卷 70, 编号 1 (2025)

The structure and properties of ZnWO₄ have been simulated using the method of empirical interatomic potentials. The system of consistent interatomic potentials has been developed, which makes it possible to describe the structure, elastic and thermodynamic properties of zinc tungstate and provide the simulation of more complex composite media involving this component.

The copper-containing enzyme thiocyanate dehydrogenase (TcDH) catalyzes oxidation of thiocyanate to cyanate and elemental sulfur. To date, the spatial structures of two bacterial TcDHs (tpTcDH and pmTcDH) are known. Both enzymes are dimers and contain a trinuclear copper center in the active site. The important difference between these enzymes is that in a crystal, the subunits of the tpTcDH dimer are in identical conformations, while the subunits of the pmTcDH dimer are in different conformations: closed and open. To clarify the role of copper ions in changing the TcDH conformation, the structure of the apo-form of pmTcDH was established, in which both subunits of the dimer had the closed conformation. Soaking of apo-form crystals with copper led to the restoring of the trinuclear center and the conformational rearrangements of the subunits.

We experimentally demonstrated (using micro-Raman spectroscopy and transmission electron microscopy) and through numerical modeling that when an intense (10¹³−10¹⁴ W/cm²) femtosecond (~100 fs) laser pulse impacts the surface of silicon with (111) orientation, new polymorphic phases Si-III and Si-XII are formed on the surface and in the volume, localized in lattice defects as well as at the periphery of the ablation crater. This localization of phases is caused by the multi-stage nature of laser-induced phase transitions in silicon, specifically, the phase transitions are initiated by a shock wave, resulting in a cascading transformation process on sub-nanosecond timescales: Si-I => Si-II => => Si-III/Si-XII. The phase transition Si-I => Si-II occurs at the front of the shock wave, while at the rear of the shock wave, a field of dynamic stresses arises in the material, allowing the phase transition Si-II => Si-III/Si-XII to occur. On sub-microsecond timescales, most of the new phases disappear as the material relaxes back to its original state.

The luminescent and laser properties of ZnO microtubes synthesized by a modified thermal evaporation method were studied using photoluminescence spectroscopy. It was shown that whispering gallery modes are responsible for lasing in the near UV range. The possibility of achieving low lasing thresholds (down to ~ 8 kW/cm²) and high optical quality factors (over 3900) was demonstrated. A mechanism for the formation of such microcrystals was proposed, based on the assumption of simultaneous growth and etching along the [0001] crystallographic direction.

A theoretical and experimental study of the effect of imperfections of the polarizer, analyzer and photomultiplier tube (PMT) on the measurement results of the transmission coefficient spectra of the langasite family crystals cut parallel to the optical axis has been carried out. It is shown that in the absence of an analyzer, oscillations appear on the transmission spectra, the amplitude of which depends on the rotation of the crystal. These oscillations are associated with linear birefringence and appear due to the imperfection of the PMT, which plays the role of a partial analyzer. From the obtained spectra, the parameters of the PMT are calculated depending on the wavelength. The calculation of the birefringence of the studied crystals was carried out and an estimate of the error of such calculation was obtained. It is shown that the imperfection of optical elements does not lead to additional errors in the calculation of birefringence. Thus, when the plate is cut perpendicular to the optical axis, circular birefringence is manifested, when parallel, there is linear birefringence.

The features of ion transfer in α-TeO₂ paratellurite crystals under conditions of an external constant electric field have been studied by the method of molecular dynamics. It is shown that the anisotropy of ion transport is more pronounced when the E field is applied along the c axis: at E = 350 kV/mm, diffusion increases by about 2 times for crystals with oxygen vacancies and 3 times for samples with additional interstitial oxygen atoms.

Superprotonic crystals Cs₃(HSO₄)₂(H₂PO₄) and Cs₄(HSO₄)₃(H₂PO₄) have been investigated by conducting atomic force microscopy at increasing temperature. Local volt-ampere characteristics have been measured and an increase in conductivity at 413–453 K for Cs₃(HSO₄)₂(H₂PO₄) and Cs₄(HSO₄)₃(H₂PO₄) by two and three orders of magnitude, respectively, has been recorded. Differences in the conductive characteristics of crystals of different compositions in the vicinity of the phase transition are shown. Information on topographic and electrical features of crystalline phases before and after exposure to temperature and electric fields has been obtained. The influence of external factors on the stability of the surface microstructure is evaluated. Possible mechanisms of structural-phase transformations of isostructural compounds with different ratio of sulfate and phosphate groups are discussed.

The reflection coefficient of medium-energy electrons (about 10 KeV) was calculated for their normal incidence on a thin growing single-crystal film. It is shown that in this case a quantum size effect occurs, which manifests itself in harmonic oscillations of the intensity of the reflected beam. The amplitude and period of oscillations depend on the thickness of the growing film and the energy of the incident electrons. A graphic illustration of the results obtained is provided.

Electrically conductive micro- and nanofibrous nonwoven materials were obtained by electrospinning of solutions of polyaniline and a number commodity polymers (polyamide-6, polylactic acid, polystyrene, polyethylene oxide). The average fiber diameter is in the range of 0.5–6 μm, while the addition of polyaniline into the spinning solution leads to a decrease in fiber diameter. The composition of the obtained materials was confirmed by IR spectroscopy. It was found that during the electrospinning process the supramolecular structure of polyamide-6 and polylactide changes (from α-phase to γ- and amorphous phases, respectively), and polyaniline does not form crystalline structures. The specific electrical conductivity of the obtained nonwoven fabrics can reach 10⁻³ S/cm, which allows their application both in tissue engineering and in organic electronics.

The method of molecular dynamics has been used to simulate heteronanostructures formed when silver iodide and silicon oxide nanoparticles are filling single-walled carbon nanotubes of the “armchair” type (12,12). The results of computer modeling show that stable nanostructured “internal nanocomposites” with AgI inclusions and silicon oxide clusters of various configurations can be formed in such tubes. Si₃O₆ clusters of linear and planar types have varying degrees of influence on the mobility of silver ions in the studied complex heteronanostructures of AgI|Si₃O₆@SWCNT.

The crystal structure of {In_0.1Ga_0.9As/GaAs} × 10 and {In_0.2Ga_0.8As/GaAs} × 10 epitaxial multilayer films on GaAs substrates with different orientations has been studied (100), (110), (111)A in order to identify features that may be related to the previously discovered increased efficiency of terahertz radiation generation in films with orientations (110) and (111)A. Significant concentrations of twins and package defects were found in films on non-standard GaAs (110) and (111)A substrates. The composition and thicknesses of individual layers of heterostructures on GaAs (100) substrates have been refined by analyzing thickness fluctuations on diffraction reflection curves.

The basic composition of polychrome enamels of three bronze items found on the territory of Vladimir and Suzdal Opolje dating from the 12^th and 13^th centuries (a temporal pendant, a pendant icon and a cross) was studied by atomic emission spectroscopy and energy dispersive X-ray microanalysis. The items have rich coloration, which allowed us to study the technological features of a wide range of colored enamels: white, black, gray, light gray, deep-blue, red-brown, brown, green, blue-green, turquoise, yellow. The obtained results suggested the Byzantine origin of the enamels and the local production of the items themselves. The work was carried out within the state assignment of the National Research Centre “Kurchatov Institute” using the equipment of the Shared Research Center “Structure diagnostics of materials” in the part of XRF studies.

An additive model has been developed for calculating the combinatorial (Shannon-like) complexity of a signature of the 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 tilings of a zeolite type. Correlations of the calculated complexity of a signature of the tiling and the combinatorial complexity of the tiling-generating structure were found.