Crystallography Reports最新文献

The elemental composition and manufacturing technology of the so-called Sarmatian-type mirrors have been studied. The investigated mirrors are random finds, originating from the territory of the Kerch peninsula. All three objects are pendant mirrors with a radial-beam ornament that appeared at the turn of the 1st and 2nd centuries AD; they were in use until the beginning of the 3rd century AD. According to the results of X-ray fluorescence analysis, the mirrors were made of a material with identical qualitative characteristics: an alloy of copper, tin, and lead. X-ray tomography clarified the details of the relief ornament, which is weakly pronounced on the products due to corrosion processes.

The structure and defects of α-TeO₂ paratellurite crystals have been studied using computer modeling. It has been shown that the preferred point defects in α-TeO₂ are oxygen vacancies and interstitial oxygen ions. Oxygen vacancies can either be isolated or form complex clusters. It is energetically most favorable for interstitial oxygen ions to be located in channels that penetrate the paratellurite structure along the c axis. The origin of possible oxygen-ion transport in α-TeO₂ is discussed.

The maximum possible number of TE- and TM-polarized surface plasmon polaritons in the forbidden band of the Bloch spectrum of electromagnetic waves of a periodic superlattice in structures containing a metal film between a homogeneous medium and a periodic superlattice or between two superlattices has been established. It is shown that the key role in determining the maximum number of these waves is played by the type of the frequency dependence of the superlattice impedance. In addition, the maximum number of solutions of surface plasmon polaritons depends on the structure type and the wave polarization.

The synthesis of a complex compound based on divalent copper as a complexing agent and 1,10-phenanthroline and nitrate ion as ligands has been described for the first time. The obtained complex, being linked with mandelic acid by hydrogen bonds, associates it in the external sphere. The interest in these ligands is caused by their potential biological activity and possibility of using them in pharmaceutics. The composition of the synthesized metal complex is found to be [Cu(1,10-phen)₂NO₃](C₈H₈O₃⋅NO₃), as confirmed by elemental analysis. The molecular and crystal structures of the complex are studied by X-ray diffraction (XRD). Its crystallographic characteristics, bond angles, lattice parameters, and geometry of hydrogen bonds are determined. The data obtained made it possible to construct a 3D model of the material. A Hirshfeld surface analysis of the metal complex, performed using the Crystal Explorer program, showed the presence of hydrogen bonds in it, which stabilize its crystal structure.

The process of high-temperature oxidation of silicon carbide-based ceramic materials synthesized by spark plasma sintering without any sintering-activating additives has been studied. Analysis of the microstructure of the oxidized ceramic samples and the data on the change in their mass indicate the formation of a protective SiO₂ layer on the SiC surface, which is characteristic of passive oxidation of silicon-containing oxygen-free compounds. The results of the comparative study of oxidation of the SiC ceramic samples with different porosity in air at a temperature of 1200°C have revealed a linear relationship between the growth rate of the oxidized sample mass and the volume of open pores in the sample.

A re-study of the crystal structure of low-calcium and high-zirconium eudialyte from the Khibiny Mountains of Kola Peninsula has revealed new features of its structure, which decrease the symmetry of the mineral. The ordering of Ca, Fe, Mn, and Na atoms in octahedra of six-membered rings, as well as Zr and Na atoms in M2 positions at the centers of square pyramids, with a common base, formed by the edges of these octahedra, has been established with the P3 symmetry. The trigonal unit cell parameters are a = 14.222(3) Å, c = 30.165(5) Å, and V = 5283.9 ų. Taking into account the new data, the studied low-calcium eudialyte can be assigned to the subtype of oneillite or raslakite, being a high-zirconium variety of the latter. The study of the structure of this mineral in rhombohedral symmetry (sp. gr. R3m and R3) and trigonal Р3 symmetry has shown that the decrease in symmetry of the structural model of low-calcium representatives of the eudialyte group makes it possible to clarify the nature of ordering of the cations occupying key framework positions.

Based on comprehensive studies of fragments of antique red-glazed pottery (terra sigillata) of the Pontic, Bosporan, and Eastern groups, characteristic technological features of the slip layer and ceramic bulk have been identified. The Eastern-sigillata samples exhibited the best quality. The small size of the pores and inclusions suggests the use of finely dispersed clay. In addition, a mixture of two types of clay (ferrous and more refractory calcareous) was revealed. The special and, apparently, careful preparation of the clay suspension for the slip layer production included addition of a potassium-containing preparation, presumably, potassium potash (to glaze better the layer), as well as an iron-containing pigment, likely, ochre. The firing temperature for this group of samples was about 1000°C. Pontic sigillata products differed from the Eastern pottery by a lower content of potassium potash and the absence of specially added pigment in the varnish layer. The firing temperature was lower: 850–900°C. The Bosporan products are characterized by much less thorough preparation of both the clay raw material as a base and the varnish layer, as well as the lowest firing temperature in comparison with other groups (500–900°C).

Samples of self-assembled particles based on the capsid protein of bacteriophage MS2 were obtained using different purification protocols and characterized. The study demonstrates the feasibility of using a combination of electron microscopy and small-angle X-ray scattering (SAXS) to select the optimal purification protocol. Electron microscopy allows the evaluation of self-assembly, while SAXS helps to estimate the statistical distribution of particles of different shapes and sizes in a sample. The best results were obtained using the PEG precipitation in combination with gel filtration and ultrafiltration.

The interaction of the ectodomain of the human coronavirus spike protein with the phospholipid monolayers formed on the aqueous subphase surface has been investigated. The changes in the molecular organization of monolayers of two neutral phospholipids—dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylethanolamine—after the injection of a protein solution underneath the monolayer have been analyzed. Experiments were performed with a recombinant ectodomain of the S-protein, expressed in a CHO-K1 cell strain. Electron microscopy data showed that the protein is trimerized. Grazing incidence diffraction measurements were performed to study the influence of the trimer ectodomain of the S-protein on the structure of the dipalmitoylphosphatidylcholine monolayer. It is found that protein injection under the monolayer does not induce disturbance of the monolayer crystal structure. The experimental results obtained in X-ray studies and compression isotherm measurements indicate that the interaction with the S-protein does not result in destabilization of the monolayer for both phospholipids.

SiC and TiC samples have been obtained by spark plasma sintering. The SiC ceramics samples have the main phase 6H-SiC (α-SiC) and low contents of SiO₂ and 16H-SiC phases. Raman spectroscopy has shown the presence of free unbound carbon in them and a lower structural quality of the surface layer. The samples exhibit microhardness values typical of ceramics with similar porosity values. In turn, the TiC sample is characterized by low porosity, a uniform composition of cubic TiC phase, a small amount of free carbon, and a microhardness typical of TiC alloys. The results obtained allow one to speak about the applicability and prospects of the spark plasma sintering method in the synthesis of functional ceramics.