Ab initio and density function theory studies on NLi6 molecule: compared with CLi6 and OLi6 species

A wide variety of geometrical structures of NLi₆ molecule were studied using HF ab initio and BLYP-DFT techniques. Three stationary configurations which take D_4h, D_3d and D_2d configurations were obtained. Their equilibrium geometries and fundamental frequencies were calculated at HF and BLYP-DFT levels. Among the three stable states, the global minimum prefers D_3d configuration, which is different from those of CLi₆ and OLi₆. The D_3d isomer of NLi₆ is 3.43 and 28.45 kcal/mol lower in energy than the D_4h and D_2d ones in the DFT calculation, respectively. All calculations were performed with 6-31G* polarized split-valence basis set.     

Configuration interaction calculation of the potential curves for the C3 molecule in its ground and lowest-lying Πu states

Ab initio SCF and Cl calculations are reported for the C₃ molecule using a basis set of double-zeta plus polarization quality. Potential curves are obtained for the symmetric stretch and bending and antisymmetric stretch vibrational coordinates for the ground and 3σ_u → l π_g^3,1Π_u excited states of this system in order to calculate the intensity distributions for the associated electronic transitions. The calculated T₀ value for the ¹Π_u ← X?¹ ∑⁺_g transition of 3.03 eV is in quite good agreement with the location of the origin of the 4050 Å (3.06 eV) band system in C₃, confirming its previous assignment to this electronic transition; the lifetime of the ¹H_u upper state is also obtained in the CI treatment. A value of 2.04 eV is calculated for the corresponding ³Π_u ← X?¹ ∑⁺_g origin, which result in turn suggests that the weak feature starting at 2.10 eV (5900 Å) should be assigned thereto.     

Vertical ionization potential of the CF2 radical

The CF₂ radical was generated in an equilibrium effusion cell by the reaction of gaseous SF₆ with carbon at 1550 K. From electron impact threshold measurements, the vertical IP of CF₂ was found to be 11.54 ± 0.10 eV. This value is lower than previous electron impact results, but it is consistent with data obtained from dissociative photoionization threshold measurements via a thermochemical cycle.     

The ionization potential of the BeH molecule

The ionization potential of the BeH molecule is derived from a few Rydberg states observed in the absorption spectrum and from “ab initio” calculations of the energies of the ground states of the BeH and BeH⁺ molecules at their equilibrium distances. The values are in agreement and yield PI(BeH, X²Σ⁺) = 66 100 ± 500 cm^?1.     

The vibration-rotation spectrum and anharmonic potential of H3

Some qualitative effects of anharmonicity on the spectra of H₃⁺ and D₃⁺ between low vibrational levels are described. Using large-basis vibration-rotation calculations with a Morse-based discrete variable representation for the vibrations and a symmetric-top basis for the rotations, new spectra of H₃⁺ and D₃⁺ have been assigned. This procedure was assisted by adjusting eight coefficients for H₃⁺ and six coefficients for D₃⁺ in the Meyer-Botschwina-Burton ab initio potential function, and eventually 621 new and old lines of H₃⁺ to levels up to 3ν₂ and 529 new and old lines of D₃⁺ to levels up to 2ν₂ have been fitted with standard deviations of 0.118 and 0.059 cm⁻¹, respectively. An attempt is made to compare five different potential energy functions for the H₃⁺ system, two ab initio and three adjusted to fit spectra of H₃⁺ or D₃⁺, by expanding them by the same procedure in the same variables. For extension of the present work to higher vibrational levels, more accurate boundary behaviour at linear configurations will be required, and some aspects of the use of hyperspherical coordinates are discussed.     

Thermoanalytical study of the systems PbCO3SrCO3 and PbCO3CaCO3

This study concerns the coprecipitation of the PbCO₃SrCO₃ and PbCO₃CaCO₃ systems in different molar relationships carried out under the same experimental conditions as the PbCO₃BaCO₃ system studied previously. The precipitates obtained were studied by chemical analysis, thermogravimetry, differential thermal analysis and X-ray powder diffraction. It has been established that, for the PbCO₃SrCO₃ system, solid solutions are obtained under all the different experimental conditions and for the PbCO₃CaCO₃ system the precipitates obtained are always mixtures of PbCO₃ and CaCO₃.     

Formation of WF−6 and its dissociative products by collisional ionization

The formation of negative ions in electron transfer reactions between hyperthermal alkali atoms (Na, K) and WF₆ has been studied in the energy range 0–30 eV c.m. Relative cross sections and translational energy thresholds for ion pair formation have been measured, from which the following electron affinities (EA) and bond dissociation energies (D) have been derived: EA(WF₆) = 3.7 eV, EA(WF₅) = 1.25 eV, D(WF₅—F) = 5.1 eV, D)WF₅—F^?) = 5.4 eV, D(WF^?₅—F) = 7.6 eV. Several ion molecule reactions are discussed which result in formation of secondary fragmentation ions and WF^?₇.     

Dissociation energy and ionization potential of the molecule CF

The gaseous equilibrium S + CF₂ = SF + CF was studied over the temperature range 1851 to 2232 K by mass spectrometry, and the derived enthalpy change was used to evaluate the heat of formation of CF ΔH₂₉₈ = 58.0 ± 2.4 kcal/mol (2.52 ± 0.10 eV), and the dissociation energy D₀⁰ (CF) = 130.8 ± 2.4 kcal/mol (5.67 ± 0.10 eV). The new thermochemical data indicate a slightly higher stability for CF than earlier determinations. Direct measurement by electron impact yielded a value of 9.17 ± 0.10 eV for the vertical ionization potential of CF, in agreement with an indirect result obtained from the photodissociative ionization of C₂F₄.     

Luminescence properties of efficient X-ray phosphors of YBa3B9O18, LuBa3(BO3)3, α-YBa3(BO3)3 and LuBO3

The samples of YBa₃B₉O₁₈, LuBa₃(BO₃)₃, α-YBa₃(BO₃)₃ and LuBO₃ powders have been synthesized by the solid-state reaction methods at high temperature and their X-ray excited luminescent properties were investigated. All the studied materials show a broad emission band in the wavelength range of 300-550 nm with the peak centers at about 385 nm for YBa₃B₉O₁₈ and LuBa₃(BO₃)₃, 415 nm for α-YBa₃(BO₃)₃ and 360 nm for LuBO₃ powders, respectively. Even though those compounds have the different atomic structures, they have the common structural feature of each yttrium or lutetium ion bonded to six separate BO₃ groups, i.e., octahedral RE(BO₃)₆ (RE=Lu or Y) moiety. This octahedral RE(BO₃)₆(RE=Lu or Y) moiety seems to be an important structural element for efficient X-ray excited luminescence of those compounds, as are the edge-sharing octahedral TaO₆ chains for tantalate emission.     

Multiphoton ionization of metal cluster complexes Os3(CO)12 and Ir4(CO)12: Determination of the ionization energy and coordination energy of the complex ions

Multiphoton ionization and the subsequent dissociation process of metal cluster complexes Os₃(CO)₁₂ and Ir₄(CO)₁₂, prepared in a supersonic jet, were studied by means of multiphoton ionization with time-of-flight (TOF) mass detection. The ionization energies of Os₃(CO)₁₂ and Ir₄(CO)₁₂ were determined to be 7.95 and 8.3 eV, respectively, from the laser wavelength at the ionization threshold. The coordination energies of Os₃(CO)₁₂⁺ and Ir₄(CO)₁₂⁺ ions were also determined to be 1.6 and 1.2 eV, respectively, from the excitation energy needed to cause the appearance of fragment ions. The observed values agreed reasonably well with the ones calculated by using the density functional theory method.     

The support and characterization of C60 and MoO3 on Al2O3

A new type of catalyst from supporting C₆₀ on MoO₃ and Al₂O₃ has been prepared. The effect of different order of impregnation and calcination atmosphere on catalyst are investigated by the solution test in toluene, UV-VIS spectroscopy and temperature programmed reduction (TPR). The results show that when the catalyst was prepared by supporting MoO₃ on C₆₀/Al₂O₃ and calcined in N₂, there is a stronger interaction between C₆₀, MoO₃ and Al₂O₃, but when supporting C₆₀ on MoO₃/Al₂O₃, the interaction is relatively weak. We consider that in the former method a new complex, Mo–C₆₀–O–Al, is formed.     

Theoretical study of the electronic transition moment for the d 3IIga 3IIu band system of the C2 molecule

Large scale ab initio SCF and CI calculations are employed to study the potential curves for the d ³II_g, a ³II_u and X¹Σ⁺_g states of the C₂ radical. The electronic transition moment R_e′e″ for the Swan bands (d ³II_ga ³II_u) is calculated in various AO and MO basis sets as a function of the internuclear CC distance. The form of the Σ|R_e′e″|² curve is in very good agreement with that obtained recently from measurements of Danylewych and Nicholls and Tatarczyk et al.; the calculated value for Σ|R_e′e″² at 2.44 bohr is found to be 5.2 au² compared to the most recent experimental values of |R_e(r_oo)|² = 3.57 au² of Tatarczyk et al.     

Ab initio investigations of structure and stability of the LiBeF3 molecule

Ab initio calculations of the potential energy surface of LiBeF₃ have been performed using the basis set of Roos and Siegbahn. The extremum and saddle points were made more precise with Huzinaga-Dunning basis sets in double-and triple-zeta contractions The “bidentate” structure (symmetry group C_2v) is found to have the lowest energy and is much more advantageous than the others, and the LiBeF₃ molecule turns out to be rigid with respect to migration of the cation around the anion. The calculated internuclear distances and the energy of complex formation are in agreement with experimental values within 0.03 Å and 2 kcal/mole. The results are compared with similar ab initio data for LiBeH₃ and LiNO₃.     

The calculation of the ionization energies of CrOCl3 by configuration-interaction and ΔSCF methods

The calculation of the valence ionization energies of CrOCl₃ by a configuration-interaction method is described and compared with the He(I) and He(II) photoelectron spectra of this molecule. Such a calculation yields ionization energies in good agreement with experiment and is superior to the ΔSCF method which predicts the incorrect ground state of CrOCl⁺₃.     

The structural interrelationship between the three polymorphs of Rh2O3 and Rh2S3, Rh2Se3, and Ir2S3

The syntheses of each of the three modifications of rhodium sesquioxide are reviewed and their infrared spectra are described. Models of each of these structures were constructed and manipulated using interactive molecular graphics. Their interrelationship is clearly described and used both to explain the similar features observed in their respective infrared spectra and to predict the occurrence of other discrete structures in the Rh₂O₃ system. Rhodium sesquisulfide, Rh₂S₃, is shown to be isostructural with the high pressure modification, II-Rh₂O₃.     

WO3/g-C3N4异质结催化剂的制备及其氧化脱硫性能

以尿素和钨酸铵为原料采用浸渍法制备了金属氧化物三氧化钨（WO₃）与石墨相氮化碳（g-C₃N₄）异质结复合材料WO₃/g-C₃N₄。采用XRD、UV-vis、SEM、PL和XPS表征手段考察了催化剂的理化性质,发现WO₃与g-C₃N₄存在较好的相互作用和电子转移,保证了WO₃/g-C₃N₄本身所具有较高的氧化脱硫活性。以WO₃/g-C₃N₄作为催化剂,过氧化氢异丙苯为氧化剂,考察其光催化氧化脱硫性能,在反应温度80℃,O/S物质的量比为3.0的反应条件下,反应180 min,二苯并噻吩（DBT）转化率可以达到72.79%。通过游离基捕获实验,发现超氧自由基（·O₂^-）、电子（e^-）、羟基自由基（·OH）起到了促进反应速率的作用,并对该体系的反应机理进行了探讨。     

Nonempirical SQM FF calculation of vibrational spectra for the acetonitrile molecule coordinated to Lewis acids BF3 and BCl3

In terms of SQM FF methods, nonempirical quantumchemical calculations of vibrational spectra for acetonitrile molecule coordinated to Lewis acids BF₃ and BCl₃ were carried out. Scaling factors were obtained from the conditions to reproduce vibrational spectra of CH₃CN and CD₃CN molecules. Contribution of the increase in the power force constant and the kinetic effect of the NB bond to the shift of _CN and _CC under coordination has been determined.

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SQM FF BF₃ BCl₃. CH₃CN CD₃CN. NB _{CN CC} .

     

The preparation and properties of BaTa0.8S3, BaNb0.8S3, and BaTa0.8Se3

Compounds of the formulas BaTa_0.8S₃, BaNb_0.8S₃, and BaTa_0.8Se₃ were prepared by two methods: reaction of the elements in evacuated silica tubes and reaction of H₂S over mixtures of BaCO₃ and 0.4Ta(Nb)₂O₅. They have the hexagonal BaNiO₃-type structure and are diamagnetic semiconductors. From the stoichiometries and properties we conclude that Nb and Ta are pentavalent.     

RbAuUSe3, CsAuUSe3, RbAuUTe3, and CsAuUTe3: Syntheses and structure; magnetic properties of RbAuUSe3

The compounds RbAuUSe₃, CsAuUSe₃, and RbAuUTe₃ were synthesized at 1073 K from the reactions of U, Au, Q, and A₂Q₃ (A=Rb or Cs; Q=Se or Te). The compound CsAuUTe₃ was synthesized at 1173 K from the reaction of U, Au, Te, and CsCl as a flux. These isostructural compounds crystallize in the KCuZrS₃ structure type in space group Cmcm of the orthorhombic system. The structure consists of layers that contain nearly regular UQ₆ octahedra and distorted AuQ₄ tetrahedra. The infinite layers are separated by bicapped trigonal prismatic A cations. The magnetic behavior of RbAuUSe₃ deviates significantly from Curie–Weiss behavior at low temperatures. For T>200 K, the values of the Curie constant C and the Weiss constant θ_p are 1.82(9) emu K mol⁻¹ and −3.5(2)×10² K, respectively. The effective magnetic moment μ_eff is 3.81(9) μ_B. Formal oxidation states of A/Au/U/Q may be assigned as +1/+1/+4/−2, respectively.     

The role of acidity of MoO3?SiO2 and WO3?SiO2 catalysts

The acidity of various MoO₃–SiO₂ and WO₃ catalysts has been measured by means of ammonia adsorption. Whereas the acidity of silica and pure metal oxides is very low, an increase of surface acidity results from a reaction between silica support and metal oxides. A significant correlation between surface acidity and catalytic activity for aromatization of lower olefines could be found.

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MoO₃–SiO₂ WO₃ . SiO₂ . , SiO₂ . .