Crystallography Reports最新文献

The phase transition in composites based on polyvinylidene fluoride and cobalt ferrite nanoparticles under uniaxial stretching at 100, 200, and 300% has been investigated. It was found that, when the composite is stretched at 300%, there is a maximum increase in the β-phase fraction: from 1% for the unstretched sample to 91%, while the fraction of the electrically active phase increases from 74 to 92%. It was also established that tensile stretching of the composites leads to an increase in the tensile strength: from 5.7 to 85.0 MPa. This tensile pattern also contributes to the increase in coercivity, which is due to the increase in the interparticle distance in the composite structure. These results emphasize the importance of the mechanical properties and phase changes in ferrite-containing polymer composites for their future applications.

An additive model has been developed for calculating the combinatorial (Shannon-like) complexity of the signature of a natural tiling, which is used to describe the topological properties of micro- and mesoporous materials, in particular, zeolites. To calculate the complexity of this type, a Python program code has been compiled. The code was tested for zeolite-type tilings. Correlations of the calculated complexity of the signature of the tiling and the combinatorial complexity of the structure-generating tiling were found.

The effect of the imperfections of the polarizer, analyzer, and photomultiplier tube (PMT) on the results of measuring the spectral transmission dependences of catangasite (Ca₃TaGa₃Si₂O₁₄) crystals cut perpendicular to the optical axis has been theoretically and experimentally investigated. There is a difference between the spectra obtained for the p and s polarizations of incident light; jumps are also observed on the curves at λ = 1050 nm. This is due to the imperfection of the PMT and the optical activity of the crystal. The PMT parameters are estimated in dependence of the light wavelength proceeding from experimental data. The influence of the imperfection of the PMT and polarizers on the results of calculating the rotation of the plane of polarization ρ is studied. It is shown that transmission spectra must be measured at angles between the polarizer and analyzer of ±45° in order to to calculate exactly the ρ value. The measurement errors are determined by the set of optical elements in a particular device.

The structure and properties of sanmartinite ZnWO₄ have been simulated by the method of empirical interatomic potentials. A system of coordinated interatomic potentials has been developed, which makes it possible to describe the structural, elastic, and thermodynamic properties of zinc tungstate and simulate more complex composite media containing this component.

The crystal structures of the epitaxial multilayer films {In_0.1Ga_0.9As/GaAs} × 10 and {In_0.2Ga_0.8As/GaAs} × 10 grown on GaAs substrates with different orientations, (100), (110), and (111)А, were studied in order to elucidate specific features, which can be related to the previously found efficiency of the terahertz emission generation in films with (110) and (111)А orientations. Significant concentrations of twins and stacking faults were found on non-standard GaAs (110) and (111)А substrates. The composition and thickness of individual layers of heterostructures on GaAs (100) substrates were refined based on the analysis of interference oscillations in X-ray diffraction curves.

The specific features of the ion transport in paratellurite α-TeO₂ crystals under an external dc electric field have been investigated by the molecular dynamics method. It is shown that the ion transport anisotropy is more pronounced when the field E is directed along the c axis: at E = 350 kV/mm the diffusion is enhanced by a factor of about 2 in crystals with oxygen vacancies and by a factor of 3 in samples with additional oxygen interstitials.

The basic composition of polychrome enamels of three bronze items, found on the territory of Vladimir and Suzdal Opolye (a temporal pendant, a pendant icon, and a cross), dating from the 12th–13th centuries, has been studied by atomic emission spectroscopy and energy-dispersive X-ray microanalysis. The items have a rich color, which made it possible to investigate the technological features of a wide range of colored enamels: white, black, gray, light gray, deep blue, red-brown, brown, green, blue-green, turquoise, and yellow. The obtained results suggest the Byzantine origin of the enamels and local production of the items themselves.

The effect of the imperfections of the polarizer, analyzer, and photomultiplier tube (PMT) on the results of measuring the spectral transmission dependences for langasite family crystals cut parallel to the optical axis has been theoretically and experimentally investigated. It is shown that, in the absence of analyzer, oscillations arise on the transmission spectra, whose amplitude depends on the crystal rotation. These oscillations are associated with linear birefringence and occur because of the imperfection of the PMT, which plays the role of a partial analyzer. The PMT parameters in dependence of wavelength are calculated from the obtained spectra. The birefringence of the studied crystals was calculated, and the error of this calculation was estimated. It is shown that the imperfection of optical elements does not lead to any additional errors in the calculation of the birefringence. Thus, when the plate is cut perpendicular (parallel) to the optical axis, circular (linear) birefringence manifests itself.

A technique for forming true distributions of  X-ray diffraction intensity using X-ray diffractometry has been developed to reveal inhomogeneous deformations of a curvilinear surface with a periodic relief by separating the effects related to the influence of this surface on the diffraction profile shape. True intensity distribution profiles, related to only inhomogeneous surface deformations and sizes of crystalline blocks, were obtained; the parameters and specific features of the distribution functions of these deformations were determined. The proposed approach makes it possible to select, in particular, the contribution from only a curvilinear surface with a regular sample relief to the shape of the intensity distribution profile.

The reflectance of medium-energy (~10 KeV) electrons at their normal incidence onto a growing single-crystal thin film has been calculated. It is shown that in this case a quantum size effect occurs, which manifests itself in harmonic oscillations of the reflected beam intensity. The oscillation amplitude and period depend on the thickness of the growing film and the energy of the incident electrons. The results obtained are graphically illustrated.