Vol 63, No 5 (2018)

A microfluidic cell has been developed for studying the structure of protein solutions using small-angle X-ray scattering. The use of prefabricated elements, which provide a small sample volume, allows one to adjust the microfluidic cell parameters to specific problems. Tests of lysozyme solutions were performed on a laboratory diffractometer AMUR-K (Institute of Crystallography, Russian Academy of Sciences), BM29 beamline (ESRF, Grenoble), and “DICSY” beamline of the Kurchatov synchrotron radiation source (National Research Centre “Kurchatov Institute”). Experiments showed that, when a 60-μm-thick quartz glass of special purity grade is applied as an X-ray-transparent window, the intrinsic level of cell background scattering in the range of measured angles is lower than that for quartz capillaries, due to which the measurement accuracy can be increased.

A technique for recording rocking curves using an X-ray optical bending element is proposed to study the changes in the defect structure of single crystals under external impacts. The technique has been approved for a silicon crystal under a uniaxial mechanical load.

High efficiency of the methods of double-crystal X-ray diffractometry (DCXRD) and topography for improving the growth technology of highly homogeneous crystals has been demonstrated on the example of gadolinium gallium garnet (GGG) single crystals. The main types of structural defects observed in Czochralski-grown GGG crystals are found to be macroscopic inhomogeneity of composition distribution, caused by the facet effect manifestation; microinhomogeneous distribution of impurity and main components of the composition in striations; dislocations; and second-phase inclusions. The relationship between the type and density of newly formed defects and the technological conditions for crystal growth are considered. Optimization of the composition of crystals and their growth technology made it possible to obtain high-quality dislocation-free crystals of GGG and complex-substituted garnets on its basis for magneto-optical and microwave devices, elements of solid-state lasers, and other applications.

Crystals of new indium iodate (K_0.6Na_0.4Ba)In[IO₃]₆ were prepared by the hydrothermal synthesis. The unit-cell parameters are a = 11.3984(3) Å, с = 11.3817(3) Å, sp. gr. R3̅. The chemical formula of the compound was derived from the structure determination and refinement with anisotropic displacement parameters to R = 0.0284. In the structure the InO₆ octahedra share vertices with six umbrella-like [IO₃]–groups typical of iodates and form isolated 3̅-symmetric charged \(\rm{In[IO_{3}]_6^{3-}}\) clusters. Large Ba, K, and Na cations occupy a common site on a threefold axis due to the isomorphous substitution and compensate the charge of the clusters. The new structure extends the family of the recently discovered alkali-metal and barium iodates containing Ti and Zr atoms in octahedral sites. The iodate K₂Ge[IO₃]₆ containing Ge atoms in the centers of octahedra is the parent compound of this structural family.

The morphology of the layer of polyelectrolyte complex, which is formed in the composite based on chitosan and sulfoethyl cellulose during the contact of a solution of one of them with a gel film of the other one, has been investigated by the low-voltage (≤3 kV) scanning electron microscopy. A technique for eliminating the effects related to charge accumulation on the dielectric film surface is proposed.

Different types of enzymes in rotational macromolecular motors of living cells are presented based on the data in the literature. Particular attention has been given to the restriction–modification enzymes and helicases, in which conformational changes in sites are physical reasons of linear motions and rotation of DNA molecules (caused by polar forces). It is shown that the structure and functioning of enzymes, similar to those in chiral smectic C-type liquid crystals, can be described within the formalism of generalized forces and currents. These forces include the membrane electrochemical gradient, the velocity of rotor mechanical motion, and the measure of change in free energy in the “fuel” adenosine triphosphate molecule.

Long-term changes in mechanical and electrical properties of p-type CdTe single crystals have been revealed after their exposure to a weak pulsed magnetic field (B = 1 T, ν = 12 Hz, t_exp = 10 min). A nonmonotonic increase in the hardness of crystals (presence of two peaks) and a nonmonotonic decrease in their specific dark conductivity (three peaks) have been observed. The peaks of changes in mechanical and electrical properties correlate on the time scale. It is shown that the intensity of observed effects depends on the crystal orientation with respect to the direction of magnetic induction vector B. In particular, the observed changes in properties for B || 〈111〉 are twice as large as those for B || 〈110〉. Possible mechanisms of the observed effect are discussed.

The products of interaction of SmF₃ with metallic Sm⁰, Si, and molecular hydrogen in quartz, graphite, and molybdenum containers have been investigated by X-ray diffraction. It is shown that reduction occurs with the formation of nonstoichiometric cubic SmF_{2 + x} (sp. gr. Fm3̅m, unit-cell parameter a = 5.8517(2) Å) with a content x = 0.108 only in the case of synthesis of SmF₃ with metallic Sm⁰ in a quartz ampoule. The transformation of the SmF_{2 + x} phase composition in air at room temperature has been studied for the first time. It is found that SmF_2.108 passes into the superstructural phase Sm₁₃F_32–δ (sp. gr. R3̅) with the unit-cell parameters a = 14.7354(4) Å and c = 10.1156(4) Å for 60 days. The use of Sm⁰, Si, and H₂ as reducing agents for SmF₃ is inefficient because of the weak tendency of the latter to reduction: the process occurs also with a low yield of the Sm₁₃F_32–δ phase and of the α-SmF₃-based phase as impurity in the case of direct reduction by hydrogen.

The spatial capacitance distribution, domain wall configuration, and impurity composition of triglycine sulfate TGS–TGS + Cr crystals with a growth periodic impurity structure have been investigated using scanning capacitance microscopy and X-ray fluorescence and topography. The chromium ion concentration in the strips emerging to the surface has been determined, and the periodic impurity distribution has been established. The difference between the chromium concentrations in nominally pure and impurity strips was found to be ~0.08 wt %, which is reflected in a variation in the capacitance image contrast by 0.17%. It is shown that capacitance images carry information about localization of the impurity gradient regions and domain walls and make it possible to establish a correlation between the defect and domain structures of a ferroelectric crystal.

The structure of diamond-like silicon–carbon films formed on silicon substrates by magnetron and plasmatron codeposition using a closed-field magnetron and a plasmatron activated by tungsten cathode has been studied by transmission electron microscopy. The main feature of the films alloyed by vanadium to concentrations of 12–31 at % was found to be a layered structure of the film cross section. It was established that vanadium alloying leads to the formation of vanadium carbide (VC) nanocrystals; the nanocrystal size increases from 1–2 to 10 nm. At the maximum vanadium content, VC nanocrystals have an anisotropic shape: they are extended in the direction perpendicular to the film–substrate interface.

Proton-conducting composites xCs₄(HSO₄)₃(H₂PO₄) + (1–x)AlPO₄ in the composition range x = 0.9–0.5 have been obtained. Their transport properties are studied by impedance spectroscopy. The dependences of the phase composition of the materials on the component ratio are investigated by X-ray diffraction analysis. The spatial phase distribution in the materials is analyzed using scanning electron microscopy.

The structures of one-dimensional (1D) RbI, AgI, and RbAg₄I₅ crystals inside single-walled carbon nanotube (SWCNT) channels of 1D crystal@SWCNT nanocomposites formed by the capillary technique have been studied by high-resolution (scanning) transmission electron microscopy and computer modeling. 1D RbI crystals form a cubic lattice in a limited space, while 1D AgI crystals form a hexagonal lattice, as in their ternary compounds. The 1D RbAg₄I₅ structure differs from known bulk analogs and can be described by a distorted cubic lattice formed in two different directions.

Samples of single-crystal plates of p-terphenyl (3Р) and its derivative with terminal substituents–Si(CH₃)₃ (TMS-3P-TMS), up to 25–30 mm in size and 400 μm thick, have been obtained for the first time by the solvent–antisolvent growth method. The crystal structure at temperatures of 293 and 85 K is refined for 3Р and solved (for the first time) for TMS-3P-TMS using X-ray diffraction. The habit of crystals and their surface morphology are investigated by methods of optical and laser confocal microscopy. The influence of substituent terminal groups -Si(CH₃)₃ on the growth and structure of TMS-3P-TMS crystals is analyzed based on experimental data. The optical absorption and photoluminescence spectra of solutions and crystalline samples are investigated.

Proceeding from the phase diagram of the CaF₂–SrF₂ system, the stability of crystal–melt interface of solid solution against constitutional supercooling has been calculated. When comparing the stability function F(x) calculated curve with the results of single crystals growing by the Bridgman method, the interdiffusion coefficient of cations in melt was estimated to be D > 2.4 × 10^–4 cm²/s.

Fragments of ancient amphorae and tiles dated to the IVth to IInd centuries BC, which were found on the Crimean peninsula, have been investigated by methods of scanning and transmission/scanning electron microscopy, combined with energy-dispersive X-ray microanalysis. The revealed differences in the compositions of the clay core and inclusions (leaners) are associated with the differences in the periods of time when items were made and the sites of their origin.