Comparative energies of Zn(II) cation localization as a function of the distance between two forming cation position aluminium ions in high-silica zeolites

Periodical calculations of Zn(II) metal cation stabilization in cationic positions with distantly placed aluminium ions has been performed for high-silica ferrierite. It was found that decrease of the stabilization energy at large distances between Al ions (more than 10 Å) is about of 2 eV in comparison with nearest possible position of two Al ions in the zeolite lattice and weekly depended on following increase of the Al-Al distance. Main changes in stabilization energy occured within a 3-Å interval of these distances. Only for the localizations of both Al ions in one zeolite ring zinc cationic form is more stable than hydrogen form.     

Theoretical analysis of dissociative adsorption of H2O on Ni(100)

In conclusion, let us note the principal results of the calculation.

Theoretical analysis of magnetic and electric hyperfine interactions on 1H and 2H nuclei of bis(acetylacetonato) copper (II)

The INDO method has been used in calculating the tensors of hyperfine structure and the electric field gradient on the ¹H and ²H nuclei in Cu(acac)₂. The procedure used in calculating the magnetic resonance parameters (MRPs) is based on an accounting for one-center and two-center Coulomb integrals of dipole-dipole interaction. The influence of out-of-plane step distortion of the complex on the MRPs is examined critically.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 149–155, March–April, 1988.The authors wish to express their appreciation to P. V. Schastnev and S. A. Mustafaev for valuable discussion and for assistance in the work.     

Nonempirical calculations of water adsorption on bridged structural fragments of aluminosilicate

Within the discussion of the possibility to apply semiempirical methods for chemisorption calculations, nonempirical calculations of two types of adsorption complexes of H₂O molecule with bridged structural fragments of aluminosilicate have been carried out.

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Theoretical and Experimental Studies of the Nature of the Catalytic Activity of VO x /TiO2 Systems

The states of supported vanadium and the nature of activation of ammonia adsorbed on vanadium sites of V _x /Ti₂ catalysts are studied by ⁵¹V NMR spectroscopy and diffuse-reflectance IR Fourier-transform (DRIFT) spectroscopy using cluster quantum chemical calculations of N₃ adsorption. We employ the V _x /Ti₂ catalyst of two types: the monolayer catalyst in which vanadium is located on the surface of well-crystallized anatase and the catalyst in which vanadium embedded in the anatase lattice at a rather great depth. It is shown that ammonia is predominantly adsorbed on Lewis acid sites of the monolayer catalyst, whereas most of N₃ adsorbed on the catalyst containing bulk vanadium is in the form of ammonium ions. Analysis of experimental and calculated data suggests that, in the monolayer catalyst, N₃ molecules in the selective reduction of nitrogen oxides are activated on Lewis acid sites. Ammonia activation involves the dissociation of the N–H bond in a coordinated molecule, which results in the formation of the amide V–N₂ group and a water molecule coordinated by a V⁵⁺ ion. It is likely that, in the case of the catalyst containing bulk vanadium, this reaction occurs with the predominant participation of ammonium ions.