F+ and F⁻ affinities of simple N(x)F(y) and O(x)F(y) compounds

Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral and ionic N(x)F(y) and O(x)F(y) systems using coupled cluster theory with single and double excitations and including a perturbative triples correction (CCSD(T)) method with correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. To achieve near chemical accuracy (±1 kcal/mol), three corrections to the electronic energy were added to the frozen core CCSD(T)/CBS binding energies: corrections for core-valence, scalar relativistic, and first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory where possible. The calculated heats of formation are in good agreement with the available experimental values, except for FOOF because of the neglect of higher order correlation corrections. The F(+) affinity in the N(x)F(y) series increases from N(2) to N(2)F(4) by 63 kcal/mol, while that in the O(2)F(y) series decreases by 18 kcal/mol from O(2) to O(2)F(2). Neither N(2) nor N(2)F(4) is predicted to bind F(-), and N(2)F(2) is a very weak Lewis acid with an F(-) affinity of about 10 kcal/mol for either the cis or trans isomer. The low F(-) affinities of the nitrogen fluorides explain why, in spite of the fact that many stable nitrogen fluoride cations are known, no nitrogen fluoride anions have been isolated so far. For example, the F(-) affinity of NF is predicted to be only 12.5 kcal/mol which explains the numerous experimental failures to prepare NF(2)(-) salts from the well-known strong acid HNF(2). The F(-) affinity of O(2) is predicted to have a small positive value and increases for O(2)F(2) by 23 kcal/mol, indicating that the O(2)F(3)(-) anion might be marginally stable at subambient temperatures. The calculated adiabatic ionization potentials and electron affinities are in good agreement with experiment considering that many of the experimental values are for vertical processes.     

Determination of the stability constants of Pb–(DIPSO)x–(OH)y and Pb–(AMPSO)x–(OH)y systems

In this work, complexation between lead ion and the ligands 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) and N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO), which are commercial pH buffers, is presented. Both ligands form complexes with lead in their pH buffer range (between pH 6.5 and 8.5 for DIPSO and between pH 8.0 and 9.0 for AMPSO). The final models and the overall stability constants, which are reported here, were determined by direct current polarography and glass electrode potentiometry [only for the Pb–(DIPSO)_x–(OH)_y system] at 25.0 °C and 0.1 M KNO₃ ionic strength. For the Pb–(DIPSO)_x–(OH)_y system, the proposed final model contains PbL, PbL₂, PbL₂(OH), and PbL₂(OH)₂ with stability constants, as log β, of 3.4 ± 0.1, 6.35 ± 0.15, 12.8 ± 0.2, and 18.0 ± 0.3, respectively. For the Pb–(AMPSO)_x–(OH)_y system, the species observed are PbL, PbL(OH), and PbL(OH)₂ with stability constants, as log β, of 2.9 ± 0.5, 9.4 ± 0.1, and 14.5 ± 0.2, respectively. For AMPSO, the possible adsorption of the ligand at the mercury electrode surface was evaluated by alternating current polarography through calculation of the capacitance of the double layer.     

Zn_(2-x)GeO_(4-x-3y)N_(2y)催化剂的制备、表征及可见光催化性能

通过氮化Zn2GeO4制备了Zn2-xGeO4-x-3yN2y催化剂,其带边吸收由400nm的紫外光区扩展到600nm的可见光区。光催化产氧性能的结果表明,氮化温度为800℃时,制备的催化剂具有最大活性。不同助催化剂对产氧活性的影响研究表明,担载助催化剂能大大提高产氧活性,其中担载Co2O3的产氧活性可达未担载的3.8倍。     

M/(MgO)y(CeO2)1－y(M=Ni、Co、Cu)催化剂的催化甲烷燃烧性能

采用溶胶凝胶法制备了M/(MgO)_y(CeO2)_1－y(M=Ni、Co、Cu)催化剂. 研究了催化剂Ni/(MgO)y(CeO₂)_1－y催化活性与Ce含量的关系, 当y＝0.9时, 催化剂的活性和稳定性最好. 对比研究了(MgO)_0.9(CeO2)_0.1为载体, 负载Ni、Co、Cu活性组分的催化剂催化甲烷燃烧性能. 结果表明, 负载Cu的催化剂活性最好, 但二次评价后催化剂已烧结；负载Ni的催化剂活性与负载Cu的催化剂相差不大, 且稳定性最好, 经1000 ℃焙烧的Ni/(MgO)_0.9(CeO2)_0.1催化剂比表面仍有14.32 m₂•g^－1, 具有较高的催化活性和很好的热稳定性；负载Co的催化剂活性不如前两者, 稳定性居中, 但比表面降低得最少, 抗烧结能力强.     

Ammonia oxidation and charge compensation in the metal ammonia intercalates Li+x(NH+4)y′(NH3)y″TiS(x+y′)−

The lithium-ammonia intercalates of TiS₂, Li⁺_x(NH⁺₄)_y′(NH₃)_y″TiS^(x+y′)−, where 0.00 ≤ x ≤ 0.20, have been investigated by thermogravimetric analysis (TGA), vapor pressure measurements, X-ray powder diffraction, and SQUID magnetometry. TGA and vapor-pressure measurements indicate that ammonia deintercalation occurs by a distinct two-step process consistent with the ionic nature of these compounds. These materials are monophasic and crystallize in a 3R-type structure. The c lattice parameter increases linearly with increasing ammonia content, which may be associated with the diminution of the ion-dipole interaction of the cation(s) with the lone pair of ammonia. Compositional analysis by TGA shows that charge compensation occurs such that the total cationic concentration (x + y′) is constant at 0.22 ± 0.02. The Pauli paramagnetism of the conduction electrons corresponds to complete ionization of both lithium and ammonium, so that the driving force for the charge-transfer phenomenon is the transfer of 0.22 ± 0.02 electrons to the conduction band of TiS₂. The degree of NH₃ oxidation depends upon the relative intercalation rate of metal and NH₃.     

Synthesis of nanopowders of pentoxides Ta2y Nb2(1−y)O5

The processes of production of high purity nanopowders of niobium and tantalum pentoxide Ta_2y Nb_2(1–y)O₅ with a low content of fluorine and Nb₂O₅ in low-temperature polymorph were studied. Ceramic samples were prepared from a charge of solid solutions LiTa _y Nb_1–y O₃ and Li _x Na_1–x Ta _y Nb_1–y O₃ synthesized using coprecipitated pentoxide Ta_2y Nb_2(1–y)O₅. Therewith for solid solutions LixNa_1–x Ta _y Nb_1–y O₃ significantly larger values of high dielectric constant and ionic conductivity were achieved compared to the solid solutions obtained by using a mechanical mixture of Ta₂O₅ and Nb₂O₅. This converts solid solutions LixNa_1–x Ta _y Nb_1–y O₃ from acoustoelectronic and piezoelectric type of materials into the capacitor and ion-conductive type of solid materials.     

AC conductivity studies and relaxation behaviour in (LiX) y [(Li2O)0.6(P2O5)0.4](1 − y) glasses

The electrical conductivity of (LiX) _y [(Li₂O)_0.6(P₂O₅)_0.4]_(1???y) (X?=?Cl, Br, y?=?0, 0.1, 0.15, 0.2) glasses has been determined over a wide range of temperature and frequency by means of impedance spectroscopy. The real part of the frequency-dependent conductivity exhibits a simple power law feature, and the dimensionless frequency exponent n has been determined. The conductivity spectra show scaling behaviour when the conductivity spectra are scaled by ω/(σ _dc T) and ω/ω _p . The conductivity relaxation time and activation energy have been estimated from the modulus spectra. Increases of ionic conductivity values with addition of LiX content are in line with the decrease of activation energy and relaxation time.     

Novel red-emitting phosphors, (Mg(1−x−y)MnxDyy)Al2Si2O8 and (Mg(1−x−y)MnxTmy)Al2Si2O8

Mn⁴⁺ doped and Dy³⁺, Tm³⁺ co-doped MgAl₂Si₂O₈-based phosphors were prepared by conventional solid state reaction at 1,300 °C. They were characterized by thermogravimetry, differential thermal analysis, X-ray powder diffraction, photoluminescence, and scanning electron microscopy. The luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 600–715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a red emission can be attributed to the ²E → ⁴A₂ transitions of Mn⁴⁺.     

Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)速控步骤的反应机理研究北大核心CSCD

采用密度泛函理论(DFT)研究了C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)(x+y=4,x=1、2、3、4)表面吸附及速控步骤反应机理.计算了C_(3)H_(8)、CO_(2)和相应中间体在Ni_(x)Cu_(y)-B_(24)N_(28)表面的吸附能以及6条可能路径下的反应热和活化能.计算结果表明,C_(3)H_(8)和CO_(2)在Ni_(x)Cu_(y)-B_(24)N_(28)表面是物理吸附,C_(3)H_(8)+CO_(2)→CH_(3)CHCH_(3)+OCOH是最有利的路径,其在不同催化剂表面的活化能顺序是NiCu_(3)-B_(24)N_(28)(1.42 eV)、Ni_(2)Cu_(2)-B_(24)N_(28)(1.57 eV)、Ni_(3)Cu-B_(24)N_(28)(1.62 eV)、Ni_(4)-B_(24)N_(28)(1.75 eV).由此可知,在Ni_(x)Cu_(y)-B_(24)N_(28)催化CO_(2)氧化C_(3)H_(8)的体系中,Cu含量直接影响其催化活性,即NiCu_(3)-B_(24)N_(28)用于催化CO_(2)氧化C_(3)H_(8)有一定优势.     

复合稀土对α-Ni0.8Co0.05Al0.15(OH)2.15-2y(CO3)y·xH2O电化学性能的影响

为了同时改善固相共沉积法合成的α-Ni0.8Co0.05Al0.15(OH)2.15-2y(CO3)y·xH2O的常、高温充放电性能,样品经混合掺杂不同比率的La2O3,Sm2O3,Y2O3,Lu2O3以及La2O3+Y2O3后,作为模拟MH/Ni电池的正极材料,在不同温度下由恒流充放电和循环伏安测定其电化学性能.结果表明:复合掺加0.5%La2O3+1.0%Y2O3(质量分数),在0.5C和5C充放电下,30℃时可分别提高样品的放电比容量3.3%和4.7%,60℃时可分别提高17.4%和19.9%.同时也改善了高温放电电位.     

Synthesis, Structure and Dielectric Property of Ba_(1- x)Sr_xZr_yTi_(1- y)O_3

ＩｎｔｒｏｄｕｃｔｉｏｎＢａＴｉＯ３ｉｓａｓｔｒｏｎｇｄｉｅｌｅｃｔｒｉｃｍａｔｅｒｉａｌ，ｗｈｉｃｈｉｓｗｉｄｅｌｙｕｓｅｄｉｎｔｈｅｐｒｏｄｕｃｔｉｏｎｏｆｅｌｅｃｔｒｉｃｃｏｍｐｏｎｅｎｔｓｓｕｃｈａｓｃｅｒａｍｉｃｃａｐａｃｉｔｏｒ，ＰＴＣ，ｍｅｄｉｕｍａｍｐｌｉｆｅｒ［１］．Ｉｔｈａｓｔｈｅｈｉｇｈｅｓｔｄｉｅｌｅｃｔｒｉｃｃｏｎｓｔａｎｔａｔ１２０℃（ｃａ．１０４），ｗｈｉｌｅｉｔｓｄｉｅｌｅｃｔｒｉｃｃｏｎｓｔａｎｔａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｉｓｏｎｌｙ１／６ｏｆｔｈｅＣｕ…     

Synthesis and Properties of Colored Copper-Containing Apatites of Composition Ca5(PO4)3CuyO y + δ(OH)0.5 − y − δX0.5 (X = OH,F, Cl)

Ca₅(PO₄)₃Cu_yO _{y + δ}(OH)_{0.5 ? y ? δ}X_0.5 compounds (for X = OH, y = 0.01–0.3; for X = F, y = 0.01–0.1; for X = Cl, y = 0.1) have been synthesized by heat treatment of oxide-carbonate mixtures at 1150°C in air and have been characterized by X-ray diffraction, electronic spectroscopy, and magnetic measurements. The compounds have an apatite structure in which copper atoms substitute for part of the hydroxyl hydrogen atoms in hexagonal channels. The electronic spectrum shows two main absorption bands due to d-d transitions in copper(II) linearly coordinated to two oxygen atoms, as well as extra, weaker bands, whose contribution to the overall spectrum decreases with decreasing y. The latter are assignable to copper atoms occupying other sites in the crystal lattice. The temperature dependence of the magnetic susceptibility of the compounds obeys the Curie-Weiss law with a Curie constant close to zero. The Weiss constant characterizes the copper(II) content of the compounds and correlates qualitatively with the intensity of the main absorption bands in the visible spectrum. The fraction of copper(II) in the total amount of copper in the apatites increases in the substituent order X: Cl, OH, F, as well as upon the low-temperature annealing of the compounds in air. At the same time, copper(II) fraction depends only slightly on the total copper content. As the copper(II) content increases, the color of apatite changes from pink to dark claret.     

过渡金属团簇Nbn、Con(n≤4)和NbxCoy(x+y≤8)的芳香性

采用杂化密度泛函(DFT)方法优化了过渡金属纯团簇Nbn, Con(n≤4)和二元铌钴团簇NbxCoy(x+y≤8)的结构, 并计算了较稳定结构的NICS(核独立化学位移)值, 分析这些过渡金属团簇的成键情况, 讨论不同轨道对各过渡金属团簇芳香性的贡献, 发现在过渡金属团簇中, 除了具有s、p轨道贡献的σ、π芳香性外, 很重要的地d轨道的参与而形成的δ芳香性.     

Complete titanium substitution by boron in a tetragonal prism: exploring the complex boride series Ti(3-x)Ru(5-y)Ir(y)B(2+x) (0 ≤ x ≤ 1 and 1 < y < 3) by experiment and theory

Polycrystalline samples and single crystals of four members of the new complex boride series Ti(3-x)Ru(5-y)Ir(y)B(2+x) (0 ≤ x ≤ 1 and 1 < y < 3) were synthesized by arc-melting the elements in a water-cooled copper crucible under an argon atmosphere. The new silvery phases were structurally characterized by powder and single-crystal X-ray diffraction as well as energy- and wavelength-dispersive X-ray spectroscopy analyses. They crystallize with the tetragonal Ti(3)Co(5)B(2) structure type in space group P4/mbm (No. 127). Tetragonal prisms of Ru/Ir atoms are filled with titanium in the boron-poorest phase (Ti(3)Ru(2.9)Ir(2.1)B(2)). Gradual substitution of titanium by boron then results in the successive filling of this site by a Ti/B mixture en route to the complete boron occupation, leading to the boron-richest phase (Ti(2)Ru(2.8)Ir(2.2)B(3)). Furthermore, both ruthenium and iridium share two sites in these structures, but a clear Ru/Ir site preference is found. First-principles density functional theory calculations (Vienna ab initio simulation package) on appropriate structural models (using a supercell approach) have provided more evidence on the stability of the boron-richest and -poorest phases, and the calculated lattice parameters corroborate very well with the experimentally found ones. Linear muffin-tin orbital atomic sphere approximation calculations further supported these findings through crystal orbital Hamilton population bonding analyses, which also show that the Ru/Ir-B and Ru/Ir-Ti heteroatomic interactions are mainly responsible for the structural stability of these compounds. Furthermore, some stable and unstable phases of this complex series could be predicted using the rigid-band model. According to the density of states analyses, all phases should be metallic conductors, as was expected from these metal-rich borides.     

Vapour pressure of 4-methylpyridine (MePy) over [Ni(MePy)4(NCS)2]·y(MePy) and [Cu(MePy)4(NCS)2]·2/3(MePy) clathrates during their dissociation

Strain measurement and quasiequilibrium thermogravimetry were used to study the dissociation processes of two clathrates, [Ni(MePy)₄(NCS)₂]·(MePy) and [Cu(MePy)₄(NCS)₂]·2/3(MePy), accompanied by the liberation of MePy into the gaseous phase. In the Ni clathrate dissociation process in the temperature range 298–368 K the liberated MePy was redistributed between the solid clathrate and gaseous phases; the MePy vapour pressure over the clathrate is a function of temperature and the guest contenty, which agrees with the presence in the MePy-[Ni(MePy)₄(NCS)₂] system of a wide range of -clathrate solutions, [Ni(MePy)₄(NCS)₂]·y(MePy). The same methods used to study the Cu clathrate dissociation resulted in conclusions different from those obtained for the dissociation process of the above clathrate: the process is described by the equation [Cu(MePy)₄(NCS)₂]·2/3(MePy)_solid =[Cu(MePy)₂(NCS)₂]_solid+22/3(MePy)_gas; the temperature dependence of the Mepy vapour pressure over the solid sample does not depend on its composition, which points to the absence from the system of solid solutions based on the clathrate. Standard changes of the enthalpy, entropy, and isobaric-isothermal reaction potential for the temperature range 292–325 K are equal to 178.6±1.7 kJ (mole of clathrate)^–1, 463±5.6 J (mole of clathrate)^–1 K^–1, and 40.4±2.4 kJ (mole of clathrate)^–1, respectively.     

Synthesis, crystal structure, and physical properties of the type-I clathrate Ba(8-δ)Ni(x)□(y)Si(46-x-y)

Type-I clathrate phase Ba(8)Ni(x)□(y)Si(46-x-y) (□ = vacancy) was obtained from the elements at 1000 °C with the homogeneity range 2.4 ≤ x ≤ 3.8 and 0 ≤ y ≤ 0.9. In addition, samples with low Ni content (x = 1.4 and 1.6; y = 0) and small Ba deficiency were prepared from the melt by steel-quenching. Compositions were established by microprobe analysis and crystal structure determination. Ba(8-δ)Ni(x)□(y)Si(46-x-y) crystallizes in the space group Pm ?3n (No. 223) with lattice parameter ranging from a = 10.3088(1) ? for Ba(7.9(1))Ni(1.4(1))Si(44.6(1)) to a = 10.2896(1) ? for Ba(8.00(3))Ni(3.82(4))Si(41.33(6)). Single-crystal X-ray diffraction data together with microprobe analysis indicate an increasing number of framework vacancies toward compositions with higher Ni content. For all compositions investigated, Ni K-edge X-ray absorption spectroscopy measurements showed an electronic state close to that of elemental Ni. All samples exhibit metallic-like behavior with moderate thermopower and low thermal conductivity in the temperature range 300-773 K. Samples with compositions Ba(7.9(1))Ni(1.4(1))Si(44.6(1)) and Ba(7.9(1))Ni(1.6(1))Si(44.4(1)) are superconducting with T(c) values of 6.0 and 5.5 K, respectively.     

Syntheses and characterization of Zn(II), Cd(II) and Hg(II) complexes with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP y P z CA) ligand

From the reaction between Zn(II), Cd(II) and Hg(II) with 5-methyl-1-(2′-pyridyl)pyrazole-3-carboxamide (MP _y P _z CA) in ethanol, the complexes [Zn(MP _y P _z CA)₂(NO₃)]⁺ [(NO₃)_0.60(ClO₄)_0.40]^?·H₂O, Cd(MP _y P _z CA)₂Cl₂ and Hg(MP _y P _z CA)(SCN)₂ were obtained. These compounds have been characterized by IR and CHN analyses. The structure of [Zn(MP _y P _z CA)₂NO₃]⁺[(NO₃)_0.60(ClO₄)_0.40]^?·H₂O has been solved by X-ray crystallography. The coordination environment around the Zn(II) may be described as a trigonal bipyramid in which the ligands are both bidentate, but coordinated differently. The coordination sphere is completed with the oxygen atom of a nitrate anion as a unidentate ligand.     

Synthesis of Ru(0.58)In(0.42)O(y)⋅nH(2)O nanoparticles dispersed onto poly(sodium-4-styrene sulfonate)-functionalized multi-walled carbon nanotubes and their application for electrochemical capacitors

In this work, poly(sodium-4-styrene sulfonate) (PSS)-functionalized multi-walled carbon nanotubes (FMWCNTs) were first synthesized via a polymer-assisted technique. Then, Ru(0.58)In(0.42)O(y)?nH(2)O nanoparticles (NPs) were mono-dispersed onto the FMWCNTs surfaces under mild hydrothermal condition. Here, PSS with negative charge serves as a bifunctional molecule both for solubilizing and dispersing MWCNTs into aqueous solution and for tethering Ru(3+) and In(3+) to facilitate the good dispersion of Ru(1-)(x)In(x)O(y)?nH(2)O NPs onto their surfaces. The good dispersion of Ru(0.58)In(0.42)O(y)?nH(2)O NPs onto FMWCNTs makes OH(-) ions and electrons easily contact these NPs with abundant electroactive sites, which results in a large specific capacitance (SC) of 319Fg(-1) for the naocomposites. Moreover, a symmetric electrochemical capacitor (EC) is constructed by using the nanocomposites as electrodes and delivers large specific energy density of 18.1Whkg(-1), desirable power property of 1302Wkg(-1), high electrochemical reversibility and good SC retention of 84.7%.     

Molybdenum oxides versus molybdenum sulfides: geometric and electronic structures of Mo₃X(y)⁻ (X = O, S and y = 6, 9) clusters

We have conducted a comparative computational investigation of the molecular structure and water adsorption properties of molybdenum oxide and sulfide clusters using density functional theory methods. We have found that while Mo?O?? and Mo?S?? assume very similar ring-type isomers, Mo?O?? and Mo?S?? clusters are very different with Mo?O?? having a ring-type structure and Mo?S?? having a more open, linear-type geometry. The more rigid ∠(Mo-S-Mo) bond angle is the primary geometric property responsible for producing such different lowest energy isomers. By computing molecular complexation energies, it is observed that water is found to adsorb more strongly to Mo?O?? than to Mo?S??, due to a stronger oxide-water hydrogen bond, although dispersion effects reduce this difference when molybdenum centers contribute to the binding. Investigating the energetics of dissociative water addition to Mo?X?? clusters, we find that, while the oxide cluster shows kinetic site-selectivity (bridging position vs terminal position), the sulfide cluster exhibits thermodynamic site-selectivity.