Vol 63, No 7 (2018)

Results of longitudinal X-ray diffraction studies of the structural organization of biological tissues from humans and animals in different physiological states using Russian sources of synchrotron radiation from the VEPP-3 and Siberia-2 storage rings are presented. The X-ray diffraction patterns of mucus and epithelial tissues show many orders of Debye rings at the main spacing of 4.65 (±0.15) nm, which was attributed to proteoglycan systems of the extracellular matrix of different tissues. The periodicity was experimentally shown to be invariable at a nanoscale level in a broad evolutionary framework. The nanostructural transformation of proteoglycan systems was found to be induced by the synergistic effect of high-frequency electrosurgical welding, which is widely used in clinical surgery. Through the lens of statistical physics of polymer networks, proteoglycans can be considered as labile systems capable of modifying adaptation through the formation of reversible chelate complexes with calcium cations.

Minimal generating sets for 17 2D-space (plane) groups have been derived. The concept of fuzzy generating set of a group is introduced. The considered groups are compared with respect to the degree of fuzziness of their generating sets.

A crystallochemical analysis of synthetic layered lithium-containing silicates has been performed. It is shown that these compounds have unique properties and structural characteristics. According to the X-ray diffraction data, the initial material possess a layered structure. After filling the material with ethylene glycol, the intensity of the reflection corresponding to the interplanar spacing d₀₀₁ = 12.3 Å significantly decreased, and two additional peaks arose: strong (d = 16.8 Å) and weak (d = 14.7 Å), which indicates possible presence of three layered phases with different sorption properties in the sample. The samples easily absorb moisture from air. The range of stretching vibrations of OH groups in the IR spectra of synthesized samples corresponds to the spectrum of adsorbed water.

The structural model and chemical composition of vlasovite from the Burpala massif (Russia) have been determined using X-ray diffraction methods and electron probe microanalysis. The crystal structure has been refined in the sp. gr. Cc to R = 1.4% (R_w = 1.8%) with the following unit-cell parameters: a = 11.0396(3) Å, b = 10.1042(2) Å, c = 8.5696(2) Å, β = 100.307(1)°, V = 940.48(4) ų, and Z = 4.

The crystal structures of Bi_1 – xPr_xFeO₃ solid solutions in the vicinity of the transition from the polar rhombohedral phase to the nonpolar orthorhombic phase have been analyzed by X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. These methods made it possible to reveal the specific features of the change in the crystal structures of the solid solutions with an increase in temperature in dependence of their structural state at room temperature. The analysis of the structural data indicates the presence of antipolar orthorhombic phase in the compounds with dominant rhombohedral phase at the temperature transition to the nonpolar state. The evolution of the crystal structures of Bi_1 – xPr_xFeO₃ solid solutions with a change in the concentration of praseodymium ions and temperature has been considered, and the role of the antipolar orthorhombic phase as an intermediate phase in the structural transition from the rhombohedral phase to the nonpolar orthorhombic phase has been discussed.

A technique for growing 2,3-7,8-dibenzpyrene-1,6-quinone single crystals is described. Its crystal structure, IR transmission spectra, reflection spectra in the visible spectral range, results of thermal analysis, and XPS spectroscopy data are reported for the first time. The crystalline structure of this compound is described within the sp. gr. P2₁/n; its unit cell parameters are a = 17.4346(19) Å, b = 4.8717(5) Å, c = 18.263(2) Å, and β = 105.857(2)°. The structure can be characterized as a herringbone stacking of flat molecules, between which weak О…H‒C interactions of carbonyl oxygen atoms and hydrogen atoms of aromatic rings exist.

A nickel coordination polymer with V-shaped ligands, {[(L¹)₂Ni(H₂O)₂] · 2(C₈H₅O₄)}_n, (L¹ = 4-(1H-imidazol-1-yl)phenyl)methanone) has been synthesized under the solvothermal conditions. The structure has been determined by the single-crystal X-ray diffraction analysis and characterized by the infrared spectroscopy and elemental analysis. The crystal is crystallized in the monoclinic sp. gr. P2₁/c with the unit cell parameters a = 15.6387(3) Å, b = 8.0526(2) Å, c = 24.4791(6) Å, and β = 129.2350(10)°, Z = 2. The adjacent [Ni(H₂O)₂] units are linked by two bridging L¹ ligands to form 1D looped chains, which are extended by the hydrogen bonds to yield a 3D framework.

A novel cobalt complex, (L¹)₂Co₂(hfac)₄, (1), where L¹ is (2E, 5E)-2, 5-bis(pyridin-3-ylmethylene)cyclopentan-1-one, has been synthesized and characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The crystal of 1 is monoclinic, sp. gr. P2₁/c with the unit cell parameters a = 8.9700(3), b = 10.9323(4), c = 31.5197(11) Å, and β = 102.470(3)°, Z = 2, R₁ = 0.0866, and wR₂ = 0.2528 (I > 2σ). The Co²⁺ ion has a distorted tetrahedral environment with four O atoms from two hfac ligands and two N atoms from two L¹ ligands. The solid state of 1 consists of numerous hydrogen bonds, which are propagating the molecules to form a 3D network.

The pentadentate N₄O-type Schiff base ligand was obtained by the condensation reaction of salicylaldehyde and tris(2-aminoethyl)amine, and its novel Zn(II) complex [Zn₂ (C₁₃H₂₁N₄O)]Cl₃ was synthesized. The compounds were characterized by IR, UV–Vis, ¹H-, ¹³C-NMR spectroscopy. Crystal structure of the complex was determined by X-ray single crystal diffraction. Complex crystallizes in the monoclinic system with sp. gr. P2₁/c and shows the ligand coordinated to two Zn ions with different structures around metal ions. One Zn(II) ion is five-coordinated: its coordination polyhedron is intermediate between trigonal bipyramid and square pyramid, being 30.1% along the pathway from trigonal bipyramid to square pyramid. Another Zn(II) ion has a tetrahedral structure. The electronic spectrum of the complex showed ligand to metal charge-transfer bands.

K_1 – хCs_хNO₃ (х = 0.015, 0.035) single crystals have been synthesized from aqueous solutions. Polymorphic transformations in them at temperatures from room to melting have been investigated by X-ray diffraction. The existence of two polymorphic crystal modifications in this temperature range is established. Transformation temperatures and unit-cell parameters of the modifications are determined.

A method for determining the temperature dependences of the lattice parameters of ferroelectrics in the presence of two successive structural m3m–4mm–mm2 phase transitions, provided that the paraelectric-phase macrosymmetry is preserved in a polydomain crystal, has been proposed. Three analytical solutions for the second-order phase transition are obtained on the example of KNbO₃. Two solutions are shown to correspond to changes in the lattice parameters of the tetragonal and orthorhombic phases. It is revealed that the value of the spontaneous polarization in KNbO₃ depends on the temperatures of two phase transitions: first-order phase transition and preceding hypothetical second-order phase transition.

CdGa₂S₄ single crystals (a = 5.555 ± 0.002 Å, c = 10.190 ± 0.005 Å) have been grown by the chemical transport reaction (CTR) method, and their dielectric properties have been analyzed. An experimental study of the frequency dependence of the dielectric coefficients and conductivity of the CdGa₂S₄ single crystal has made it possible to reveal the nature of dielectric losses, establish the hopping charge-transfer mechanism, and estimate the parameters of localized states (density and energy spread of states near the Fermi level; mean duration and length of hops; and concentration of deep traps, which implement ac conductivity).

The temperature dependences of the optical path difference ∆_і(Т) and relative changes δl_і/l_і in the thickness of Rb₂ZnCl₄ crystals have been studied. The temperature dependences of the relative changes in the refractive indices δn_і/(n_і – 1) are calculated. The critical index of the temperature changes in the refractive indices is estimated to be β = 0.31 ± 0.02, a value that is well consistent with the Landau theory of phase transitions. The coefficients of anisotropy of refractive indices А_n – 1(Т) are calculated. A characteristic minimum near the phase transition temperature is found in these dependences.

The physical properties of solid structures depending on the boundary conditions in topologically ordered nanocluster systems are discussed. These systems are synthesized using various laser methods in the form of metal/semiconductor nanostructures/nanoclusters and thin films on solid substrates. A particular attention is paid to the possible mechanisms and tendency to high-temperature superconductivity in these thin-film nanocluster structures.

The effect of the Al–Ga melt composition on the mass transfer processes occurring during silicon recrystallization has been investigated by the thermomigration method. The threshold temperatures of thermomigration onset are determined. The kinetic regularities of liquid zone thermomigration, related to the recrystallization temperature and liquid phase composition, are established. The silicon solubility is studied in wide ranges of temperature and Al–Ga melt composition. The results obtained are analyzed within the simple-solution model. Based on the experimental data on solubility, the parameters of interatomic interaction between components in the liquid phase are determined. The liquidus surface for the Si–Al–Ga ternary system is built in wide temperature and composition ranges. The results of studying the structural quality and electrical properties of recrystallized silicon layers are reported.

A distribution law of shortest distances to symmetry-equivalent surfaces in the form of a modified gamma-distribution has been derived for the crystal dissolution form in a multicomponent system. The technique of calculating the main morphological characteristics of crystal are demonstrated by the example of natural diamond of the Ural‒Brazil type. For simple crystallographic forms, which generate polyhedra characterized by topological variety, it is proposed to use the algorithm for calculating generalized polyhedra; using the latter, one can estimate the dissymmetrizing effect of environmental factors on a dissolving (or growing) crystal.

Ce³⁺,Nd³⁺:YAG single crystal was grown by Czochralski method without using any reduction gas. The growth was done in the atmosphere of pure nitrogen. The limited-flow of nitrogen gas was used for evacuating the produced oxygen in order to change Ce⁴⁺ to Ce³⁺ ions. The X-ray diffraction, absorption and luminescence spectrums were obtained from the sample of the grown crystal. The obtained results were discussed and compared with previously published data. The lattice parameter a = 12.001 Å was determined by the X-ray powder diffraction data. Distribution of the cores in a disc sample was studied. There was only one small central core in the sample.