Relaxation Effect of Basis Orbitals on the Properties of Atomic and Molecular Hydrogen Systems

The effect of orbital relaxation on the properties of atomic and molecular hydrogen systems H, H ₂ ⁺ , H₂, H ₂ ⁻ , and H ₃ ⁺ calculated using the minimal basis set, the split valence shell basis set including the polarization function, and an extended basis set of grouped natural orbitals is considered. Inclusion of orbital relaxation in calculations results in a decreased total energy and more accurate energies of electron affinity. The strongest effect is produced on the calculated characteristics of the anions. The calculated activation energy of the radical reaction of hydrogen elimination. H₂ + H = H + H₂ depends strongly on the degree to which electron correlation is taken into account. Due to inclusion of orbital relaxation, the activation energy also approximates the experimental value, although to a lesser extent. The semiempirical PM3 method fails to adequately describe the transition state of this reaction, but this disadvantage is eliminated by using the exponent of the relaxed orbital of hydrogen.Original Russian Text Copyright © 2004 by A. I. Ermakov, A. E. Merkulov, A. A. Svechnikova, and V. V. Belousov__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 979–985, November–December, 2004.     

C-Phosphorylation of Formamidines

C-Phosphorylation of formamidines by trivalent phosphorus halides was researched. Direction of the phosphorylation depends on nature of substituents at the amidine nitrogens. C-Phosphorylated products was shown to be of valuable possibilities to construct phosphoruscontaining heterocycles     

Sharpening of carbon nanocone tips during plasma-enhanced chemical vapor growth

In situ tip sharpening of vertically aligned carbon nanocones (VACNCs) was demonstrated. VACNCs were synthesized on patterned catalyst dots of 100 nm in diameter using dc plasma-enhanced chemical vapor deposition. The VACNC tip diameter was found to decrease with growth time. This enables synthesis of ultra-sharp VACNCs even for relatively large catalyst dot sizes, which is quite important for practical applications. We also find that for a given set of growth parameters the diameter of the initially formed catalyst nanoparticle determines the maximum length of the growing VACNC. The mechanism of VACNC growth and sharpening is discussed.     

Configuration of cones of singular optic axes in magnetically ordered crystals with orthorhombic syngony

We demonstrate the possibility of the existence of 12 topologically different types of cones of singular optic axes in magnetically ordered crystals having orthorhombic syngony, depending on the parameters of the non-Hermitian inverse dielectric tensor.     

Organometallic synthesis and electrophoretic characterization of high-quality ZnS:Mn/ZnS core/shell nanoparticles for bioanalytical applications

A novel and facile preparation method for colloidal ZnS nanoparticles doped with Mn²⁺ is introduced, using a simple one pot heating process followed by a capping procedure for saturation of the surface bound doping atoms to increase the nanoparticles’ stability and photoluminescence quantum yield. The particles were transferred into water with a standard ligand exchange method and investigated by means of laser Doppler electrophoresis, agarose gel electrophoresis, and isotachophoresis. Correspondence: Alexey Merkulov, Freiburg Materials Research Centre (FMF), University of Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg, Germany     

Crystal Structure of KTP and KTA. I. Structure of the Potassium–Oxygen Nets and Differences between K+ Sites 1 and 2

The potassium–oxygen nets in the {420} planes of potassium titanyl phosphate (KTP) and its structural analogs are considered. The factors governing the stability of the structure are revealed. It is shown that the net analysis permits one to establish the fine structure of the Z-pores and the distinctions of the K(1) and K(2) structural sites. Models of domain walls in KTP and analogous crystals are suggested.     

InF<Subscript>3</Subscript>-based bismuth-containing glasses

Glasses have been prepared in the InF₃-BiF₃-BaF₂-PbF₂-ZnF₂-LnF₃ (Ln = Eu, Tm) system. The short-range and medium-range order structure of the glass network is discussed on the basis of IR and Raman spectroscopy data. The effect of bismuth trifluoride on the thermal properties, structure, and photo-luminescence properties of glasses was studied. Bismuth trifluoride doping improves the thermal parameters of glasses. The polyhedra formed by bismuth trifluoride in the glass are not involved in the medium-range order. In rare-earth-containing glasses, strong photoluminescence was discovered in the range 530–560 nm with excitation by the Raman-masking 532-nm wavelength. Bismuth in the glass enhances the europium photoluminescence level in the glass of the InF₃-BiF₃-BaF₂-PbF₂-ZnF₂-EuF₃ system.     

Homo- and heteroleptic cobalt(II) and nickel(II) complexes with nitrilotriacetic and dibasic carboxylic acids

Equilibria in binary and ternary systems containing cobalt(II) and nickel(II) salts, nitrilotriacetic acid, and dicarboxylates were studied by spectrophotometry with NaClO 4 as a supporting electrolyte (I = 0.1) at T = 20 ± 2°C. The molar and proton compositions of the complexes and the pH ranges of their existence were determined. The stability constants of the homo- and heteroleptic complexes were calculated. The pH-distribution of the detected complexes was obtained. The experimental data were processed in terms of the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow ignoring those species that are negligible for accurate reproduction of the observed pattern.     

Crystal structures of MnNbOF5 · 4H2O at 153 and 297 K

Crystals of MnNbOF₅ · 4H₂O were studied by X-ray diffraction, differential scanning calorimetry (DSC) and thermogravimetry. DSC showed a phase transition in the temperature range of 282 to 296.3 K. The compound is dehydrated in two stages in the temperature ranges of 65–131.1 and 131.1–190°C, two H₂O molecules being removed in each stage. The structure of MnNbOF₅ · 4H₂O was determined at 153 K (α phase; space group P2₁/c) and at 297 K (β phase, space group C2/m). The structure of both phases is formed of the octahedral complexes [NbF₄(O/F)_2/2]^0.5? and [Mn(H₂O)₄(O/F)_2/2]^0.5+ linked by bridging O and F atoms to infinite chains. The isolated niobium-manganese chains are connected by O-H…F hydrogen bonds. In the α phase, the Nb, O, and F atoms in the trans position relative to O are disordered with respect to the inversion center of the structure. Transition to the β phase is accompanied by splitting of all ligand positions at the Nb and Mn atoms into two equally probable positions.