Long-wavelength dynamics of the two-dimensional antiferromagnet

We perform the long-wavelength reduction of the two-dimensional quantum lattice rotator model. An intermediate scale is introduced and the short-wavelength antiferromagnetic spin fluctuations are integrated out. The saddle-point solution for the generalized continuous sigma-model in terms of parameters of the initial model is constructed.     

Local structure of Gd3+ impurity center at cubic sites in fluorites

A computer controlled ENDOR spectrometer and special software are used to determine the coordinates of¹⁹F nuclei in four anionic spheres of cubic MeF₂:Gd³⁺ (Me = Ca, Sr, Ba, Pb) centers. The computer simulation of Gd³⁺ cubic impurity center in crystals MeF₂ (Me = Ca, Sr, Ba) has been also performed. The analysis of lattice relaxation near the impurity center carried out on the base of ENDOR experiments data has allowed us to obtain potential of interaction Gd³⁺-F^?. For the first time not only radial displacements but also angular displacements of F^? ions of the third sphere have been taken into account and it has been shown that it influences the determination of lattice relaxation around the impurity center essentially. The influence of hydrostatic pressure (up to 30 kbar) on the local structure of the impurity center has also been investigated using computer simulation. The comparison of the experimental and calculated displacements of distant ions gives a reliable test of the validity of theoretical lattice relaxation model and accuracy of calculations of impurity-directed shifts of ligands.     

Topological analysis of Ge-O bonds in trichlorogermanes Cl3GeCH2YC(O)R

The density functional theory (DFT) method (GAUSSIAN-98 software, B3LYP functional, 6-311G(d,p) basis set) was used to calculate the spatial and electronic structures of a series of trichlorogermanes with the general formula Cl₃GeCH₂YC(O). AIM calculations gave the topological characteristics of the Ge-O dative bonds of these molecules. Analysis of the results showed that Ge and O atoms interact as closed-shell atoms and that the major contribution to Ge-O bonding is from Coulomb interaction between the germanium and oxygen atoms charged in the opposite sense.     

Reaction paths of the formation and consumption of nitroorganic complex intermediates in the selective catalytic reduction of nitrogen oxides with propylene on zirconium dioxide according to in situ Fourier transform IR spectroscopic data

Nitrate, acetate, and nitroorganic complexes were detected on the surface of ZrO₂ under the reaction conditions of nitrogen oxide reduction with propylene using Fourier transform IR spectroscopy. The nitroorganic complex was formed in the reaction between acetate and nitrate complexes by the replacement of the carboxyl group in the acetate complex by the nitro group. Monodentate nitrate was the most reactive species in this process. The adsorption of various nitroorganic substances was studied. It was found that the nitroorganic complex was structurally analogous to the nitromethane molecule bound to the surface through the nitro group. The experimental data led us to a conclusion that nitroorganic compounds were subsequently consumed in reactions with nitrate complexes. In this surface reaction, monodentate nitrate was also the most reactive species. The presence of oxygen had no effect on the consumption of the nitroorganic complex.     

Structures of the covalent hydrates and products of acidic hydrolysis of rheumycin and fervenulin

It is shown that pyrimido[5,4-e]-1,2,4-triazinediones are hydrated at the N(₄)-C(_4a) bond in aqueous acidic media. The equilibrium constants of these processes were measured by PMR spectroscopy. The structure of the covalent adduct of fervenulin was established by x-ray diffraction analysis. Formic, 5-diazo-3-methylbarbituric, and methylparabanic acids were identified among the products of destruction of the hydrates in acidic media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1654–1660, December, 1988.     

O,N-Dimethylation of 5,6-dihydroxynicotinic acid

AnO,N-dialkylation product, 1-methyl-5-metlioxy-6-oxo-1,6-diliydropyridine-3 carboxylic acid, is formed in the reaction of 5,6-dihydroxynicotinic acid with dimethylsulfate.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1554–1555, June, 1996.