Many-body theory of the Auger Auger-electron coincidence spectroscopy (AAECS) spectra of solids

A pair of Auger electrons generated, respectively, by creation and annihilation of the same multiple-hole state can be collected in coincidence by Auger Auger-electron coincidence spectroscopy (AAECS). In the present paper a many-body theory of AAECS spectra generated by Auger cascade decays in which the lifetime of a core-hole acts as an internal clock for the screening mechanism is formulated by treating photoelectrons and Auger electrons on the same footing. The unexploited basic spectral features of AAECS spectra of solids are elucidated by the present theory to show how the core-hole screening (delocalization of a valence hole) will affect the coincidence spectral lineshape.     

Density-functional study for the NOx (x = 1, 2) dissociation mechanism on the Cu(1 1 1) surface

Spin-polarized density functional theory calculation is employed to study the adsorption and dissociation of NO₂ molecule on Cu(1 1 1) surface. It is shown that the most favorable adsorption structure is the NO₂ (T,T-O-,O′-nitrito) configuration which has an adsorption energy of −1.49 eV. The barriers for step-wise NO₂ dissociation reaction, NO_2(g) → N_(a) + 2O_(a), are 1.05 (for O–N–O bond activation), and 2.08 eV (for N–O bond activation), respectively, and the entire process is 0.6 eV exothermic. The energetics of single N–O dissociation with and without the presence of N atom or O atom on the surface are also calculated. The results indicate that in the presence of O atom on Cu(1 1 1) surface would raise the N–O dissociation barrier, whereas in the presence of N atom decrease it. The interaction nature between adsorbates and substrate is analyzed by the local density of states (LDOS) calculation.     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Selective electronalysis of peracetic acid in the presence of a large excess of H2O2 at Au(1 1 1)-like gold electrode

Peracetic acid (PAA) has been selectively electroanalyzed in the presence of a large excess of hydrogen peroxide (H₂O₂), about 500 fold that of PAA, using Au (1 1 1)-like gold electrode in acetate buffer solutions of pH 5.4. Au(1 1 1)-like gold electrode was prepared by a controlled reductive desorption of a previously assembled thiol, typically cysteine, monolayer onto the polycrystalline gold (poly-Au) electrode. Cysteine molecules were selectively removed from the Au(1 1 1) facets of the poly-Au electrode, keeping the other two facets (i.e., Au(1 1 0) and Au(1 0 0)) under the protection of the adsorbed cysteine. It has been found that Au(1 1 1)-like gold electrode positively shifts the reduction peak of PAA, while, fortunately, shifts the reduction peak of H₂O₂ negatively, achieving a large potential separation (around 750 mV) between the two reduction peaks as compared with that (around 450 mV) obtained at the poly-Au electrode. This large potential separation between the two reduction peaks enabled the analysis of PAA in the presence of a large excess of H₂O₂. In addition, the positive shift of the reduction peak of PAA gives the present method a high immunity against the interference of the dissolved oxygen.     

水对甲醇在Rutile-TiO2(110)-(1 ×1)表面光催化解离的影响简

采用程序升温脱附方法研究了甲醇分子吸附在真空退火后的二氧化钛（110）表面的光催化过程,对比分析了单独吸附甲醇分子以及甲醇分子与水分子共吸附情况下的光催化解离过程. 结果表明,在二氧化钛（110）表面吸附的甲醇分子对共吸附水分子的光催化解离过程并没有直接的帮助作用. 共吸附状态下的水分子也同样没有影响到甲醇的光致解离过程,但是水分子的存在抑制了甲醇光解产物甲醛的光致脱附过程,同时促进了甲酸甲酯的形成.     

First-principles study of the electronic and magnetic properties of oxygen-deficient rutile TiO2(1 1 0) surface

Based on first-principles electronic structure calculations we find that the bridging oxygen vacancies on the (1 1 0) surface is more favorable and may be responsible for the unexpected ferromagnetism in undoped rutile TiO₂. Our results show that the ferromagnetism largely originates from the d orbitals of low-charge-state Ti ions converted from Ti⁴⁺ ions induced by the surface oxygen vacancies. The second-nearest neighbors of these ions (fivefold coordinated Ti) also contribute to the total magnetic moments. The spins induced by the local oxygen vacancies form a ferromagnetic arrangement.     

Quantum chemistry studies on the Ru-M interactions and the P NMR in [Ru(CO)3(Ph2Ppy)2(MCl2)] (M = Zn, Cd, Hg)

To study the Ru-M interactions and their effects on ³¹P NMR, complexes [Ru(CO)₃(Ph₂Ppy)₂] (py = pyridine) (1) and [Ru(CO)₃(Ph₂Ppy)₂MCl₂] (M = Zn, 2; Cd, 3; Hg, 4) were calculated by density functional theory (DFT) PBE0 method. Moreover, the PBE0-GIAO method was employed to calculate the ³¹P chemical shifts in complexes. The calculated ³¹P chemical shifts in 1-3 follow 2 > 3 > 1 which are consistent to experimental results, proving that PBE0-GIAO method adopted in this study is reasonable. This method is employed to predict the ³¹P chemical shift in designed complex 4. Compared with 1, the ³¹P chemical shifts in 2-4 vary resulting from adjacent Ru-M interactions. The Ru → M or Ru ← M charge-transfer interactions in 2-4 are revealed by second-order perturbation theory. The strength order of Ru → M interactions is the same as that of the P-Ru → M delocalization with Zn > Cd > Hg, which coincides with the order of ³¹P NMR chemical shifts. The interaction of Ru → M, corresponding to the delocalization from 4d orbital of Ru to s valence orbital of M²⁺, results in the delocalization of P-Ru → M, which decreases the electron density of P nucleus and causes the downfield ³¹P chemical shifts. Except 2, the back-donation effect of Ru ← M, arising from the delocalization from s valence orbital of M²⁺ to the valence orbital of Ru, is against the P-Ru → M delocalization and results in the upfield ³¹P chemical shifts in 4. Meanwhile, the binding energies indicate that complex 4 is stable and can be synthesized experimentally. However, as complex [Ru(CO)₃(Ph₂Ppy)₂HgCl]⁺5 is more stable than 4, the reaction of 1 with HgCl₂ only gave 5 experimentally.     

Argon matrix effect on the geometry and infrared spectrum of H2CMH2 (M = Ti, Zr, Hf): A theoretical study

Within the framework of polarizable continuum model with integral equation formalism (IEF-PCM), an argon matrix effect on the geometry and infrared frequencies of the agostic H₂CMH₂ (M = Ti, Zr, Hf) methylidene complexes was investigated at B3LYP level of theory with the 6-311++G(3df,3pd) basis set for C, H, and Ti atoms and Stuttgart/Dresden ECPs MWB28 and MWB60 for the Zr and Hf atoms. At the B3LYP/IEF-PCM level of theory, H₂CTiH₂ was optimized to an energy minimum having a pyramidal structure. The calculated dipole moment of this structure is 3.06 D. The B3LYP/IEF-PCM simulations gave the three complexes’ agostic angle ∠HCM (°), distance r(H?M) (Å), and CM bond length r(CM) (Å) as follows: ∠HCTi = 87.4, r(H?Ti) = 2.079, r(CTi) = 1.803; ∠HCZr = 89.3, r(H?Zr) = 2.243, r(CZr) = 1.956; ∠HCHf = 94.7, r(H?Hf) = 2.343, r(CHf) = 1.972. As a comparison, the B3LYP simulations gave the values as follows: ∠HCTi = 91.5, r(H?Ti) = 2.150, r(CTi) = 1.811; ∠HCZr = 92.9, r(H?Zr) = 2.299, r(CZr) = 1.955; ∠HCHf = 95.6, r(H?Hf) = 2.352, r(CHf) = 1.967. As far as the MH₂ symmetric and asymmetric stretching and CH₂ wagging frequencies are concerned, the IEF-PCM calculated values are in better agreement with the experimental argon matrix ones than those calculated based on a gas phase model.     

Theoretical investigation on H2 elimination reactions of germylenoid H2GeLiF with RH (R = F, OH, and NH2)

The H₂ elimination reactions of the germylenoid H₂GeLiF with RH (R = F, OH, NH₂) have been studied by using the DFT B3LYP and QCISD methods. The calculated results indicate that all the mechanisms of the three reactions are identical to each other and under the same condition the H₂ elimination reactions should occur easily in the order of H-F > H-OH > H-NH₂. In THF solvent the H₂ elimination reactions get more difficult than in gas phase. Compared with the insertion reactions of H₂GeLiF with RH (R = F, OH, NH₂), the H₂ elimination reactions have the lower activation barriers and should be more favorable.     

The S1 ← S0 0–0 transition energies of polychlorinated dibenzofurans (PCDFs) revisited: CIS(D) and MP2 calculations with correction for correlation energies

This paper reexamines the structures and energies of dibenzofuran and twenty PCDFs in S₁–S₃ states. It was demonstrated that, although the CIS method gives a false relative ordering of excited states, the false ordering can be remedied by the CIS(D) method. Moreover the CIS geometries of typical PCDF molecules reasonably agree with their SAC-CI geometries. It was found that molecules chlorinated at the 1- and 9-positions are twisted in the S₂ state but are planar in other states, except for 1,4,6,9-TeCDF and fully chlorinated dibenzofuran (OCDF). The twisted structure of 1,4,6,9-TeCDF occurs in the S₃ state, but the structure of OCDF is twisted in every state. We partitioned the molecule into the parent structure and four chlorine groups and measured the twist energy with reference to the ground state. Then, the S_i ← S₀ 0–0 transition energies (i = 1, 2) calculated using the CIS(D) and MP2 methods could be expressed as a multiple linear equation with components and twist energy. It was further confirmed that if the multiple linear equation is corrected for residual correlation energies of the parent structure, it can predict the S₁ ← S₀ 0–0 transition energies with high precision.     

(Vapor + liquid) equilibria of the binary mixtures of m-cresol with C1-C4 aliphatic alcohols at 95.5 kPa

Bubble point temperatures at 95.5 kPa, over the entire composition range, are measured for the binary mixtures formed by m-cresol with: methanol, ethanol, 1-propanol, 2-propanol, and n-, iso-, sec-, and tert-butanols - using a Swietoslawski-type ebulliometer. The liquid phase composition - bubble point temperature measurements are well represented by the Wilson model. (Vapor + liquid) equilibria predicted from the model are presented.     

(p, ρ, T) properties, and apparent molar volumes V? of ZnBr2 in methanol at T = (298.15 to 398.15) K and pressures up to p = 40 MPa

The (p, ρ, T) properties of pure methanol, the (p, ρ, T) properties and apparent molar volumes V_? of ZnBr₂ in methanol at T = (298.15 to 398.15) K and pressures up to p = 40 MPa are reported, and apparent molar volumes have been evaluated. The experimental (p, ρ, T, m) values were described by an equation of state. For the solutions the experiments were carried out at molalities m = (0.05772, 0.37852, 0.71585 and 1.95061) mol · kg⁻¹ of zinc bromide.     

Vapor–liquid equilibria of the carbon dioxide (CO2) + 2,2-dichloro-1,1,1-trifluoroethane (R123) system and carbon dioxide (CO2) + 1-chloro-1,2,2,2-tetrafluoroethane (R124) system

Binary vapor–liquid equilibrium data were measured for the carbon dioxide (CO₂) + 2,2-dichloro-1,1,1-trifluoroethane (R123) system and the carbon dioxide (CO₂) + 1-chloro-1,2,2,2-tetrafluoroethane (R124) system at temperature from 313.15 to 333.15 K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by Peng–Robinson equation of state using the Wong–Sandler mixing rules.     

TPD study of NH3 adsorption/desorption on the surface of V/Ti, V/Al based catalysts for selective catalytic reduction of NOx by ammonia 1. TPD test of γ-Al2O3, TiO2 (anatase) and alumina-supported vanadia catalysts

The effect of temperature on the adsorption/desorption of ammonia from the air mixture on the surface of γ-Al₂O₃, TiO₂ (anatase) and alumina-supported vanadia catalyst samples has been investigated using temperature-programmed desorption (TPD). When the vanadia loading was increased, the fraction of the acid sites providing the NH₃ adsorption in the high-temperature state decreased. At the same time, the fraction of the medium temperature state significantly increased.     

Novel M(II)–Hg(II) coordination polymers generated from metal-containing building blocks M(2-pyrazinecarboxylate)2 · (H2O)2 (M=Cu, Ni, Co) and HgCl2

A new class of M(II)–Hg(II) (M=Cu(II), Co(II), Ni(II)) mixed-metal coordination polymers, Cu(2-pyrazinecarboxylate)₂HgCl₂ (4), [Co(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.61H₂O (5) and [Ni(2-pyrazinecarboxylate)₂(HgCl₂)₂] · 0.77H₂O (6), have been prepared by self assembly of metal-containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂(M=Cu(II), Co(II), Ni(II)), with HgCl₂. Compounds 4–6 were characterized fully by IR, elemental analysis and single crystal X-ray diffraction. Compound 4 crystallized in the monoclinic space group C2/c, with a=17.916(5) Å, b=7.223(2) Å, c=13.335(4) Å, β=128.726(3)°, V=1346.2(6) ų, Z=4. It contains alternating Hg(II) and Cu(II) metal centers that are cross-linked by 2-pyrazinecarboxylate spacers and chlorine co-ligands to generate a unique three-dimensional Hg(II)–Cu(II) mixed metal framework. Compound 5 crystallized in the triclinic space group P , with a=6.3879(7) Å, b=6.6626(8) Å, c=13.2286(15) Å, α=96.339(2)°, β=91.590(2)°, γ=113.462(2)°, V=511.71(10) ų, Z=1. Compound 6 also crystallized in the triclinic space group P , with a=6.3543(8) Å, b=6.6194(8) Å, c=13.2801(16) Å, α=96.449(2)°, β=92.263(2)°, γ=113.541(2)°, V=506.67(11) ų, Z=1. Compounds 5 and 6 are isostructural and in the solid state the Hg(II)M(II)Hg(II) units are connected by Hg₂Cl₂ linkages to produce a novel M(II)–Hg(II) (M=Co(II), Ni(II)) zigzag mixed-metal chain, in which a new type of M–M′–M′–M array was observed. The metal containing building blocks, M(2-pyrazinecarboxylate)₂ · (H₂O)₂ (M=Cu(II), Co(II), Ni(II)), exhibit different connectivities to HgCl₂ depending on the metal cation contained within them.     

Characterization of Au-Rh and Au-Mo bimetallic nanoclusters on TiO2(110): A comparative study

Gold-rhodium and gold-molybdenum layers were prepared on a nearly stoichiometric titania and characterized by LEIS, XPS and STM. In the Au-Rh bimetallic system, Rh atoms impinged onto Au clusters pregrown on TiO₂(110) became covered by gold atoms. In contrast, Mo caused the disruption of gold nanoparticles.     

Vapour pressure and excess Gibbs free energy of the ternary system {x1CH3F + x2HCl + x3N2O} at temperature of 182.33 K

The equilibrium pressure of ternary mixtures of {x₁CH₃F + x₂HCl + x₃N₂O} covering the entire composition range has been measured at temperature of 182.33 K by the static method. The system exhibits a minimum pressure for the binary {x₁CH₃F + x₂HCl}. The molar excess Gibbs free energy has been calculated from the experimental equilibrium pressure. For the equimolar mixture . The (p, x, y) surface for the ternary system and the corresponding curves for the three constituent binary mixtures obtained from the Peng-Robinson equation of state are in agreement with the experimental data.     

Optimisation and validation of programmed temperature vaporization (PTV) injection in solvent vent mode for the analysis of the 15 + 1 EU-priority PAHs by GC-MS

This paper presents the optimisation of a programmed temperature vaporization solvent vent (PTV-SV) injection gas chromatographic mass spectrometric (GC-MS) method for the analysis of the 15 + 1 EU-priority PAHs in food extracts. Three operation parameters (vent time, vent flow and vent pressure) were optimised by applying a D-optimal experimental design. Among these variables, vent time showed the highest effect on the analytical response (signal intensity) of the target PAHs.The 15 + 1 EU-priority PAHs were analysed in solvent solutions and in extracts of fortified sausage. In addition, blank lamb meat extracts were prepared and spiked with the target PAHs prior to GC-MS analysis. The performance of the optimised PTV-SV injection GC-MS method was scrutinised for linearity, precision, matrix effects and robustness. All parameters were found satisfactorily. Compared to PTV injection in splitless mode, the PTV-SV injection method provided an enhancement of sensitivity for all target PAHs. Especially significant was the improvement of the S/N ratios of the compounds with the highest molecular mass.     

A convenient synthetic route to 2-aryl-N-tosylazetidines and their ZnX2 (X = I, OTf) mediated regioselective nucleophilic ring opening reactions: synthesis of γ-iodoamines and tetrahydropyrimidines

A general and convenient synthetic route to various 2-aryl-N-tosylazetidines has been described. Their ZnX₂ (X = I, OTf) mediated nucleophilic ring opening with halides and [4+2] cycloaddition reactions with various nitriles have been achieved to afford γ-iodoamines and substituted tetrahydropyrimidines, respectively, in good to excellent yields. A mechanism for the cycloaddition reaction is proposed.     

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine as models for metal-protein interactions: Synthesis and structural characterization. Crystal structure of Me2Sn(Tyr-Phe) · MeOH

New di- and triorganotin(IV) derivatives of tyrosinylphenylalanine (H₂Tyr-Phe) with general formulae R₂Sn(Tyr-Phe) where R = Me,n-Bu, n-Oct and Ph, and R₃^′Sn(HTyr-Phe) where R^′ = Me and Ph have been synthesized. The bonding and coordination behaviour in these derivatives are discussed on the basis of FT-IR, multinuclear ¹H, ¹³C and ¹¹⁹Sn NMR and ¹¹⁹Sn Mössbauer spectroscopic studies. These investigations suggest that dipeptide in R₂Sn(Tyr-Phe) acts as dianionic tridentate coordinating through −C(O)O⁻, -NH₂ and (-CO)N⁻_peptide groups while in case of R^′₃Sn(HTyr-Phe) the ligand acts as monoanionic bidentate coordinating through -C(O)O⁻ and -NH₂, and the polyhedron around tin in R₂Sn(Tyr-Phe) and R^′₃Sn(HTyr-Phe) is a distorted trigonal-bipyramidal. It is further confirmed by the single crystal X-ray structure of Me₂Sn(Tyr-Phe) · MeOH which shows two methyl groups and peptide nitrogen (N⁻_peptide) in the equatorial positions, while the two axial positions are occupied by the carboxylic oxygen (O⁻_carboxyl) and the amino nitrogen (N_amino) atom from the same ligand molecule. One methanol molecule is also present in the asymmetric unit.