Crystallography Reports最新文献

Digital processing of the 2D noisy X-ray diffraction images (2D-XDI) of a single point defect in a Si(111) crystal, recorded at the level of dispersion of statistical Gaussian noise of the detector using filtering methods, such as singular value decomposition and 1D-line-by-line smoothing of test 2D-XDI, is carried out. The efficiency of digital filtering of 2D-XDI is evaluated and analyzed by means of the control parameter FOM (figure-of-merit) value of reconstruction of the displacement field function of a point defect of Coulomb type f_h(r – r₀), (h is the diffraction vector, r₀ is the radius-vector of the defect position in the sample). It is shown that the filtering technique using the singular value decomposition of 2D-XDI works much better than the 1D line-by-line smoothing method of 2D-XDI, which, apparently, as applied to our problem, requires further research for its improvement.

The metal-organic polymer MIL-53(Fe) with the framework composition Fe(OH)(BDC)⋅(H₂O)₂ and the composite MIL-53(Fe)/GO (GO is graphene oxide) have been obtained by the solvothermal method and characterized by X-ray diffraction, X-ray absorption spectroscopy, IR Fourier spectroscopy, and scanning and transmission electron microscopy. It has been established that the MIL-53(Fe) in the MIL-53(Fe)/GO composition differs from the initial MIL-53(Fe) polymer by the absence of secondary phase (phases), a lower content of water molecules, a higher content of the solvent and Fe²⁺ ions, and the morphology and microstructure. In the photo-Fenton reaction, the degree of decomposition of RR195 dye in the presence of the MIL-53(Fe)/GO composite exceeds the degree of decomposition of the initial MIL-53(Fe) polymer, which remains almost invariable after three photo-reaction cycles.

The new bis(2,6-diaminopyridinium) tetrachlorozincate complex of the composition (С₅Н₈N(_{3}^{ + }))₂[ZnCl₄]^2– was synthesized by the reaction of 2,6-diaminopyridine with a Zn(II) ion in an ethanolic solution of hydrochloric acid. The composition and the molecular and crystal structure of the synthesized complex were determined by X-ray diffraction analysis. The composition of the metal complex was confirmed by elemental analysis. The chemical bonds were investigated by IR spectroscopy. Intermolecular interactions in the crystal were studied by the Hirshfeld surface analysis. The stability of the complex was determined by thermal analysis and it is, apparently, attributed to intramolecular hydrogen bonds.

The anthropogenic calcium fluorosilicate “kutyukhinite” Ca₅[SiO₄]₂F₂ from burnt dumps of the Chelyabinsk coal basin has been studied by single crystal and powder X-ray diffraction analyses in a wide temperature range. “Kutyukhinite” (P2₁/a, a = 11.4985(4) Å, b = 5.0535(2) Å, c = 8.7848(3) Å, β = 109.008(4)°, V = 482.63(3) ų, R₁ = 0.0183) is an anthropogenic analogue of kumtyubeite, which belongs to the structural type of chondrodite. The empirical formula of “kutyukhinite” is Ca_5.02[Si_1.99O_7.98]F_2.04. Upon heating, its crystal structure expands anisotropically, with the direction of maximum thermal expansion close to the [100] direction. The relative change in bond lengths in silicon–oxygen tetrahedra with increasing temperature (27–927 °C) is less than 0.6%, which is within the margin of error. At the same time, the relative increase in the average bond length 〈Ca–O〉 varies from 1% (〈Ca1–O〉) to 1.5% (〈Ca3–O〉). The largest relative change of  2% was found for the average bond length 〈Ca3–F1〉.

Crystals of hydrogen-containing compounds Cs₄(HSO₄)₃(H₂PO₄) and NH₄Cl⋅2H₂SeO₃ have been studied using the neutron diffraction methods implemented at the comissioned experimental single-crystal neutron diffraction station (MOND) installed on the thermal neutron beam of the IR-8 reactor of the National Research Centre “Kurchatov Institute.” The obtained results demonstrate the capabilities of the techniques for localizing hydrogen atoms with high accuracy and characterizing hydrogen-bonded systems, the information about which is necessary for establishing correlations between the atomic, real structure and the physico-chemical properties of the investigated crystals.

The phase formation in the system of triple phosphates Sr–M²⁺–Ln³⁺ (M²⁺ = Zn²⁺, Mg²⁺, Mn²⁺; Ln³⁺ = Eu³⁺, Tb³⁺) is considered. Specific features of the strontiowhitlockite phase formation and the isomorphism in the series of phosphates Sr(_{{9-x}})Mn_xTb(PO₄)₇, Sr(_{{9-x}})Mg_xEu(PO₄)₇, and Sr(_{{9-x}})Zn_xEu(PO₄)₇ (0 ≤ x ≤ 1.0), obtained by solid-phase synthesis, have been studied. It is shown that a continuous series of solid solutions of these compositions cannot be formed. Crystallization of phases with strontiowhitlockite-type structures is observed for only stoichiometric phosphates Sr₈MgEu(PO₄)₇ and Sr₈ZnEu(PO₄)₇. Crystal chemical analysis of the possibility of strontiowhitlockite phase formation in the studied series is performed. It is shown that samples with the strontiowhitlockite structure crystallize in the centrosymmetric space group (sp. gr. R(bar {3})m), in contrast to the mother structure of mineral whitlockite and its calcium-based synthetic analogues. The conditions for the formation of phosphates with the stronciowhitlockite structure are indicated. The photoluminescence properties have been investigated. It is shown that the samples exhibit stable photoluminescence in the red-orange region due to the emission of Eu³⁺ cations, whereas a quenching effect is observed in the Sr(_{{9-x}})Mn_xTb(PO₄)₇ series.

Crystals of lead monochloroacetate, Pb(ClCH₂COO)₂, were obtained in the reaction of lead carbonate and aqueous chloroacetic acid. The compound crystallizes in the monoclinic system (space group P2₁/c) with the unit-cell parameters a = 10.8346(6) Å, b = 7.7239(4) Å, c = 10.1484(5) Å, β = 106.542(5)°. Like in other medium- and long-chain lead carboxylates, the crystal structure of lead monochloroacetate is layered. Lead atoms are located in distorted seven-vertex PbO₇-polyhedra, which share edges and form layers. Features of the crystal structures of lead salts of carboxylic acids with unbranched hydrocarbon radicals are discussed. In particular, salts of lead(II) n-alkyl carboxylates with the general formula Pb(C_nH(_{{2n + 1}})COO)₂, despite belonging to different symmetry and space groups (monoclinic P2₁/m for n = 2 and 3, triclinic P(bar {1}) for n = 4–9, and monoclinic P2₁/c for Pb(ClCH₂COO)₂), are characterized by the same arrangement of molecules, so they can be considered structurally related.

Data on the synthesis of double borates crystallizing in the BaO–Lu₂O₃–B₂O₃ system and Eu³⁺-activated phosphors based on them, as well as on the finding of correlations between their chemical composition, crystal structure, and thermal and optical properties are presented. Based on the results of the investigation of all currently known double Ba–Lu borates, it is shown that search for novel compounds in this system, as well as the development of optical materials on their basis, is a promising direction in the field of creating new functional materials for LED applications.

The TE- and TM-polarized surface plasmon polaritons in a metal film contacting a semi-infinite periodic superlattice formed by alternating layers of two materials have been theoretically investigated. It is shown that, in a certain case, the frequency dependence of the impedances of this bilayer superlattice can be of only two types out of three possible types of dependences. The dispersion curves of ТE- and TM-polarized surface plasmon polaritons in a silver film have been calculated for a number of structures consisting of various combinations of bilayer superlattices containing quartz and titanium oxide layers. The calculation results are compared with the conclusions of the general theory on the maximum number of surface plasmon polaritons. The effect of the absorption of electromagnetic waves in the film on the characteristics of surface plasmon polaritons is analyzed.

Crystals of new double sulfates (dmedaH₂)[Co(H₂O)₆](SO₄)₂ (1) and (dmedaH₂)[Ni(H₂O)₄(SO₄)₂] (2), as well as (dmedaH₂)₂(SO₄)₂⋅3H₂O (3), where dmeda is N,N'-dimethyl-ethylenediamine, were obtained by isothermal evaporation. The compounds crystallize in the triclinic symmetry, space group P(bar {1}), while compound 3 is characterized by the orthorhombic symmetry with the space group P2₁2₁2₁. The crystal structure of 1 contains isolated octahedral cations [Co(H₂O)₆]²⁺ and ({text{SO}}_{4}^{{2 - }}) tetrahedra, while the crystal structure of 2 contains complex anions trans-[Ni(H₂O)₄(SO₄)₂]^2–. Structures of 1 and 2 are compared with the structures of double cobalt and nickel sulfates with ethylenediammonium, where the opposite case is observed. The formation of both aqua- and aquasulfate complexes is quite typical for cations of transition metals of the 3d series. While for double sulfates of transition metals with inorganic cations the hydration number depends to a greater extent on the synthesis temperature and the ionic radius of the monovalent metal, for double sulfates with organic cations the picture is more complex. The crystal structure of compound 3 can also be considered as pseudolayered, with the cationic layer formed only by the organic component, while the anionic layer also includes water molecules. The anionic layer contains cavities, the volume of which allows us to assume that, under certain conditions, they can be occupied by water molecules, which would correspond to the composition (dmedaH₂)(SO₄)⋅2H₂O. Topological analysis of the obtained compounds showed that metal complexes with ethylenediammonium demonstrate a relatively high structural complexity of H-bonds with a lower complexity of structural units, as compared to N,N'-dimethylethylenediammonium.