PhC-2022

E.V. Maraeva¹, S. Tokmeilova¹, D.R. Sagitova¹, I.E. Kononova¹, V.A. Moshnikov¹, S.A. Skornikova^2
1 Saint Petersburg Electrotechnical University «LETI»
² Irkutsk National Research Technical University

Abstract: The paper considers a series of zeolite materials used as catalysts. Since the formation of mesoporosity in a microporous matrix is one of the methods for increasing the efficiency of zeolite materials in catalysis, it is necessary to control their porous structure parameters. The effect of post-synthetic treatment with acid and alkali solutions on the specific surface area of zeolites of the BEA type has been studied. The method of low-temperature (at 77 K) adsorption of nitrogen vapors was used to determine the external specific surface area (excluding micropores) and the volume of micropores in the samples on a Sorbi device. It has been shown that modification of BEA-type zeolite with concentrated mineral acids leads to both a decrease in the volume of micropores and a decrease in the specific surface area. At the same time, it was established by the X-ray phase analysis that the treatment with concentrated acids does not lead to destruction of the crystal structure of zeolites. In the case of treatment with alkali solutions, the specific surface area of the samples increases and the volume of micropores sharply decreases.
Keywords: zeolites, BEA type, hierarchy, mesopores, micropores, adsorption, specific surface area

N.I. Nepsha, A.D. Veselov, K.G. Savina, S.S. Bogdanov, A.Yu.. Kolosov, V.S. Myasnichenko, N.Yu.. Sdobnyakov
Tver State University

Abstract: In this work, bimetallic Cu-Ag nanoparticles of five stoichiometric compositions of various sizes were studied by molecular dynamics method using a many body EAM potential. Regularities of the structure formation are established, their characteristic features are described. In particular, in compositions with 10, 70, and 90 at.% Cu content, after the melt cooling, typical fcc structures with intersecting atomic planes of the hcp phase are formed. In compositions of 30 and 50 at.% Cu, the fraction of identified phases does not exceed 20% of the total number of atoms. A tendency to the formation of a core-shell structure was revealed in the case of a high copper content, while in the case of a high silver content, a so-called onion structure is formed. Using the caloric curves of the potential term of the internal energy, the melting and crystallization temperatures were determined. It has been established that the concentration dependences of the melting temperature of bimetallic Cu-Ag nanoparticles have a minimum corresponding to the equiatomic composition for all sizes. For the crystallization temperature, both the concentration dependences and the size dependences are less pronounced, but the minimum value of the crystallization temperature also corresponds to the equiatomic composition for all sizes; with an increase in the size of bimetallic Cu-Ag nanoparticles, a slight increase in the crystallization temperature is observed.
Keywords: molecular dynamics method, LAMMPS, EAM potential, polyhedral template matching method, bimetallic nanoparticles, silver, copper, structure formation, melting and crystallization temperatures

N.V. Sidorov, M.V. Smirnov, R.A. Titov, N.A. Teplyakova, M.N. Palatnikov
Tananaev Institute of Chemistry  Subdivision of the Federal Research Centre «Kola Science Centre of the Russian Academy of Sciences»

Abstract: The optical properties of nominally pure LiNbO_3stoich, near-stoichiometric LiNbO_3stoich (6,0 wt% K₂O), LiNbO_3cong and LiNbO₃:B (0,55 and 0,83 mol% B₂O₃ in the charge) crystals in the visible region of the spectrum (λ = 380-700 nm) were studied by photoluminescence. LiNbO₃:B crystals were grown by Czochralski using the technology of a direct solid-phase doping of the congruent charge by boron oxide (B₂O₃). The photoluminescence intensity increases in the series of crystals: LiNbO_3stoich, LiNbO_3stoich (6,0 wt% K₂O), and LiNbO_3cong. The photoluminescence intensity is determined by the concentration of deep electron traps (NbLi – «niobium antisite») and the stoichiometry of these crystals. The photoluminescence intensity of LiNbO₃:B (0,55 and 0,83 mol% B₂O₃ in the charge) crystals is close to the photoluminescence intensity of LiNbO_3stoich crystal. This can be explained by the fact that the composition and structure of LiNbO₃:B (0,55 and 0,83 mol% B₂O₃ in the charge) crystals approach the composition and structure of the stoichiometric crystal.
Keywords: lithium niobate, crystal, defects, direct solid-phase doping, photoluminescence

N.V. Sidorov, A.V. Kadetova, R.A. Titov, N.A. Teplyakova, M.N. Palatnikov
Tananaev Institute of Chemistry  Subdivision of the Federal Research Centre «Kola Science Centre of the Russian Academy of Sciences»

Abstract: Specific features of the defect structure of nominally pure LiNbO₃:B crystals were studied by the X-ray diffraction analysis. Nominally pure LiNbO₃:B crystals were grown by Czochralski using the technology of the direct solid-phase doping of the congruent charge by orthoboric acid (H₃BO₃). The bonds lengths of Me-O in MeO₆ clusters (Me-Li, Nb) determine the ferroelectric and nonlinear optical properties of the lithium niobate crystal. The values of these bonds in LiNbO₃:B crystals differ significantly from the bonds lengths of the nominally pure congruent crystal LiNbO_3cong. The differences in the bonds lengths are caused by a change in the properties of the boron-containing melt, technological parameters of the growth of LiNbO₃:B crystals, and the localization of a trace amounts of boron in tetrahedral voids of the lithium niobate crystal structure. The results of the study of LiNbO₃:B crystals were compared with those for nominally pure LiNbO_3cong crystals and near-stoichiometric LiNbO_3stoich (5,5 wt% K₂O) ones.
Keywords: lithium niobate, crystal, defects, direct solid-phase doping, X-ray diffraction analysis

R.A. Magomedov, E.N. Akhmedov
The Joint Institute for High Temperatures of the Russian Academy of Sciences

Abstract: The paper presents the calculation of isotherms of the equation of state of water vapor in the temperature range from T = 773 K to T = 1673 K. The calculation was made using a specially developed software module “Fract EOS”. An approach that improves the accuracy of calculations of the previously described method is proposed. If there are tabular data of the P-V-T (P-ρ-T) ratio for several temperatures and the pressure dependences of the fractional derivative exponent α(ρ) (which is fitting parameter for the proposed model) obtained from them, then it is possible to obtain the dependence α(ρ) for any temperature within the range. After that, the equation of state can be calculated at a given temperature with high accuracy, without fitting α by experimental values. The results obtained are in good agreement with experimental data. It is shown that proposed method is suitable for calculating isotherms in the temperature ranges not presented in tabulated reference data.
Keywords: equation of state, integral-differentiation of fractional order, Maxwell relations, Helmholtz potential, partition function, water vapor, isotherm, thermophysical properties

A.S. Strechen, Yu..A. Kurnosov, A.Yu.. Karpenkov, A.I. Ivanova, A.I. Sinkevich, E.M. Semenova, Yu..G. Pastushenkov
Tver State University

Abstract: The results of the study of the crystal structure, magnetic properties, as well as of micro-and domain structure of the surface of a series of compounds Tb_0,16Ho_0,84Fe_2,00-xCo_x (x = 0,1; 0,2; 0,3; 0,4) are presented. It is shown that an increase in the relative content of cobalt leads to a decrease in the crystal lattice parameter a from 7,310 Å at x = 0,1 to 7,304Å at x = 0,4. At the same time, the Curie temperature increases accordingly from 581 to 614 K. It has been experimentally established that, as x increases, the specific saturation magnetization decreases linearly with increasing temperature. It has been found that the mechanical impact on the surface of sections during polishing can lead to the appearance of a regular microrelief. The results of studying the domain structure of the surface are presented. It is shown that the configuration and linear dimensions of the domains change as a result of the impact on the surface of the samples.
Keywords: intermetallics, Laves phase, magnetic properties, surface, microstructure, domain structure

S.A. Elcheparova, A.A. Kokoevа
Kabardino-Balkarian State University named after H.M. Berbekov

Abstract: It was of interest to search for luminescent reactions to terbium in complexes with sulfosalicylic acid derivatives and to enhance them by studying the effect of third components (aminopolycarboxylic acids, organic bases and surfactants). As the results of the conducted studies have shown, surfactants increase the intensity of the glow of terbium ions in complexes with sulfosalicylic acid derivatives. The existence of a bright luminescent reaction of green terbium in complex with the methyl ester of S-(4-bromanilide) sulfosalicylic acid has been established. Optimal conditions for the complexation of terbium have been selected and highly sensitive luminescent methods for the determination of terbium in various objects have been developed. Terbium is converted into a luminescent complex compound with an organic reagent –
methyl ether S-(4-bromanilide) sulfosalicylic acid in the presence of a cationic surfactant decylpyridinium chloride in a ratio of 1: 2: 13, pH = 7,9 ± 0,08. The resulting complex compound of terbium, when irradiated with ultraviolet light from a mercury lamp, gives intense green luminescence, stable during standing and irradiation. The proposed method makes it possible to determine terbium in oxides of rare earth elements, which are luminescence quenchers with a sensitivity of 10-6 – 10-8%, bypassing the extraction stage.
Keywords: nanoscale particles, rare earth elements, lanthanides, organic reagent, complex compound, terbium, luminescence, detection limit

V.A. Anofriev¹, A.V. Nizenko¹, D.V. Ivanov¹, A.S. Antonov², N.Yu.. Sdobnyakov^1
1 Tver State University
² Tver State University, Docent, Tver State Agricultural Academy

Abstract: In this paper, using various software products (Gwyddion, Mountains 9 DigitalSurf, Image Analysis P9) as well as our own program FractalSurface, we analyzed the possibilities of calculating the fractal dimension for various types of data using several numerical methods (cube counting method, triangulation method, variation method, as well as methods of the spectrum power, «scaling» analysis, morphological envelopes) and the possibilities for their working with the obtained values, such as: selecting a linear section of the graph for recalculating the final value of dimension, using matrix convolutional filters with different convolution kernels for image processing and of the batch analysis of the studied images. At the current time, there is no software product that would satisfy all the requirements for image analysis for the presence of self-affine structures, however, the availability of sufficient functionality mainly depends on the type of study. The comparative analysis of the obtained results allows us to evaluate the capabilities of the software product for further use as tools for automating the process of determining the fractal dimension and of the primary image processing.
Keywords: fractal dimension, cube counting method, triangulation method, variance method, power spectrum method, scaling analysis method, morphological envelopes method, image processing software

Z.A. Akhmatov¹, Z.A. Akhmatov^2,1
1 Kabardino-Balkarian State University named after H.M. Berbekov
² Southern Mathematical Institute of the Vladikavkaz Scientific Center of the RAS

Abstract: Using first principles calculations, the possibility of controlling the electronic band structure of the single-layer graphene was investigated. It is shown that when potassium atoms are adsorbed on the graphene surface, an energy gap appears in its electronic spectrum. It was also observed that the band gap strongly depends on the number of adsorbed atoms, namely, with an increase in the number of adsorbed atoms, the band gap in graphene can either increase or disappear. For example, when there is one potassium atom per 32 carbon atoms in the graphene lattice, the band gap is ΔE = 0,1 eV. An increase in the number of potassium atoms to two leads to disappearance of the energy gap, while for three potassium atoms ΔE = 0,22 eV. It should also be noted that the appearance of a band gap during adsorption does not break the symmetry of the graphene sublattices. This observation seems interesting to us, since according to many authors, it is the break of the sublattices symmetry that is the main reason for the appearance of a band gap in graphene.
Keywords: graphene, electronic band structure, ab initio calculations, adsorption, alkali metal atoms

I.N. Belyaeva¹, I.K. Kirichenko², N.N. Chekanova^3,4
1 Belgorod National Research University
² Kharkiv National Automobile and Highway University
³ Kharkiv National University named after V. N. Karazin
⁴ Department of Information Technology and Mathematic Modeling, Karazin Business Schoo

Abstract: In the current scientific literature, a variety of nonlinear ordinary differential equations are widely and successfully used to describe real processes in various fields of natural sciences: optics, elasticity theory, molecular physics, etc. For example, the Ermakov and Riccati equations are used to solve the quantum Schrodinger equation, in electrodynamics. However, unfortunately, there are no well-and reliably developed and generally accepted methods for solving nonlinear differential equations. In addition, most of the Riccati equations are not integrated even in quadratures. In this paper, to construct solutions to the nonlinear Ermakov and Riccati equations, it is proposed to use the corresponding so-called connected linear differential equations, the solutions of the latter are in the form of power series using modern computer systems of analytical calculations.In this paper, solutions for some nonlinear Ermakov and Riccati equations are calculated using this proposed method. It is shown by direct substitution that the obtained solutions in the form of power series satisfy the considered nonlinear equations of Ermakov and Riccati with a known accuracy. Solutions of nonlinear Ermakov and Riccati equations can be used to describe the chemical and physical properties of nanostructures at the quantum level. Besides, solutions of nonlinear Ermakov and Riccati equations can be successfully applied in solving stationary and time-dependent Schrodinger equations.
Keywords: ordinary differential equations, Ermakov equation, Riccati equation, mathematical modeling, power series, Maple computer system