Multistep electrochemical reactions involving transport of intermediates between the near-electrode layer and the bulk solution: A kinetics analysis based on theory of generalized variables (theory of similarity)

A kinetic analysis of multistep electrochemical reactions involving partial diffusion transport of intermediates between the near-electrode layer and the bulk electrolyte is performed within theory of generalized variables (theory of similarity). Dimensionless complexes (similarity criteria) that characterize such reactions are obtained, and their values corresponding to the transport of intermediates are determined.Translated from Elektrokhimiya, Vol. 41, No. 1, 2005, pp. 121–125.Original Russian Text Copyright © 2005 by Protsenko, Danilov.     

Defect structures and three-body potential of the mean force for nanoparticles in a nematic host

We have investigated the defect structures and potential of mean force (PMF) of three colloidal spheres immersed in a nematic liquid crystal (for linear and equilateral-triangular configurations), using a coarse-grained theory for the tensor order parameter. At large separations, each sphere is surrounded by an equatorial Saturn ring defect; at short separations, the theory predicts a drastic reorganization of the disclination lines: additional disclination rings are observed in planes perpendicular to the original ones. For both types of configurations, the PMF is attractive and always greater than a pairwise sum of binary PMFs. Comparing the PMFs of linear and equilateral-triangular configurations, we have found the triangular configuration to be more stable than the linear configuration. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1033-1040, 2005     

Variational treatment on the energy of the He‐sequence ground state with weakest bound electron potential model theory

The concept of spin–orbital of the weakest bound electron is described used to construct the antisymmetric wave function of atomic or ionic systems within weakest bound electron potential model theory (WBEPM theory). The total energies of He‐sequence (Z = 2–9) in the ground states is calculated with a variational method. The effect of fixed orbital approximation is discussed quantitatively. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Study and Thermodynamic Analysis of the ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> System

The system ZrO₂-SiO₂ was additionally studied by means of differential thermal analysis. The temperatures of the solid-state decomposition of zircon and the coordinates of the eutectic point were refined. A thermodynamic calculation of the system in terms of the theory of subregular ionic solutions was carried out on the basis of the experimental data obtained.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 207–210.Original Russian Text Copyright © 2005 by Kamaev, Archugov, Mikhailov.     

A new attempt to reconcile the statistical and phenomenological theories of rubber elasticity

The statistical and phenomenological theories of rubber elasticity are reviewed briefly. Combining recent concepts proposed by Yeoh and Gent, a new theory is proposed. The proposed constitutive model for rubber vulcanizates invokes two mechanisms; one influences behavior at small strains while the other dominates behavior at large strains. Network flaws, such as entanglements, are suspected to be responsible for the first mechanism. Finite extensibility of network chains is identified as the cause of the second. Thus, macroscopic behavior is directly linked to molecular concepts. The proposed theory allows prediction of the stress–strain behavior of a family of four rubber vulcanizates in different modes of deformation (simple extension, compression, and simple shear) from regression analysis of tensile data alone from just one member. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1919–1931, 1997     

Multicenter bonding within the AIM theory

This study reports the incorporation of recently proposed formalism for the detection and localization of multicenter bonding in molecules, the so-called generalized population analysis, into the framework of the atoms in molecules (AIM) theory. The reliability of this new approach is tested by direct numerical comparison of the values of multicenter bond indices derived from both the original and the AIM-generalized forms of the population analysis. Received: 1 June 2000 / Accepted: 11 October 2000 / Published online: 23 January 2001     

Equation of state for high density solid and melt polyethylene

Pressure‐volume‐temperature (PVT) measurements for high‐density linear polyethylene (LPE) are studied experimentally over a temperature range of 290 to 470 K and pressures up to 3.1 kbar. For melt, the results can be represented by the Tait equation within the precision of the data. It is noticed that for each isotherm, an abrupt departure from the Tait representation occurs at a particular pressure. This is ascribed to onset of solidification due to pressure. Further, variation of the degree of crystallinity with pressure at various temperatures has been investigated. Finally, the PVT data has been analyzed in terms of the LJD cell theory in its original form without any modifications or simplifications of the cell potential. Satisfactory agreement is obtained between experiment and theory over the entire range of PVT data both in solids and melt states. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1618–1623, 2005     

A DFT Study of Acetylenic Alkali Metal Thiolates

Quantum-chemical calculations by the density functional theory (DFT) method showed that of acetylenic thiolates and their structural analogs, thioketene or thiirene anions, acetylenic thiolates and thioketene anions are only stable, and the negative charge in them is mostly localized on the sulfur atom.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1206–1210.Original Russian Text Copyright © 2005 by Petrov, Belyakov.     

Density functional studies on hydrogen‐bonded clusters of hydrogen halides and the interaction on halide anions

Density functional theory (DFT) calculations have been performed to study the structures and stability of X^?·(HX)_n=2–5 clusters where X = F, Cl, Br at B3LYP/6‐311++G** level of theory. The presence of halide ions in these clusters disintegrates the hydrogen halide clusters. All the hydrogen halides are then hydrogen bonded to the centrally placed halide ions, thereby forming multiple hydrogen bonds. The interaction energies have been corrected for the basis set superposition error (BSSE) using Boy's counterpoise correction method. Evidence for the destruction of hydrogen bonds in hydrogen halide clusters due to the presence of halide ions is further obtained from topological analysis and natural bond orbital analysis. The chemical hardness and chemical potential have been calculated for all the anion clusters. The above analysis reveals that hydrogen bonding in these systems is not an essentially electrostatic interaction. The nature of the stabilization interactions operative in these multiple hydrogen‐bonded clusters has been explained in terms of many‐body contribution to interaction energies. From these studies, an attempt has been made to understand the nature of the molecular properties resulting from different electronegativities of the halogens. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

New polydentate macrocyclic ligands of hybrid amine-imine and amide-imine types as artificial anion receptors. Synthesis and study of anion binding

Three new macrocyclic Schiff bases containing an amine or amide structural fragment along with imine groups were synthesized by condensation of 2,6-bis(2-aminophenyliminomethyl)pyridine (1) and N, N’-bis(2-aminophenyl)pyridine-2,6-dicarboxamide (2) with 2,5-diformylpyrrole (₃) and 2,2-bis(5-formylpyrrol-2-yl)propane (4). The reaction of compound 1 with 3 proceeds abnormally and is accompanied by redox disproportionation of compound 1 in the first step. The structure of the macrocyclic product of this reaction was established by X-ray diffraction analysis. Spectrophotometric titration showed that hybrid macrocycle 10, which was prepared by condensation of compound 2 with 4, possesses the properties of an anion receptor and selectively binds hydrosulfate and dihydrophosphate anions in the presence of bromide and nitrate anions. The structures of 10 and its adduct with the hydrosulfate anion were calculated by density functional theory.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 161–168, January, 2005.     

Critical properties of thin films of polymer solutions

The critical properties of polymer solutions confined in thin‐film environments is studied with simple scaling arguments and a molecular theory. For purely repulsive surfaces, the critical volume fraction is a universal function of x = N^1/2/L, where N is the chain length and L is the film thickness. The critical volume fraction is nonmonotonic in x and shows a deep minimum at a film thickness several times larger than the chain's radius of gyration. This nonmonotonic behavior results from the interplay between the surface–polymer entropic repulsion and the tendency of the film to avoid large density gradients. The critical temperature is a monotonically increasing function of L, as L goes from the two‐dimensional limit to the three‐dimensional limit. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1849–1853, 2005     

Calculation of the Magnetic Properties of Low-Symmetry Polynuclear Complexes. Exchange Interactions in the Hexanuclear Chromium(III) Pivalate

A theory that allows numerical calculations and interpretation of magnetic properties of low-symmetry polynuclear complexes containing a large number of orbitally non-degenerate transition metal ions is developed by the irreducible tensor operator method. The potential of the theory was illustrated using the chromium(III) complex, Cr₆O₂(OH)₂[O₂CC(CH₃)₃]₁₁ as an example.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 518–522.Original Russian Text Copyright © 2005 by Rakitin, Smith.     

Calculation of the Magnetic Properties of <Emphasis Type="Italic">d</Emphasis> and <Emphasis Type="Italic">f</Emphasis> Transition Metal Complexes in Terms of the Angular Overlap Model

The theory of the electronic structures and magnetic properties of mononuclear complexes of d and f transition metals was developed in a complete basis set of products of one-electron functions with the use of the parametrization adopted in the angular overlap model. It was demonstrated that the theory describes well the temperature dependences of the magnetic susceptibilities of these complexes and allows estimation of their detailed electronic structures.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 506–511.Original Russian Text Copyright © 2005 by Rakitin, Rakitina, Kalinnikov.     

Determination of the Working Exchange Capacity of Weakly Basic Polyacrylic Anionites

The nonequilibrium dynamics of sorption of hydrochloric acid by weakly basic polyacrylic anionites was studied. An equation for calculating the working capacity of ion-exchange filters as a function of variable parameters (filtration rate, concentration of the starting solution, and height of the ionite bed in a filter) was derived using the theory of nonequilibrium dynamics of sorption.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 6, 2005, pp. 905–911.Original Russian Text Copyright © 2005 by Mamchenko, Savchenko.     

Chemical bond inside a fullerene cage: is it possible?

The geometries, electronic structures, and hyperfine coupling constants of azafullerene C₅₉N (a π-electron radical) and its derivatives, C₅₉NH and endofullerene H@C₅₉N, were calculated at the B3LYP level of the density functional theory. Analysis of calculated potential energy profiles along trajectories of the motion of encapsulated hydrogen atom from the center of the fullerene sphere toward different atoms of C₅₉N revealed formation of a chemical bond between the H atom and a carbon atom that is involved in the 6,6-bond with the N atom and bears the most part of the π-electron spin density. The C—H endo-bond length is 1.12 Å, the bond dissociation energy being equal to 26.4 kcal mol⁻¹. The C—H exo-bond involving the same carbon atom is 0.02 Å shorter than the endo-bond, the bond dissociation energy being much higher (78.4 kcal mol⁻¹).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 51–54, January, 2005.     

Electrokinetic Potential of Particles in Suspensions and Donnan Equilibrium in a Thin Gel Film

The influence exerted by the thickness of a gel layer on the difference of the electric potentials of phases and on the distribution of the potential near the phase boundary are considered in terms of the classical theory of the Donnan equilibrium in a two-phase system constituted by a gel and an electrolyte solution. The results obtained make it possible to explain a number of experimental facts.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 224–228.Original Russian Text Copyright © 2005 by Bibik.     

Modeling Gas Chromatography with a Specified Temperature Dependence of Henry’s Law Constant

A derivation of the chromatographic curve equation and kinetic mechanisms that determine the diffusion broadening of chromatographic peaks are considered in detail. Being combined with the theory of adsorption in the Henry region, this work has served as a basis for the development of the MOLCHROM program for modeling the gas chromatography process. An example demonstrating the adequacy of the program and its usefulness in selecting separation conditions for complex mixtures is given.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 7, 2005, pp. 723–728.Original Russian Text Copyright © 2005 by Prudkovskii.     

A simple optimization strategy based on Rs-minimum and information theory of chromatography

Summary A simple optimization method based on the well-known Rs-minimum method and on the information theory of FUMI Φ is proposed. Resolution (Rs), peak area and height (or width) are the only parameters necessary for the calculation of the information Φ and information flow ϑ. The most precise analysis can be selected as the chromatogram having maximal ϑ. Mobile phase composition, column length, flow rate, detection wavelength, amount of internal standard, etc. can be optimized by this method.     

Scale Factor upon the Grain Boundary Wetting in Polycrystals

The intergrain penetration of wetting liquids (water and gallium) is studied with polycrystalline samples of NaCl and zinc, respectively. A strong effect of a scale factor is found. The quantitative correlation between the results of simulation and the data of physical experiments is established and is indicative of the applicability of the percolation theory to describe the process of intergrain wetting.__________Translated from Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 404–409.Original Russian Text Copyright © 2005 by Traskine, Volovitch, Protsenko, Kucherinenko, Skvortsova.