New Data on the Isomorphism in Eudialyte-Group Minerals. III: Modular Structure of K Analog of Centrosymmetric Labyrinthite

Crystallography Reports - The crystal structure of a new modular eudialyte-group mineral from the Khibiny massif—potassium-rich analog of labyrinthite—has been investigated using X-ray...     

New Data on the Isomorphism in Eudialyte-Group Minerals. IV: Modular Structure of Titanosilicate with Replacement of Na by Mn in the Alluaivite Module

Crystallography Reports - A new modular eudialyte-group mineral—titanosilicate—from the Lovozero massif has been investigated using X-ray diffraction. The trigonal-cell parameters are...     

Diophantine laws for nets of the highest symmetries

The theoretical-numerical properties of the square and the hexagonal nets are presented as well as their characteristic triads of integers—the Denis numbers—applicable to the practical X-ray diffraction analysis of single crystals.     

Methods of chemical and phase composition analysis of gallstones

This review presents the instrumental methods used for chemical and phase composition investigation of gallstones. A great body of data has been collected in the literature on the presence of elements and their concentrations, obtained by fluorescence microscopy, X-ray fluorescence spectroscopy, neutron activation analysis, proton (particle) induced X-ray emission, atomic absorption spectroscopy, high-resolution gamma-ray spectrometry, electron paramagnetic resonance. Structural methods—powder X-ray diffraction, infrared spectroscopy, Raman spectroscopy—provide information about organic and inorganic phases in gallstones. Stone morphology was studied at the macrolevel with optical microscopy. Results obtained by analytical scanning and transmission electron microscopy with X-ray energy dispersive spectrometry are discussed. The chemical composition and structure of gallstones determine the strategy of removing stone from the body and treatment of patients: surgery or dissolution in the body. Therefore one chapter of the review describes the potential of dissolution methods. Early diagnosis and appropriate treatment of the disease depend on the development of clinical methods for in vivo investigation, which gave grounds to present the main characteristics and potential of ultrasonography (ultrasound scanning), magnetic resonance imaging, and X-ray computed tomography.     

Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°С, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid and liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.     

Defects of different sizes in large paratellurite single crystals

Paratellurite single crystals have good acoustooptical properties that are important for various devices, such as deflectors, modulators, and tunable noncollinear filters. Paratellurite single crystals of up to 80 mm in diameter and 100 mm in height were grown using the Czochralski method from ultrapure melts. Optical anomalies in the grown crystals—gas bubbles, striations, impurity inclusions with nearby stresses, and regions with high dislocation densities—were studied with chemical, X-ray, and optical methods.     

Synthesis and Crystal Structure of NdCaGaO4

The crystal structure of the NdCaGaO₄ compound was investigated by means of X-ray structure analysis (powder diffractometer HZG-4, CuK_α): structure type LaCuO₄, space group Cmca, a = 5.3700(2) Å, b = 12.1058(3) Å, c = 5.3937(2) Å, Z = 4, R_I = 0.126. The shortest interatomic distances are: Nd(Ca)—O — 2.240(14) Å; Ga—O — 1.913(2) Å, O—O — 2.6852(2) Å, Nd(Ca)—Nd(Ca) — 3.442(3) Å, Nd(Ca)—Ga — 3.154(4) Å, Ga—Ga — 3.8056(2) Å. Atoms have the following coordination numbers: Nd(Ca) — 8; Ga — 6; O1 — 14(6); O2 — 9(5).     

Structural and Electrical Characterization of Ag3Ga5Te9 and Ag3In5Se9 Crystals

X-ray powder diffraction studies revealed that Ag₃Ga₅Te₉ and Ag₃In₅Se₉ crystallize in orthorhombic and tetragonal systems, respectively. The temperature dependent conductivity and Hall effect measurements have been carried out between 65—480 K. Ag₃Ga₅Te₉ exhibits p-type conduction with a room temperature conductivity of 4.3 × 10^—4 (Ω · cm)^—1 and mobility less than 1 cm²/V · s. Ag₃In₅Se₉ was identified to be n-type with room temperature conductivity 7.2 × 10^—5 (Ω · cm)^—1 and mobility 20 cm²/V · s. From temperature dependence of the conductivity three different impurity ionization energies were obtained for both compounds. The anomalous behavior observed in the temperature dependence of mobility was attributed to the different features of the microstructure.     

磷掺杂介孔碳的制备及其电化学性能

以酚醛树脂为碳前驱体,磷酸为磷源,三嵌段共聚物F127为软模板,通过溶剂挥发诱导自组装(EISA)法制备了具有介孔结构的磷掺杂介孔碳(PMCs)。通过场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等测试方法研究所制备的PMCs的形貌与结构并利用电化学工作站测试其电化学性能。实验结果表明,磷元素在介孔碳中主要以C—P键和P—O键两种形式存在。电化学测试表明,通过调整磷掺杂量可获得最大比电容。当电流密度为0.5 A/g时,介孔碳比电容为140 F/g,而优化后的磷掺杂介孔碳比电容可达176 F/g。     

Crystal Structures of Methyl and Ethyl N-(2,3-Dimethoxybenzyl)-N-(p-toluenesulfonyl)-2-phenylglycinates

The crystal structures of methyl and ethyl N-(2,3-dimethoxybenzyl)-N-(p-toluenesulfonyl)-2-phenylglycinates 4a and 4b respectively, have been determined by X-ray diffraction analysis. The presence of different alkyl ester groups in both molecules does not affect the geometry retaining a synclinal conformation for the N atom and the O atom of the C=O group [N—C17—C18—O5 38.1(5)° for 4a and 33.3(4)° for 4b ].     

Insights into Biaxial Ordering of Bent-Core Nematics: X-Ray Diffraction Evidence

Recently we have reported the first X-ray diffraction evidence of biaxial order in the fluid cybotactic nematic phase of a pair of trimethylated bent-core mesogens. This evidence is based on the splitting of the wide-angle diffuse scattering in the plane normal to the nematic director. The additional experimental data presented here provide further insights into this unprecedented behavior observed over the entire nematic phase. Although we could not determine the spatial extent of biaxial order—intracluster or intercluster—our observations reveal an enhanced biaxial orientational correlation in the transverse molecular packing, possibly reflecting stronger anisotropic interactions between nearest-neighbor mesogens.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.     

Approximation of local reflection in meridional schemes of Bragg focusing

The wave amplitudes in the vicinity of the focus in monochromatic focusing are calculated in the approximation where each point of the surface of a weakly bent single crystal reflects an X-ray wave as a planar crystal, while the reflection coefficient is a coordinate function of the deviation from the exact Bragg condition. These amplitudes are calculated for all the meridional diffraction geometries (those for plane and spherical waves and the Johann and aberration-free schemes). For all these schemes, the quantitative characteristic of the process of polychromatic focusing—the intensity integrated over the pass band—is introduced and calculated. The analytical expressions of polyprofiles necessary for the consideration of these schemes are also derived.     

Photoemission Studies of Ultrathin Sn-Layers on TiO2—x (rutile)

A clearly reduced (111) surface of a rutile single crystal was coated in situ with monolayers of tin and investigated using soft X-ray photoelectron spectroscopy of core levels. Tin grows as an oxide in the first monolayer accompanied by a further reduction of TiO_2—x and in metal state for higher coverages.     

Small-angle x-ray scattering study of polymer structure: Carbosilane dendrimers in hexane solution

The three-dimensional organization of monodisperse hyper-branched macromolecules of regular structure—carbosilane dendrimers of zero, third, and sixth generations—has been studied by small-angle X-ray scattering (SAXS) in solution. The use of modern methods of SAXS data interpretation, including ab initio modeling, has made it possible to determine the internal architecture of the dendrimers in dependence of the generation number and the number of cyclosiloxane end groups (forming the shell of dendritic macromolecules) and show dendrimers to be spherical. The structural results give grounds to consider carbosilane dendrimers promising objects for forming crystals with subsequent structural analysis and determining their structure with high resolution, as well as for designing new materials to be used in various dendrimer-based technological applications.     

New oxygen-and lead-deficient lead borate Pb 0.9 (I) Pb 0.6 (II) [BO2.25]2 = 2Pb0.75[BO2.25] and its relation to aragonite and calcite structures

Anhydrous oxygen-and lead-deficient lead borate of the composition Pb _0.9 ^(I) Pb _0.6 ^(II) [BO_2.25]₂ = 2Pb_0.75[BO_2.25] (sp. gr. P312) has been obtained by the hydrothermal synthesis. New acentric borate possesses optical nonlinearity comparable with the optical nonlinearity of α-quartz. The crystal structure of new borate is determined and refined by two X-ray diffraction methods—the single crystal diffractometry and the full-profile analysis. All the positions in the structure, except for those of the boron atom in the triangular coordination, are occupied only partly; one of the two lead positions is split. It is established that new borate is closely related to calcium carbonates—aragonite, calcite, and paralstonite. With an increase of the temperature, new borate undergoes the reversible phase transition into the centrosymmetric, most probably, aragonite-like phase.     

A new supramolecular cocrystal of 2-amino-3-bromopyridine with 4-methylbenzoic acid: Synthesis,structural, spectroscopic characterization and comparative theoretical studies

The 1:1 cocrystal of 2-amino-3-bromopyridine (2A3BP) with 4-methylbenzoic acid (4MBA) has been prepared by slow evaporation method in methanol, which was crystallized in monoclinic P2₁/c space group having two molecules in the asymmetric unit. The cocrystal has been characterized by single crystal X-ray analysis, FTIR, ¹H NMR, ¹³C NMR, and Powder XRD. Theoretical investigations have been calculated by HF and density function (B3LYP) method with the 6-311+G(d,p) basis set. The vibrational frequencies together with the ¹H NMR and ¹³C NMR chemical shifts have been calculated on the fully optimized geometry of 1. Theoretical calculations of bond parameters, harmonic vibration frequencies, and isotropic chemical shifts are in good agreement with the experimental results. Solvent-free formation of these cocrystal was confirmed by powder X-ray diffraction analysis. The crystal structure was stabilized by N_pyridine—H···O = C, C = O—H···N_pyridine and C—H···Br hydrogen bonding interactions.     

The Crystal and Molecular Structure of 4'-Cyanophenyl-4-n-Pentylbenzoate

The crystal and molecular structure of the title compound with the formula C₅H¹¹—C₆H₄—COO—C₆H₄—CN (CPPB) has been determined by X-ray diffraction methods. CPPB crystallizes in the monoclinic space group P2₁/n with eight molecules in a unit cell of dimensions a = 15.268(2) Å, b = 9.165(1) Å, c = 24.031(3) Å, β = 94.67(1)°. The structure has been solved by direct methods and refined to an R value of 0.070.

The CPPB molecules adopt a stretched form and are packed in an approximate parallel imbricated mode, the molecular long axes making an angle of about 5° with the crystal c axis. The molecular geometry and packing are discussed in relation to the mesomorphic behavior of CPPB.     

基于有机羧酸配体的Co(Ⅲ)/Cu(Ⅱ)配合物的合成、结构及表征

在溶剂热条件下,以含卤素有机羧酸3-溴-吡啶-2,6-二甲酸(H₂L)为配体,以硝酸钴、硝酸铜为金属源,合成了两例配合物:[Co(L′)₃](1)和[Cu(L′)₂]_n(2)(HL′=5-溴-吡啶-2-甲酸),通过元素分析(EA)、X射线单晶衍射(SXRD)、X射线粉末衍射(PXRD)、红外光谱(IR)和热重分析(TGA)进行结构表征。X射线单晶衍射结果表明,配体H₂L在反应过程中发生脱羧现象,生成单羧酸配体5-溴-吡啶-2-甲酸。在配合物1中,每个Co(Ⅲ)都位于略微扭曲的八面体几何构型中,不对称单元中含有两个单核单元,单核单元通过C—H…O氢键形成三维超分子结构。配合物2的不对称单元中含有一个Cu(Ⅱ),两个脱质子的L′^-配体,每个Cu(Ⅱ)都是六配位的,位于扭曲的八面体几何构型中。Cu(Ⅱ)由配体连接生成1D链结构,通过C—H…O氢键形成三维超分子结构。此外,研究了两例配合物的热稳定性能。