Effects of Hf and W doping on the commensurate charge density waves in 1T-TaS2

The electrical resistivities of Hf-doped and W-doped 1T-TaS₂ have been measured to investigate the influence of varying the Fermi level on the formation of commensurate charge density waves. It was found that W-doping is far more effective in breaking the C-CDW phase than Hf-doping. Such results are explained by the energy consideration of the system with the Hubbard gap which is produced by the Mott-localization.     

Ternary liquid—liquid equilibria: The associated solution theory

The capabilities of the associated solution theory in correlating ternary liquid—liquid phase equilibria from binary data have been examined. It is shown that the theory is capable of quantitatively good correlation of data for the four systems studied.     

Semi-empirical molecular orbital calculations the electronic structure and the spin-orbit coupling in azabenzenes

Electronic structures of pyridine, pyrazine, pyrimidine and pyridazine are studied by a semiempirical SCF method for valence electron systems previously proposed by the present authors. The charge distributions, transition energies and oscillator strengths of these compounds are calculated. The calculated results show fairly good agreement with the observed ones. Using these results, we have further calculated the oscillator strengths of singlet-triplet transitions and the life times of the triplet states (). In this treatment, we have considered the mixing of various singlets with T ₁ and triplets with S ₀, and the effect of -electrons is studied.

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Zusammenfassung Es werden nach einer von den Autoren dieser Arbeit vorgeschlagenen Methode die Elektronenstrukturen von Pyridin, Pyrazin, Pyrimidin und Pyridazin studiert. Die halbempirische SCF-Methode für Valenzelektronensysteme gestattet die Berechnung der Ladungsverteilungen, Übergangsenergien und Oszillatorstärken, die in recht guter Übereinstimmung mit der Beobachtung stehen. Ferner werden die Oszillatorstärken von Singulett-Triplett-Übergängen und die Lebensdauer von Triplett-Zuständen () berechnet.

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Résumé Les structures électroniques de la pyridine, de la pyrazine, de la pyrimidine et de la pyridazine sont étudiées par une méthode SCF semiempirique pour les électrons de valence proposée précédemment par les auteurs. Les distributions de charge, les énergies de transition et les forces oscillatrices de ces composés sont calculées, donnant des résultats en bon accord avec l'expérience. De plus nous avons calculé les forces oscillatrices des transitions singulet-triplet et les durées de vie des états triplets (). Dans ce calcul nous avons inclus l'interaction de configuration et l'étude de l'effet des électrons .

     

Locating subsets of a Hilbert space

This paper deals with locatedness of convex subsets in inner product and Hilbert spaces which plays a crucial role in the constructive validity of many important theorems of analysis.

     

Rate constants of the reaction of ozone with trans-1,2-dichloroethene and vinyl chloride in air

Kinetic studies on reactions of ozone with trans-1,2-dichloroethene (DCE) and vinyl chloride (VC) were performed in air. In the presence of scavengers of radicals, such as CH₃CHO, the rates for both reactions are second order (first order in each reactant). Observed rate constants are (1.80 ± 0.29) X 10^?19 cm³/molecule·s for DCE and (2.45 ± 0.45) × 10^?19 cm³/molecule·s for VC. In the presence of CH₃CHO, propene ozonide \documentclass{article}\pagestyle{empty}\begin{document}$ ({\rm CH}_3 \overline {{\rm CHOOCH}_2 {\rm O}}) $\end{document} was observed as a product in the case of VC. Peroxyformic acid (HC)O(OOH) was detected in both reactions. The Criegee mechanism was proposed to play a major role in the reaction of ozone with chloroolefins. The branching ratio of O₃ + CH₂=CHCl → CH₂OO + HCOCl (6a), CHClOO + HCHO (6b) was obtained as 76:24, and the fraction of the stabilized CH₂OO was estimated to be 0.25 of that produced in reaction (6a).     

Photoenhancement of the nitrous acid formation in the surface reaction of nitrogen dioxide and water vapor: Extra radical source in smog chamber experiments

The surface reaction of NO₂ and H₂O vapor to emit HONO into the gas phase was studied in the evacuable and bakeable photochemical chamber under the irradiation of UV-visible light (? 290 nm). Kinetic analysis of the NO, NO₂, and HONO with the aid of computer modeling strongly suggested that the formation of HONO by the surface reaction is photoenhanced. When a linear regression was assumed, the photoenhancement factor defined by {(k′₂₁/k₂₁) ? 1} was expressed as (6.8 ± 2.5)k₁ under our experimental conditions, where k₁ is the primary photolysis rate of NO₂, and k₂₁, k′₂₁ are the second-order-equivalent rate constants of the HONO formation reaction in dark and under irradiation, respectively. The discussion was made that this photocatalitic enhancement of HONO formation would explain the nature of the extra OH radical flux in the smog chamber experiments, which has been discussed as “unknown radical source” and has still been unexplained by the surface dark reaction of NO₂ and H₂O to emit HONO.     

Products and mechanism for the OH radical initiated oxidation of acrylonitrile,methacrylonitrile, and allylcyanide in the presence of NO

The photooxidation of acrylonitrile, methacylonitrile, and allylcyanide in the presence of NO was studied in parts per million concentration using the long-path Fourier transform IR spectroscopic method. The stoichiometry of the OH radical initiated oxidation of methacrylonitrile was established as \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {{\rm OH}} \right) + {\rm CH}_{\rm 2} = {\rm C}\left( {{\rm CH}_{\rm 3} } \right){\rm CN + 2NO + 2O}_{\rm 2} \mathop {\hbox to 20pt{\rightarrowfill}}\limits^{1.0} {\rm HCHO + CH}_{\rm 3} {\rm COCN + 2NO}_{{\rm 2}} + \left( {{\rm OH}} \right) $\end{document}. The yield of HCHO for acrylonitrile and allylcyanide was found to be ca. 100 and 80%, and the stoichiometric reactions were assessed to proceed, \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {{\rm OH}} \right) + {\rm CH}_{\rm 2} = {\rm CHCN + 2NO + 2O}_{\rm 2} \mathop {\hbox to 20pt{\rightarrowfill}}\limits^{1.0} {\rm HCHO + HCOCN + 2NO}_{\rm 2} + \left( {{\rm OH}} \right) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \left( {{\rm OH}} \right) + {\rm CH}_{\rm 2} = {\rm CHCH}_{\rm 2} {\rm CN + 2NO + 2O}_{\rm 2} \mathop {\hbox to 20pt{\rightarrowfill}}\limits^{0.8} {\rm HCHO + HCOCH}{\rm 2} {\rm CN + 2NO}_{\rm 2} + \left( {{\rm OH}} \right) $\end{document}, respectively. These results revealed that the reaction mechanism for these unsaturated organic cyanides are analogous to that of olefins.     

Regioselective hydrophenylation of olefins catalyzed by an Ir(III) complex

The novel, anti-Markovnikov, arylation of olefins with benzene to produce straight-chain alkylbenzenes with higher selectivity than branched alkylbenzenes is catalyzed by [Ir(μ-acac-O,O′,C³)(acac-O,O′)(acac-C³)]₂ (acac=acetylacetonato), 1 [J. Am. Chem. Soc. 122 (2000) 7414]. The reaction of benzene with propylene gave n-propylbenzene and cumene in 61 and 39% selectivities, respectively. The reaction of benzene and styrene afforded 1,2-diphenylethane in 98% selectivity. Considering the anti-Markovnikov regioselectivity and lack of inhibition by water, we propose that the reaction does not proceed via a Friedel–Crafts, carbocation, mechanism. Complex 1, amongst the various transition metal complexes examined, is the most efficient for catalyzing the anti-Markovnikov olefin arylation. The crystal structure of complex 1 was solved and is consistent with a binuclear Ir(III) structure with three different types of coordinated acac ligands as reported by earlier solution IR and NMR analyses. [Ir(μ-acac-O,O′,C³)(acac-O,O′)Cl]₂, 2, was prepared by the reaction of complex 1 with benzoyl chloride, and the crystal structure was also reported.