Comparative Analysis of Hydrogen,van der Waals,and Halogen Bonds in Ammonia Complexes with HCl and ClF Molecules

Russian Journal of Physical Chemistry A - Quantum chemical calculations of molecular complexes formed by ammonia and methanide (electron pair donor) with HCl and ClF molecules (acceptor) at...     

Synthesis and characterization of tetraphenylphosphonium salts of N-phosphorylated thioureas and bis-thioureas

Russian Chemical Bulletin - Tetraphenylphosphonium salts of N-phosphorylated thioureas and bio-thioureas were synthesized by the reactions of their sodium salts with PPh4Br in 96% aqueous EtOH. The...     

Peculiarities of the Crystal Structure and Texture of Isotropic and Anisotropic Polycrystalline Hexagonal Ferrites BaFe12O19 Synthesized by Radiation-Thermal Sintering

Russian Microelectronics - In this work the crystal structure and texture of isotropic and anisotropic polycrystalline hexagonal ferrites BaFe12O19 obtained by the method of radiation-thermal...     

Ohmic Contacts to CVD Diamond with Boron-Doped Delta Layers

Semiconductors - Various methods for the formation of ohmic contacts to boron-doped δ layers in CVD-diamond epitaxial structures are investigated. In the first variant, an additional thin...     

Structural Features of Textured Zinc-Oxide Films Obtained by the Ion-Beam Sputtering Method

Semiconductors - Textured ZnO films obtained on amorphous substrates using the ion-beam sputtering method are studied. X-ray diffraction and atomic-force microscopy methods show that the resulting...     

Triterpene glycosides from Astragalus and their genins. LXXVIII. Chemical transformation of cycloartanes. VI. Partial synthesis of cycloadsurgenina

Cycloadsurgenin, 20R,24 S-epoxycycloartan-6α,25-diol-3,16-dione, was partially synthesized in four steps from cyclosieversigenin. Side products with the structures 17E,24S-cycloart-17-en-6α,24,25-triol-3,16-dione and 17Z,24 S-cycloart-17-en-6α,24,25-triol-3,16-dione were obtained in addition to the desired product. Presented at the 1st International Symposim on Edible Plant Resources and the Bioactive Ingredients, Xinjiang, China, July 25–27, 2008. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 591–595, November–December, 2008.     

O–H···C hydrogen bond in the methane–water complex

Quantum chemical calculations were performed at different levels of theory (SCF, DFT, MP2, and CCSD(T)) to determine the geometry and electronic structure of the HOH···CH₄ complex formed by water and methane molecules, in which water is a proton donor and methane carbon (sp³) is an acceptor. The charge distribution on the atoms of the complex was analyzed by the CHelpG method and Hirshfeld population analysis; both methods revealed the transfer of electron charge from methane to water. According to the natural bond orbital (NBO) analysis data, the charge transfer upon complexation is caused by the interaction between the σ orbital of the axial С–H bond of methane directed along the line of the O–H···C hydrogen bridge and the antibonding σ* orbital of the О–H bond of the water molecule. Topological analysis of electron density in the HOH···CH₄ complex by the AIM method showed that the parameters of the critical point of the bond between hydrogen and acceptor (carbon atom) for the O–H···C interaction are typical for Н-bonded systems (the magnitude of electron density at the critical point of the bond, the sign and value of the Laplacian). It was concluded that the intermolecular interaction in the complex can be defined as an Н bond of O–H···σ(С–H) type, whose energy was found to be 0.9 kcal/mol in MP2/aug-cc-pVQZ calculations including the basis set superposition error (BSSE).     

Modifying the surface of a hydrogen permselective palladium–silver membrane

Thin films of Pd–23% Ag composition are obtained by means of magnetron sputter deposition. The surfaces of the films are modified via the electrolythic deposition of finely divided palladium. The hydrogen permeabilities of samples of membranes (both smooth and modified with palladium black) are compared. A marked increase in the hydrogen permeability of the modified membrane is observed, compared to the smooth membrane. The dependence of the rate of hydrogen fluence on the excess pressure is approximated by a curve of the first order, demonstrating the limitations of the process of hydrogen permeation by hydrogen superficial dissociation.     

Effect of structural relaxation on the binding energy in a molecular complex. The role of relaxation in the formation of intermediate for nucleophilic reactions of carbonyl compounds

The problem of a change in the geometry of interacting molecules, based on harmonic approximation, is considered here, to describe the effect of structural relaxation in the formation of a molecular complex on the binding energy. The correlation between the relaxation and deformation energies found earlier was analyzed with the use of an harmonic model of a molecular complex. To verify the correlation, calculations on the molecular complexes of different kinds were carried out using ab initio and semiempirical AM1 quantum chemical methods. The effect of structural relaxation on the properties of the potential energy surface for reactions of nucleophilic addition to carbonyl compounds is discussed.     

Collective Acceleration of Ions in a Pulsed Magnetic Field of a Conical Spiral

The collective acceleration of laser plasma ions in a magnetic field generated by a powerful fast-growing current pulse in a low-inductive conical spiral is studied. The velocity of ions for a number of elements which significantly differ in atomic weight are obtained on the basis of collector measurements. The maximum velocity of both light (lithium) and heavy (lead) ions exceed the value of 108 cm/s; for ions of lead, the corresponding energy amounts to a value of ∼1 MeV. A mathematical model of ion acceleration is proposed and simulation results are compared with the experiment.