Том 63, № 7 (2018)
- Жылы: 2018
- Мақалалар: 27
- URL: https://journals.rcsi.science/1063-7745/issue/view/12142
Diffraction and Scattering of Ionizing Radiation
Nanostructural Mechanism of Modifying Adaptation of Proteoglycan Systems of Biological Tissues and Mucus
Аннотация
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.
Crystallographic Symmetry
A Fuzzy Generating Set of 2D-Space Groups
Аннотация
Minimal Generating Subsets of Crystallographic Point Groups
Аннотация
All possible minimal sets of generating elements of crystallographic point groups have been derived. The variety of generating sets for each abstractly distinguishable group is presented in the form of a fuzzy generating set. The degree of fuzziness of generating set is calculated, and a cluster analysis of crystal classes with respect to the degree of fuzziness is performed.
Real Structure of Crystals
Structure and Properties of Syntetic Layered Lithium-Containing Silicates
Аннотация
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.
X-ray Interferometric Investigation of Strain Fields in Silicon Single Crystals
Аннотация
The dependence of the strain fields arising in the operating parts (units) of a silicon X-ray interferometer under mechanical impact on the dislocation density has been experimentally and theoretically investigated by the X-ray diffraction moiré topography. An X-ray interferometric method is proposed for high-accuracy determination of the elastic modulus of deformed crystal regions containing dislocations that were nucleated under an external impact. The elastic modulus is shown to decrease for a dislocation-containing crystal. The redistribution of the stresses occurring in the region of interferometer unit under study with a change in dislocation density has been investigated.
Structure of Inorganic Compounds
Refinement of the Crystal Structure of Vlasovite from Burpala Massif (Russia)
Аннотация
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% (Rw = 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) Å3, and Z = 4.
Deformation Mechanism of the LOSOD-Type Framework in Minerals of Bystrite Subgroup with a Change in Temperature and Chemical Composition
Аннотация
A Low-temperature (100 K) analysis of the crystalline structures of Cl-bystrite and sulfhydrylbystrite has been carried out, and the data obtained have been compared with the room-temperature characteristics of these minerals. The framework deformations are considered as a result of change in the ditrigonality of six-membered tetrahedral rings: the decrease in the unit-cell volume at low temperature is determined mainly by the increase in the ditrigonality (compression) of six-membered framework rings. Oblique and vertical (corrugated) rings are distorted to a greater extent than horizontal rings. The deformation mechanisms is shown to be the same for the frameworks of bystrite-subgroup minerals and the sodalite framework.
Crystal Structure of Bi1 – xPrxFeO3 Multiferroics at the Rhombohedral–Orthorhombic Phase Boundary
Аннотация
The crystal structures of Bi1 – xPrxFeO3 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 Bi1 – xPrxFeO3 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.
Structure of Organic Compounds
The Structure and Properties of 2,3-7,8-Dibenzpyrene-1,6-Quinone
Аннотация
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.
Crystal and Molecular Structure of 2-(4-Ethoxyphenyl)isoindoline-1,3-dione
Аннотация
The 2-(4-ethoxyphenyl)isoindoline-1,3-dione has been synthesized and characterized by X-ray single-crystal diffraction. The compound crystallizes in the orthorhombic sp. gr. Pna21 with four molecules in the unit cell and one molecule in the asymmetric unit. The molecular structure is not planar. The dihedral angle between the isoindoline and phenyl rings is 55.69(7)°. In the crystal structure, molecules are linked together by intermolecular C–H···O hydrogen bonds.
Synthesis and Structural Characterization of a Nickel Coordination Polymer Based on 4-(1H-Imidazol-1-yl)phenyl)methanone with Phthalic Acid
Аннотация
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.
Synthesis and Structural Characterization of a Cobalt Coordination Polymer with Bis(4-(1H-imidazol-1-yl)phenyl)methanone and 4-Nitrophthalate
Аннотация
A cobalt coordination polymer having the formula of [Co(npa)(L1)(H2O)2]n (1), where L1 is a bis(4-(1H-imidazol-1-yl)phenyl)methanone and H2npa is a 4-nitrophthalic acid, has been synthesized and structurally characterized. Single crystal X-ray diffraction analysis shows that the Co1 has a distorted octahedral geometry with four O atoms from two npa2– ligands and two N atoms from two L1 ligands, while the Co2 has the same coodination geometry with four O atoms from coordinating water molecules and two N atoms from two L1 ligands. Each L1 acts as a bridging ligand to link neighboring Co ions to form a 1D chain.
Synthesis and Structural Characterization of a Novel Cobalt Complex with (2E, 5E)-2,5-Bis(pyridin-3-ylmethylene)cyclopentan-1-one Ligands
Аннотация
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.
Molecular and Crystalline Structure of the Ruthenium(II) Complex [{trans-(dppe)2(Cl) Ru–C≡C–H} · 0.5CDCl3]: An Additional Determination
Аннотация
The synthesis and X-ray diffraction study of the ruthenium(II) complex, [{trans-(dppe)2(Cl) Ru–C≡C–H} · 0.5CDCl3] (trans-Ru · 0.5CDCl3), are presented. The molecule of trans-Ru · 0.5CDCl3 crystallizes in the triclinic sp. gr. \(P\bar {1}\) with two chemically equivalent but crystallographic independent molecules. The intramolecular C–H···Cl–C hydrogen bonds build with the deuterated chloroform. In addition, the intermolecular C–H···Cl–Ru hydrogen bonds have been also found.
Synthesis and Structural Characterization of the Schiff Base Zn(II) Complex from Salicylaldehyde and Tris(2-aminoethyl)amine
Аннотация
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.
Lattice Dynamics and Phase Transitions
Synthesis and X-Ray Study of K1 – хCsхNO3 (х = 0.015, 0.035) Crystals
Аннотация
K1 – хCsхNO3 (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.
Neutron Diffraction Study of the Phase Transformations in Titanium Carbohydride TiC0.50Hy
Аннотация
It is shown that the ordered phase of titanium carbohydride TiC0.50H0.31 with a face-centered cubic lattice (sp. gr. Fd\(\bar {3}\)m), obtained by self-propagating high-temperature synthesis, has an ordered antiphase domain structure with a period P = 16. This period is much larger than that in TiC0.50Hy (y ≤ 0.22), with a lower hydrogen content (P ≈ 11). It is shown that TiC0.50H0.31 decomposes at temperatures T ≤ 900°C into the cubic phase of titanium carbide TiCx (x ≥ 0.70) (sp. gr. Fm\(\bar {3}\)m) and the trigonal phase of titanium carbohydride Ti2Cv′Hz′ (sp. gr. P\(\bar {3}\)m1).
Determination of the Temperature Dependence of Lattice Parameters, Spontaneous Deformation, and Polarization in Ferroelectrics with Two Successive m3m–4mm–mm2 Phase Transitions
Аннотация
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.
Physical Properties of Crystals
Dielectric Relaxation and Conductivity of CdGa2S4 Single Crystal Grown by the CTR Method
Аннотация
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).
Dielectric Behavior and Conductivity of TlIn1 – xSbxSe2
Аннотация
TlIn1 – xSbxSe2 (x = 0–0.005 Sb) single crystals have been grown by the Bridgman method from polycrystals, which were synthesized from initial high-purity chemical elements (Tl, In, Sb, Se). The influence of antimony dopant on the dielectric properties and ac conductivity of TlIn1 – xSbxSe2 (x = 0–0.005 Sb) single crystals has been investigated. The experimental study of the frequency dispersion of the dielectric coefficients and conductivity of TlIn1 – xSbxSe2 single crystals has revealed the nature of dielectric losses (losses on through conductivity), establish the hopping charge-transfer mechanism, and estimate the parameters of the states localized in the band gap.
Anisotropy of the Refractive Indices and Thermal Expansion Coefficients of Rb2ZnCl4 Crystals
Аннотация
The temperature dependences of the optical path difference ∆і(Т) and relative changes δlі/lі in the thickness of Rb2ZnCl4 crystals have been studied. The temperature dependences of the relative changes in the refractive indices δnі/(nі – 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 Аn – 1(Т) are calculated. A characteristic minimum near the phase transition temperature is found in these dependences.
Surface and Thin Films
Laser-Induced Nanocluster Thin-Film Systems with Controlled Topology and Composition: The Possibility of Creating Superconducting Structures Based on New Physical Principles
Аннотация
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.
Crystal Growth
Determination of the Thermodynamic Parameters of Doping Silicon by Means of Thermomigration
Аннотация
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.
Effect of Crystallization Front Shape on the Dislocation Density in Germanium Single Crystals
Аннотация
The effect of crystallization front shape on the dislocation density in Ge single crystals with a diameter of 100 mm, grown by the Czochralski method, has been studied. The dislocation density in crystals with a convex crystallization front is found to be considerably higher. The average dislocation density in experimental ingots with deviation of crystallization front shape from flat in the range from –1.5 to +1.5 mm increases from 75 to 1000 cm–2 and from 75 to 700 cm–2 in the cases of convex and concave fronts, respectively. Minimum dislocation densities are observed for a flat or slightly concave front.
Model of Normal Crystal Dissolution
Аннотация
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.
New Cluster Concept of Crystal Formation
Аннотация
Some new models of crystal nucleation and growth, which make it possible to form fundamentals of nonclassical cluster paradigm of crystal formation, have been proposed within the theory of cluster self-organization of material on the nanoscale. According to these models, crystal nucleation occurs according to the two-step mechanism through the formation of peculiar nanoclusters (“hidden”-phase clusters or quatarons) in the crystal-forming medium. These clusters are also considered to be the main building units during crystal growth.
The Growth of Ce,Nd:YAG Single Crystal Under New Atmosphere Condition
Аннотация
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.