Исследование магнитных свойств ферроборатов неодима и самария методом спектроскопического эрбиевого зонда

Iron borates NdFe3(BO3)4 and SmFe3(BO3)4 activated with 1% erbium, with a huntite structure (space symmetry group R32) were investigated by the method of erbium spectroscopic probe. From an analysis of the temperature dependence of the transmission spectra in the region of the 4I15/2→4I13/2 transition in the Er3+ ion, it was found that both studied compounds order antiferromagnetically at TN ≈ 33 K into an easy-plane magnetic structure. No other phase transitions were found.

MATHEMATICAL MODELING OF THE CRYSTAL STRUCTURE OF PEROVSKITE-LIKE MATERIALS

The paper presents the calculation of the metric parameters of crystalline compounds according to a given chemical formula and a space symmetry group. The structures of perovskite and double perovskite are considered.

SYNTHESIS AND STRUCTURE OF TRIPHENYLBUT-2-ENYL- AND TRIPHENYLMETOXYMETHYLPHOSPHONIUM HEXACHLOROZIRCONATES

Triphenylbut-2-enyl- (1a) and triphenylmetoxymethylphosphonium (1b) hexachlorozirconates have been synthesized by the reactions of zirconium tetrachloride with the triphenylalkylphosphonium chlorides in acetonitrile for the first time and characterized by the IR, NMR spectroscopy and X-ray analysis. The most intensive bands in IR spectra correspond to the valence vibrations of the CAr-H and the СAr-СAr bonds in the triphenylalkylphosphonium cations. The splitting of carbon atoms signals is observed due to the presence of 13C – 31P coupling. SSCC for carbon atoms directly connected with phosphorus are about 48–85 Hz. According to the X-Ray data, compound 1a crystallizes in the monoclinic crystal lattice (the P21/c space symmetry group). Hexachlorozirconate 1b forms the triclinic crystals belong to the P-1 space symmetry group. Crystals of compound 1a is characterized by the less dense molecular packing in the crystal lattice in comparison with compound 1b. Calculated densities for the structures 1a,b are 1.355 g/cm3 and 1.466 g/сm3, respectively. Structural organization of the complexes in crystals is caused by the formation of hydrogen bonds between chlorine atoms of the anion and hydrogens of phenyl and alkyl groups of the cations. The phosphorus atoms in the triphenylalkylphosphonium cations have distorted tetrahedral coordination (CPC 107.01(4)°-114.10(6)° for 1а, 107.38(9)°-112.06(7)° for 1b, the P-С bonds are 1.790(14)-1.865(14) Å for 1а, 1.7838(12)-1.8293(18) Å for 1b). In centrosymmetric octahedral anions [ZrCl6]2− (trans-ClZrCl 180°) the Zr-Cl distances are 2.4654(15)-2.4952(17) Å for 1а and 2.4641(14)-2.4711(12) Å for 1b.

PREPARATION, DIELECTRIC AND OPTICAL PROPERTIES OF Cr2O3 /PVC NANOCOMPOSITE FILMS

Chromium oxide (Cr2O3) nanoparticles were synthesized using a sol-gel method and mixed with polyvinyl chloride (PVC). Rietveld refinement of X-ray powder diffraction (XRD) patterns of the samples revealed that the crystal structure of Cr2O3 is rhombohedral with space symmetry group. Scanning electron microscopy images showed that the Cr2O3 nanoparticles are well dispersed on the surface of the PVC films. The dielectric permittivity (e'), and ac conductivity (σac) of pure PVC increased with adding Cr2O3 due to the formation of conductive three-dimensional networks throughout the nanocomposite films and interfacial polarizations. The optical energy band gap (Eg) of the films decreases with increasing Cr2O3 content. The refractive index dispersion of the nanocomposite films obeys the single oscillator model. The dispersion parameters are changed by incorporation of Cr2O3. The optical properties of PVC are influenced by addition of Cr2O3 nanoparticles.

A Reactive System with Diffusive Transport Displaying Two Different Symmetry-Breaking Dissipative Structures

An open reactive system is modelled by coupling the chemical kinetics to diffuse transport. This system operates far from the regime of linear irreversible thermodynamics. The kinetics correspond to a certain region in the parameter space of the Oregonator for which two symmetrybreakdowns occur: a) A periodic orbit contained in an unstable manifold of the phase space. This solution is invariant under time-translations generated by a period. b) A spatial stationary dissipative structure. This solution is invariant under a subgroup of the space symmetry group. The initial time periodicity of the system is followed by a spatial pattern. The restriction to the center manifold in the phase space allows to reduce an infinitedimensional problem for the bifurcation of a semiflow to a finite dimensional system of ordinary differential equations. The ranges in the control concentrations for this dynamics is found in accord with the experimental values. We also demonstrate that if the vessel is stirred after the Turing pattern has emerged, the freezed wave is destroyed and the time-periodic behavior is achieved again.

Crystal and molecular structure of dinickel(II) (S,S)-ethylenediamine-N,N'-disuccinate heptahydrate

[Ni2(S,S)-EDDS].7 H2O structure has been solved by the heavy atom method and by the least squares method at R = 0.058; the substance crystallizes in orthorhombic system and space symmetry group P212121 with the lattice parameters a = 0.9904 (5), b = 1.2477 (8), c = 1.6036 (17) nm. The crystal structure is composed of the binuclear units Ni2(H2O)5[(S,S)-EDDS] and molecules of crystal water. The anion [(S,S)-EDDS]4- coordinates to Ni(II) as a stereospecific hexadentate ligand, the six-membered β-alanine rings being situated in equatorial plane of the coordination polyhedron, the glycine rings being axial. Absolute configuration of the complex anion is (OC-6-13-A).