4. The manganese and phosphorus cations equally share one crystallographic site and are tetrahedrally coordinated. The (Mn,P)O(4) tetrahedra are held together by sodium cations via Na-O bonds forming an ionic solid, [Na(4)O](2+)[(Mn(0.5)P(0.5))O(4)](2)(-). The synthesis, structure, thermal property and infrared spectroscopy of the title compound are presented in this paper.     

Comparison of Adsorption Probabilities of O(2) and CO on Copper Cluster Cations and Anions

Reactions of size-selected copper cluster cations and anions, Cu(n)(±), with O(2) and CO have been systematically investigated under single collision conditions by using a tandem-mass spectrometer. In the reactions of Cu(n)(±) (n = 3-25) with O(2), oxidation of the cluster is prominently observed with and without releasing Cu atoms at the collision energy of 0.2 eV. The reactivity of Cu(n)(+) is governed to some extent by the electronic shell structure; the relatively small reaction cross sections observed at n = 9 and 21 correspond to the electronic shell closings, and those at odd sizes in n ≤ 16 match with the clusters having no unpaired electron. On the other hand, the reactivity of Cu(n)(-) exhibits no remarkable decrease by the electronic shell closings and the even-numbered electrons. These behaviors may be due to an influence of the electron detachment of the reaction intermediate, Cu(n)O(2)(-). Both the cations and anions show the dominant formation of Cu(n-1)O(2)(±) in n ≤ 16 and Cu(n)O(2)(±) in n ≥ 17 in the experimental time window. By contrast, Cu(n)(-) (n = 3-11) do not react with CO at the collision energy of 0.2 eV, while Cu(n)(+) (n = 3-19) adsorb CO though the cross sections are relatively small. The difference in the reactivity between the charge states can be understood in terms of the frontier orbitals of the Cu cluster and O(2) or CO.     

Oxysulfide Sm(2)Ti(2)S(2)O(5) as a stable photocatalyst for water oxidation and reduction under visible light irradiation (lambda < or = 650 nm)

A Ti-based oxysulfide, Sm(2)Ti(2)S(2)O(5), was studied as a visible light-driven photocatalyst. Under visible light (440 nm < or = lambda < or = 650 nm) irradiation, Sm(2)Ti(2)S(2)O(5) with a band gap of approximately 2 eV evolved H(2) or O(2) from aqueous solutions containing a sacrificial electron donor (Na(2)S-Na(2)SO(3) or methanol) or acceptor (Ag(+)) without any noticeable degradation. This oxysulfide is, therefore, a stable photocatalyst with strong reduction and oxidation abilities under visible-light irradiation. The electronic band structure of Sm(2)Ti(2)S(2)O(5) was calculated using the plane-wave-based density functional theory (DFT) program. It was elucidated that the S3p orbitals constitute the upper part of the valence band and these orbitals make an essential contribution to the small band gap energy. The conduction and valence bands' positions of Sm(2)Ti(2)S(2)O(5) were also determined by electrochemical measurements. It indicated that conduction and valence bands were found to have satisfactory potentials for the reduction of H(+) to H(2) and the oxidation of H(2)O to O(2) at pH = 8. This is consistent with the results of the photocatalytic reactions.     

LnCu_2O_4(Ln=Gd,Nd)电子结构的XPS研究

用 XPS测定了 LnCu2O4(Ln=Gd, Nd)的内层和价层电子能谱,观察到 LnCu2O4中稀土金属的 3d电子结合能比相应的稀土金属简单氧化物的 3d结合能低 0.8～ 0.9 eV,而 Cu的 2p电子结合能比 CuO的高 0.4～ 0.5 eV,因此推断在 LnCu2O4的 Ln－ O－ Cu链中存在 Cu→ O→ Ln电荷转移 .XPS分析还表明 LnCu2O4的 Cu原子上有较低的电荷密度,但不存在混合价态 .此外,通过比较价电子能谱,发现 NdCu2O4的 Ln 4f Cu 3d O 2p价带中心比 GdCu2O4的价带中心向 Fermi能级移近了 3.4 eV,而且 NdCu2O4的价带谱更窄 .     

Copper-complex-linked polytungsto-bismuthate (-antimonite) chain containing sandwich Cu(II) ions partially modified with imidazole ligand

Two sandwich-type complexes Na9n(Cu(im)4(H2O)2)1.5n(Cu(im)4(H2O))n[{Cu(im)4}{Na(H2O)2}3{Cu3(im)2(H2O)}(XW9O33)2]2n .(xH2O)n (im=imidazole, X=Bi (1), Sb(2), x=42.5 (1), 40 (2)) have been synthesized and structurally characterized. Basic frameworks of 1 and 2 are built from sandwich-type [{Na(H2O) 2} 3{Cu3(im)2(H2O)}(XW9O33)2](9-) (X=Bi or Sb) anions and [Cu(im) 4](2+) cations. The Cu(2+) and Na(+) ions in the central belt are coordinated by alpha-[XW9O33](9-) units, im, and water molecules to form {CuO4(im)}, {CuO4(H2O)}, and {NaO4(H2O)2} groups in which Cu (2+) ions are partially modified with im ligands. These groups connect alternately forming a six-membered ring including six alpha-[XW9O 33](9-) units. Neighboring anions are further linked by [Cu(im) 4](2+) cations to display an unprecedented anionic chain, which is first observed in sandwich-type tungsto-bismuthate (-antimonite) system. Two kinds of isolated copper complexes and sodium ions are located as counterions, which cause three-dimensional packings of 1 and 2 to present interesting cage structures. The magnetic properties for 1 and 2 both indicate dominant antiferromagnetic interactions among trinuclear Cu(II) clusters.     

LnCu2O4(Ln=Gd,Nd)电子结构的XPS研究

用XPS测定了LnCu2O4(Ln=Gd, Nd)的内层和价层电子能谱,观察到LnCu2O4中稀土金属的3d电子结合能比相应的稀土金属简单氧化物的3d结合能低0.8～0.9 eV,而Cu的2p电子结合能比CuO的高0.4～0.5 eV,因此推断在LnCu2O4的Ln－O－Cu链中存在Cu→O→Ln电荷转移.XPS分析还表明LnCu2O4的Cu原子上有较低的电荷密度,但不存在混合价态.此外,通过比较价电子能谱,发现NdCu2O4的Ln 4f Cu 3d O 2p价带中心比GdCu2O4的价带中心向Fermi能级移近了3.4 eV,而且NdCu2O4的价带谱更窄.     

Monovalent ion adsorption at the muscovite (001)-solution interface: relationships among ion coverage and speciation, interfacial water structure, and substrate relaxation

The interfacial structure between the muscovite (001) surface and aqueous solutions containing monovalent cations (3 × 10(-3) m Li(+), Na(+), H(3)O(+), K(+), Rb(+), or Cs(+), or 3 × 10(-2) m Li(+) or Na(+)) was measured using in situ specular X-ray reflectivity. The element-specific distribution of Rb(+) was also obtained with resonant anomalous X-ray reflectivity. The results demonstrate complex interdependencies among adsorbed cation coverage and speciation, interfacial hydration structure, and muscovite surface relaxation. Electron-density profiles of the solution near the surface varied systematically and distinctly with each adsorbed cation. Observations include a broad profile for H(3)O(+), a more structured profile for Li(+) and Na(+), and increasing electron density near the surface because of the inner-sphere adsorption of K(+), Rb(+), and Cs(+) at 1.91 ± 0.12, 1.97 ± 0.01, and 2.26 ± 0.01 ?, respectively. Estimated inner-sphere coverages increased from ~0.6 to 0.78 ± 0.01 to ~0.9 per unit cell area with decreasing cation hydration strength for K(+), Rb(+), and Cs(+), respectively. Between 7 and 12% of the Rb(+) coverage occurred as an outer-sphere species. Systematic trends in the vertical displacement of the muscovite lattice were observed within ~40 ? of the surface. These include a <0.1 ? shift of the interlayer K(+) toward the interface that decays into the crystal and an expansion of the tetrahedral-octahedral-tetrahedral layers except for the top layer in contact with solution. The distortion of the top tetrahedral sheet depends on the adsorbed cation, ranging from an expansion (by ~0.05 ? vertically) in 3 × 10(-3)m H(3)O(+) to a contraction (by ~0.1 ?) in 3 × 10(-3) m Cs(+). The tetrahedral tilting angle in the top sheet increases by 1 to 4° in 3 × 10(-3) m Li(+) or Na(+), which is similar to that in deionized water where the adsorbed cation coverages are insufficient for full charge compensation.     

First-principles density functional calculation of electrochemical stability of fast Li ion conducting garnet-type oxides

The research and development of rechargeable all-ceramic lithium batteries are vital to realize their considerable advantages over existing commercial lithium ion batteries in terms of size, energy density, and safety. A key part of such effort is the development of solid-state electrolyte materials with high Li(+) conductivity and good electrochemical stability; lithium-containing oxides with a garnet-type structure are known to satisfy the requirements to achieve both features. Using first-principles density functional theory (DFT), we investigated the electrochemical stability of garnet-type Li(x)La(3)M(2)O(12) (M = Ti, Zr, Nb, Ta, Sb, Bi; x = 5 or 7) materials against Li metal. We found that the electrochemical stability of such materials depends on their composition and structure. The electrochemical stability against Li metal was improved when a cation M was chosen with a low effective nuclear charge, that is, with a high screening constant for an unoccupied orbital. In fact, both our computational and experimental results show that Li(7)La(3)Zr(2)O(12) and Li(5)La(3)Ta(2)O(12) are inert to Li metal. In addition, the linkage of MO(6) octahedra in the crystal structure affects the electrochemical stability. For example, perovskite-type La(1/3)TaO(3) was found, both experimentally and computationally, to react with Li metal owing to the corner-sharing MO(6) octahedral network of La(1/3)TaO(3), even though it has the same constituent elements as garnet-type Li(5)La(3)Ta(2)O(12) (which is inert to Li metal and features isolated TaO(6) octahedra).     

Photocatalytic activity of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) for water splitting into H2 and O2

The photocatalytic activities of R3MO7 and R2Ti2O7 (R=Y, Gd, La; M=Nb, Ta) strongly depended on the crystal structure. Overall, photocatalytic water splitting into H2 and O2 proceeded over La3TaO7 and La3NbO7, which have an orthorhombic weberite structure, Y2Ti2O7 and Gd2Ti2O7, which have a cubic pyrochlore structure, and La2Ti2O7, which has a monoclinic perovskite structure. All of these materials are composed of a network of corner-shared octahedral units of metal cations (TaO6, NbO6, or TiO6); materials without such a network were inactive. The octahedral network certainly increased the mobility of electrons and holes, thereby enhancing photocatalytic activity.     

Sr14-xCaxCu24O41的芯能级光电子发射谱

The core-level X-ray photoelectron emission spectra of the quasi-one dimensional spin 1/2 antiferromagnetic system Sr14-xCaxCu24O41(x=0, 3.5, 6, 7, 8.4) were measured. The main peak of Cu2p3/2 was about 933.8 eV, and the full width of half maximum height was about 3.3 eV. Simulation of Cu2p3/2 by XPSPEAK41 shows that the percents of Cu2+ and Cu3+ in Sr14Cu24O41 are 92.13% and 7.87%, no obvious change to Cu2p core-level is observed by the partial substituting Ca for Sr, and the average valence of Cu in this system is estimated to be 2.08. The main peak of O1s is about 531.0 eV, and the weak shoulder toward the low binding energy direction can be considered as the contribution of Ca-O bond. The binding energies of Ca2p3/2 and Sr3d5/2 indicate that their valence in this system are both +2, without mixed valence.     

Synthesis, structure, and optical properties of the quaternary seleno-gallates NaLnGa4Se8 (Ln = La, Ce, Nd) and their comparison with the isostructural thio-gallates

Three new quaternary seleno-gallates containing rare-earth metals and sodium cations, have been synthesized by a solid-state route in evacuated quartz ampoules: Na LnGa 4Se 8 ( Ln = La( I), Ce ( II) and Nd ( III)). The synthesis involved the stoichiometric combination of sodium polyselenides, rare-earth metal, Ga 2Se 3, and Se or elemental Ga in place of Ga 2Se 3. Single-crystal structure analysis indicated that the compounds are isostructural to the thio-analogue, NaNdGa 4S 8. The structures of I- III are described in terms of layers of GaSe 4 tetrahedra joined by corner- and edge-sharing; the alkali-metal cations and the trivalent rare-earth metal cations occupy square antiprismatic sites between the layers. The optical properties of the compounds have been investigated and compared with the isostructural thio-gallate. The band gap of I was located around 2.65 eV. The band gaps of II and III were 2.66 and 2.73 eV, respectively, considerably narrower than their thio-analogues ( approximately 3.4 eV). The contraction of the band gap was attributed to the shift of the valence band to higher energy due to the involvement of higher energy (4p) Se orbitals. The 4f --> 5d gap of II is found to be located around 2.32 eV, which is 0.26 eV narrower than the thio-analogue is due to a greater dispersion of the Ln-(5d) band caused by more covalent Ce-Se bonds as well as rising of the f level energy.     

Synthesis and Characterization of a New Quasi-One-Dimensional Copper(II) Phosphate, Ba(2)Cu(PO(4))(2)

Crystals of Ba(2)Cu(PO(4))(2) have been grown in a low-temperature eutectic flux of 32% KCl and 68% CuCl (mp = 140 degrees C). The X-ray single-crystal structure analysis shows that this barium copper(II) phosphate crystallizes in a monoclinic lattice with a = 12.160(4) ?, b = 5.133(4) ?, c = 6.885(4) ?, beta = 105.42(4) degrees, and V = 414.3(4) ?(3); C2/m (No. 12); Z = 2. The structure has been refined by the least-squares method to a final solution with R = 0.020, R(w) = 0.026, and GOF = 1.05. The framework of the title compound consists of [Cu(PO(4))(2)](infinity) linear chains with Ba(2+) cations residing between these parallel chains. The chains are composed of an array of Cu(2+) cations that are doubly bridged by PO(4) anions. Each pair of bridging PO(4) tetrahedra are in a staggered configuration above and below the CuO(4) square plane, resulting in a linear chain with a long Cu---Cu separation distance, 5.13 ? ( identical withb). This quasi-one-dimensional framework is unusual among the Cu(2+)-based phosphates. Magnetic susceptibility data shows Curie-Weiss paramagnetic behavior in the range of ca. 190-300 K and a possible antiferro-to-ferromagnetic transition at approximately 8 K. In this paper, the synthesis, structure, and properties of the title compound are presented. A structural comparison to a closely related vanadyl (VO)(2+) phosphate, Ba(2)(VO)(PO(4))(2).H(2)O, as well as Na(2)CuP(2)O(7) will be discussed.     

Electronic structure of A- and B-site doped lanthanum manganites: a combined X-ray spectroscopic study

The electronic properties of a series of colossal magnetoresistance (CMR) compounds, namely LaMnO3, La(1-x)Ba(x)(MnO3 (0.2 < or = x < or = 0.55), La(0.76)Ba(0.24)Mn(0.84)Co(0.16)O3, and La(0.76)Ba(0.24)Mn(0.78)Ni(0.22)O3, have been investigated in a detailed spectroscopic study. A combination of X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES), X-ray absorption spectroscopy (XAS), and resonant inelastic X-ray scattering (RIXS) was used to reveal a detailed picture of the electronic structure in the presence of Ba, Co, and Ni doping in different concentrations. The results are compared with available theory. The valence band of La(1-x)()Ba(x)MnO3 (0 < or = x < or = 0.55) is dominated by La 5p, Mn 3d, and O 2p states, and strong hybridization between Mn 3d and O 2p states is present over the whole range of Ba concentrations. Co-doping at the Mn site leads to an increased occupancy of the e(g) states near the Fermi energy and an increase in the XPS valence band intensity between 0.5 and 5 eV, whereas the Ni-doped sample shows a lower density of occupied states near the Fermi energy. The Ni d states are located in a band spanning the energy range of 1.5-5 eV. XAS spectra indicate that the hole doping leads to mixed Mn 3d-O 2p states. Furthermore, RIXS at the Mn L edge has been used to probe d-d transitions and charge-transfer excitations in La(1-x)Ba(x)MnO3.     

A family of new glutarate compounds: synthesis, crystal structures of: Co(H2O)5L(1), Na2[CoL2] (2), Na2[L(H2L)4/2] (3), {[Co3(H2O)6L2](HL)2}.4H2O (4), {[Co3(H2O)6L2](HL)2}.10H2O (5), {[Co3(H2O)6L2]L2/2}.4H2O (6), and Na2{[Co3(H2O)2]L8/2].6H2O (7), and magnetic properties of 1 and 2 with H2L = HOOC-(CH2)3-COOH

Seven new glutaric acid complexes, Co(H 2O) 5L 1, Na 2[CoL 2] 2, Na 2[L(H 2L) 4/2] 3, {[Co 3(H 2O) 6L 2](HL) 2}.4H 2O 4, {[Co 3(H 2O) 6L 2](HL) 2}.10H 2O 5, {[Co 3(H 2O) 6L 2]L 2/2}.4H 2O 6, and Na 2{[Co 3(H 2O) 2]L 8/2].6H 2O 7 were obtained and characterized by single-crystal X-ray diffraction methods along with elemental analyses, IR spectroscopic and magnetic measurements (for 1 and 2). The [Co(H 2O) 5L] complex molecules in 1 are assembled into a three-dimensional supramolecular architecture based on intermolecular hydrogen bonds. Compound 2 consists of the Na (+) cations and the necklace-like glutarato doubly bridged [ C o L 4 / 2 ] 2 - infinity 1 anionic chains, and 3 is composed of the Na (+) cations and the anionic hydrogen bonded ladder-like [ L ( H 2 L ) 4 / 2 ] 2 - infinity 1 anionic chains. The trinuclear {[Co 3(H 2O) 6L 2](HL) 2} complex molecules with edge-shared linear trioctahedral [Co 3(H 2O) 6L 2] (2+) cluster cores in 4 and 5 are hydrogen bonded into two-dimensional (2D) networks. The edge-shared linear trioctahedral [Co 3(H 2O) 6L 2] (2+) cluster cores in 6 are bridged by glutarato ligands to generate one-dimensional (1D) chains, which are then assembled via interchain hydrogen bonds into 2D supramolecular networks. The corner-shared linear [Co 3O 16] trioctahedra in 7 are quaternate bridged by glutarato ligands to form 1D band-like anionic {[Co 3(H 2O) 2]L 8/2} (2+) chains, which are assembled via interchain hydrogen bonds into 2D layers, and between them are sandwiched the Na (+) cations. The magnetic behaviors of 1 and 2 obey the Curie-Weiss law with chi m = C/( T - Theta) with the Curie constant C = 3.012(8) cm (3) x mol (-1) x K and the Weiss constant Theta = -9.4(7) K for 1, as well as C = 2.40(1) cm (3) x mol (-1) x K and Theta = -2.10(5) K for 2, indicating weak antiferromagnetic interactions between the Co(II) ions.     

可见光响应光催化剂K4Ce2Ta10O30、K4Ce2Nb10O30及其固溶体的电子结构

基于密度泛函理论(DFT), 采用平面波赝势(PWP)以及广义梯度近似(GGA)方法, 对可见光响应的光催化剂K4Ce2Ta10O30、K4Ce2Nb10O30及其固溶体进行电子结构的第一性原理计算. 结果表明, 光催化剂K4Ce2Ta10O30和K4Ce2Nb10O30的导带分别主要由Ta 5d和Nb 4d组成, 处于高能级的电子未占据态的Ce 4f与其有很明显的重迭, 但由于其高度局域特性,不能很好地参与光生电子在导带中的传导, 从而对光催化活性的贡献很小;而其价带则由O 2p与Ta 5d (Nb 4d)的杂化轨道组成, 同时电子占据态的Ce 4f对价带也有一定的贡献, 各个电子轨道对能带结构的贡献决定了该系列可见光响应光催化剂的物理化学和光催化特性. 固溶体系列中随着Nb含量的增加, 其吸收光谱依次红移, 带隙变窄, 导带底变低, 光生电子的还原能力降低. 在固溶体K4Ce2Ta10-xNbxO30(x=2, 5, 8)中, 由于Ce 4f轨道对价带顶的贡献相对较小, 固溶体的价带顶低于K4Ce2Ta10O30、K4Ce2Nb10O30的价带顶, 光生空穴的氧化能力相对较强. 该系列光催化剂的电子结构分析结果与光催化水分解的活性实验结果有很好的一致性.