Accepted articles

R.A. Magomedov, E.N. Akhmedov
Institute for Geothermal Research and Renewable Energy of the Joint Institute for High Temperatures of the Russian Academy of Sciences

Abstract: This paper presents a calculation of the state equation isotherms for noble gases: neon, argon, krypton, and xenon in the temperature range from 500 to 3000 K. The calculation was performed using a mathematical model based on a fractal state equation, which has previously demonstrated high efficiency in calculating the P–ρ–T properties of other substances. The obtained results are in good agreement with literature reference data. The dependence of the fitting parameter α of the fractal state equation on density is determined for various temperatures. It is found that for neon, krypton, and xenon, the density dependence is small, but the temperature dependence is noticeable. For argon, the opposite is true: the density dependence is more pronounced, and the temperature dependence is almost absent. To evaluate the effectiveness of the fractal state equation, a comparative analysis of the calculation accuracy is performed and compared to the classical equation of state of a real gas. It is shown that the accuracy of the classical equation decreases with increasing pressure. The fractal equation has high calculation accuracy over the entire studied range of temperatures and pressures.
Keywords: mathematical modeling, fractal equation of state, thermophysical properties of inert gases, neon, argon, krypton, xenon, fractional integro-differentiation, software calculation module

A.A. Misochenko, O.E. Korolkov
Mechanical Engineering Research Institute of RAS

Abstract: The study analyzes the thermal effect of pulsed current during tensile testing in Grade 2 and Grade 4 titanium in coarse‑grained and ultrafine‑grained states. The work demonstrates the determining role of the current duty cycle in the manifestation of electroplastic and thermal effects. It is shown that in the single‑pulse mode (duty cycle 5000-10000), there is a correspondence between the onset of the temperature peak and the yield stress jump. In the multi‑pulse current mode (duty cycle 10), the maximum temperatures increase linearly with increasing current density above 40 A/mm² and can reach approximately 170°C at a current density of 100 A/mm².When the duty cycle is below 5000, thermal effects become the dominant mechanisms. The results of comparing the electroplastic effect manifestation in coarse‑grained and ultrafine‑grained Grade 4 titanium are presented, demonstrating the structural sensitivity of the effect to grain size. A comparison was made of the reduction in the flow stress under the influence of current versus heating by an external source, demonstrating the presence of other contributions to the electroplastic effect beyond the thermal one. Notably, the thermal contribution of the current to the reduction of flow stress in ultrafine‑grained titanium is smaller than in coarse‑grained titanium.
Keywords: electroplastic effect, tension, pulsed current, titanium, thermal effect of pulsed current

E.S. Burlakov¹, D.V. Vishnevetskii¹, E.E. Polyakova¹, D.V. Averkin², A.A. Efimov³, M.Yu. Aleshina^3
1 Tver State University
² All-Russian Scientific Research Institute of Physical-Technical and Radiotechnical Measurements
³ Moscow Institute of Physics and Technology

Abstract: In this work, the effect of silver salts on the self-assembly process in aqueous solutions of L-cysteine methyl ester hydrochloride was studied using UV–visible spectroscopy, dynamic light scattering, electrophoretic light scattering, pH measurements, transmission electron microscopy, and selected-area electron diffraction. The nitrate- and acetate-based systems remained visually stable after storage in the dark for 2 months, whereas the nitrite-based systems began to precipitate after several days. The UV-visible spectra showed no characteristic absorption bands and no pronounced scattering region, indicating the stability and homogeneity of the samples. According to the zeta-potential values, the solutions with L-cysteine methyl ester hydrochloride:silver salt ratios of 1:1,5 and 1:1,75 were the most stable in both systems. The dynamic light scattering results showed that only a small number of nanoparticles formed under conditions of silver ion deficiency, whereas an excess of silver ions produced sufficient scattering intensity for reliable particle-size determination. The pH measurements revealed different trends for the acetate- and nitrate-based systems. transmission electron microscopy and selected-area electron diffraction data showed that the obtained systems form predominantly amorphous, polydisperse, spherical nanoparticles ranging from 5 to 60 nm in size, with some particles reaching approximately 200 nm.
Keywords: L-cysteine methyl ester, silver nitrate, silver nitrite, silver acetate, self-assembly, nanostructured systems

A.M. Rikhmaier, E.M. Chernova, Yu.D. Orlov, M.A. Rikhmaier
Tver State University

Abstract: A systematic analysis of the electron density topology in a number of positional isomers of monochloranthracene is performed. The calculations were carried out using the B3LYP electronic density functional theory with the basis 6-311G. The analysis of the obtained electronic structure was performed using the quantum theory of atoms in the molecule. It has been established that the position of the chlorine atom affects the distribution of electron density in the anthracene core, which is manifested in a change in the values   of atomic charges and volumes, ionization energies, and electron affinity. It has been shown that 9-chloroanthracene is characterized by maximum delocalization of electron density, maximum electron affinity energy and minimum ionization energy, which predicts high mobility of charge carriers and the ability to form rigid crystalline packages. The findings demonstrate that descriptors of electronic topology can serve as an effective tool for predictive design of organic semiconductors at the isolated molecule level.
Keywords: anthracene, monochloranthracene, QTAIM, electron density topology, positional isomerism, molecular electronics, organic semiconductors, ionization energy, electron affinity energy, band gap energy

V.V. Malashenko
Donetsk Institute for Physics and Engineering named after A.A. Galkin

Abstract: Within the framework of the theory of dynamic interaction of defects., the above-barrier motion of edge dislocations in an irradiated metal containing radiation point and nanoscale defects (prismatic dislocation loops) is analyzed. Intense external loads generate high strain rate deformation of irradiated metals. During high strain rate deformation, dislocations accelerate to high velocities, and their kinetic energy exceeds the height of potential barriers generated by structural defects. During above-barrier motion of dislocations, the energy of external loads is converted into the energy of dislocation oscillations. This dissipation mechanism differs significantly from the dissipation mechanism in the low-velocity region. The presence of a gap in the dislocation oscillation spectrum significantly affects the efficiency of this mechanism. This paper considers the case where the gap is generated by the collective interaction of radiation point defects. An analytical expression defining the rate dependence of the dynamic yield strength in irradiated metal is obtained. A new region of dynamic instability of dislocation motion was predicted, caused by a high concentration of prismatic dislocation loops. This dynamic instability is the cause of plastic deformation jumps. Some analytical expressions defining the boundaries of the dynamic instability region are obtained, and numerical estimates of the boundary values are performed.
Keywords: irradiated metals, dislocations, dislocation loops, radiation defects, high-speed deformation

N.A. Teplyakova
Tananaev Institute of Chemistry  Subdivision of the Federal Research Centre «Kola Science Centre of the RAS»

Abstract: Temperature-induced changes in the Raman spectra of the Li_0,015Na_0,985Ta_0,1Nb_0,9O₃ solid solution have been studied in the low-frequency region. This region encompasses the fully symmetric librations of the oxygen octahedra as a whole, vibrations of the Li and Na cations in the cuboctahedral voids, and vibrations of the Nb and Ta cations in the octahedral voids in the temperature range of 22-400°C. As the temperature increases, a significant broadening of the Raman spectrum bands appears. This indicates disordering of the solid solution structure. However, a “softening” (decrease in frequency) of the band in the 50-80 cm^-1 region corresponding to the totally symmetric librations of the oxygen octahedra as a whole is also observed. This fact indicates a misorientation in the structure of the Li_0,015Na_0,985Ta_0,1Nb_0,9O₃ solid solution of oxygen octahedra, while the possibilities for transport of Li ions at high temperatures increase. A predominant broadening (compared to other spectral bands) and a decrease in band intensity have been detected In the 110-160 cm^-1 range. These bands correspond to vibrations of Na⁺ and Li⁺ cations in Li/NaO₁₂ polyhedra. This indicates “melting” of the alkali metal sublattice. Such behavior of the Raman spectrum bands indicates the existence of a phase transition to a state with superionic conductivity in the studied Li_0,015Na_0,985Ta_0,1Nb_0,9O₃ solid solutions.
Keywords: ceramic solid solutions; phase transition; superionic conductivity; Raman scattering

I.A. Surkov¹, L.A. Pasechnik², O.I. Gyrdasova^2
1 Ural Federal University named after the first President of Russia B.N. Yeltsin
² Institute of Solid State Chemistry of the Ural Branch of RAS

Abstract: Solid solutions of the Er₂O₃/ScSZ system were synthesized by a sol-gel method using ethylene glycol as an organic component, which ensures high homogeneity of dopant distribution in the ZrO₂ matrix. Thermolysis of the intermediate sol in air at 700 °C leads to the formation of Zr_0,8Sc_0,2-xEr_xO₂ (x = 0-0,04) compositions based on the tetragonal t–ZrO₂ phase. Ceramic samples with a relative density of 96-98% were obtained at 1500°C. According to X‑ray diffraction data, in the range x = 0-0,01 the sintered ceramics consist of a mixture of cubic (c–ZrO₂) and rhombohedral (r–ZrO₂) phases, whereas at x = 0,02-0,04 a single‑phase cubic structure is formed. Scanning electron microscopy reveals a well‑sintered microstructure with grains closely adhering to each other; pores are closed and have submicron dimensions. The microhardness ranges from 12,3 to 15,6 GPa, which is comparable to that of conventional technical ceramics based on ZrO₂. Co-doping with erbium almost doubles the flexural strength, raising it from 81,2 MPa (undoped ScSZ) to 150,2 MPa for the composition Zr_0,8Sc_0,19Er_0,01O₂. This value exceeds the typical strength of unstabilized ZrO₂ ceramics and demonstrates a pronounced strengthening effect of erbium. The observed strengthening is attributed to the transformation toughening mechanism, as well as to reduced porosity and microstructural optimization achieved through the sol‑gel synthesis. To ensure stability of thermomechanical and thermoelectric characteristics under long‑term and cyclic operating conditions, a co-doping level of 2-3 mol.% Er (x = 0,02-0,03) is preferable, which yields a single‑phase c–ZrO₂ structure that prevents unwanted phase transitions in the working temperature range. Such doping provides the best combination of strength (~154 MPa) and microhardness (~14,5-15,0 GPa), thereby reducing the risk of property degradation. Thus, the developed Er₂O₃/ScSZ materials represent a promising alternative to conventional electrolytes for solid oxide fuel cells, offering high density, mechanical strength, and phase stability.
Keywords: scandium stabilized zirconium oxide, co-doping, erbium oxide, sol-gel synthesis, microhardness, bending strength

G.P. Mikhailov, Yu.G. Voronova
Ufa University of Science and Technology

Abstract: Using quantum-chemical modeling methods, the temperature dependence of the energy gap of the (TiO₂)₁₅ subnanocluster was studied in the range from 10 to 900 K. Within the framework of density functional theory (M06/6-31G(d,p) approximation), it was found that the (TiO₂)₁₅ subnanocluster has a quasi-spherical shape (C_2h symmetry, diameter of 0,9 nm), and its inner core exhibits the atomic order of rutile. Thermostable structures (TiO₂)₁₅ were obtained by the non-empirical molecular dynamics method using the Atom-Centered Density Matrix Propagation scheme. For each temperature, the energy gap E_gap between the lowest vacant and highest occupied molecular orbitals was calculated using the M06/6-31G(d,p) approximation. The obtained data were analyzed using the E_g(T) model dependencies developed for crystalline solids. The qualitative similarity of the temperature dependencies of E_g(T) for the (TiO₂)₁₅ cluster and bulk semiconductors has been established, namely, a non-linear monotonic decrease of the E_g with increasing temperature. As the temperature increases, significant anharmonicity of the (TiO₂)₁₅ cluster vibrations is observed, and the temperature sensitivity of the O 2p (highest occupied molecular orbital) and Ti 3d (lowest unoccupied molecular orbital) molecular orbitals is different, with the titanium orbitals showing a weak dependence. The most adequate and physically interpretable results are obtained using the O’Donnell-Chen model, which takes into account the quantum nature of the subnanocluster vibrations and allows us to determine the average energy of the vibrational modes that determine the temperature dependence of the energy gap.
Keywords: nanocluster, titanium dioxide, density functional theory, energy gap

D.V. Vishnevetskii¹, E.E. Polyakova¹, D.V. Averkin^2
1 Tver State University
² All-Russian Scientific Research Institute of Physical-Technical and Radiotechnical Measurements

Abstract: The effect of the chemical nature of silver salts (silver nitrate, silver nitrite, silver acetate) used as a precursor in the synthesis of cysteine-silver sols on their behavior at different medium acidities was investigated. The visual analysis revealed a similar behavior of all systems: a change in the pH of the medium from an acidic value to an alkaline one in cysteine-silver sols leads to the transition from a homogeneous solution to a turbid one and homogeneous again. Turbidimetric titration and electrophoretic light scattering (zeta-potential measurement) measurements showed that all the systems exhibit an isoelectric point, the value of which depends on the sample preparation history, namely, on the chemical nature of the silver salt. This behavior is associated with the presence of amino and carboxyl groups located on the surface of cysteine-silver sol nanoparticles. Based on previously reported data and the results obtained in this study, a structural model of nanoparticles forming the corresponding sols is proposed.
Keywords: cysteine-silver sol, pH, isoelectric point, turbidity, zeta-potential

D.S. Pavlenko¹, A.L. Bulanova¹, A.V. Pavlenko^2
1 Southern Federal University
² Southern Scientific Center of the RAS

Abstract: In this work, 0,91NaNbO₃–0,09SrZrO₃ (NZNO-0,09) thin films were grown on SrRuO₃/MgO(001) substrates using the high-frequency magnetron sputtering method in an O₂ atmosphere. A comprehensive study of their crystal structure, dielectric response, and polarization characteristics was carried out using X-ray diffraction analysis, dielectric spectroscopy, and measurements of dielectric hysteresis loops. It was established that the obtained films are single-phase, impurity-free, and at room temperature they exist in the antiferroelectric phase. At the same time, in contrast to ceramics of the same composition, they exhibit relaxor behavior in terms of the temperature–frequency dependence of the relative permittivity ε and dielectric loss tangent tg δ. Analysis of the dispersion of ε and tan δ in the temperature range T = 305-460 K and frequency range f = 0,2-500 kHz revealed the presence of contributions from two relaxation processes associated with different polarization mechanisms. A model describing the observed spectra is proposed. The paper discusses the origins of the observed features in the formation of dielectric properties, as well as the high energy efficiency of the NZNO-0,09 films. The obtained results are important for understanding the mechanisms governing the property formation in antiferroelectric nanoscale thin films in view of their application in modern functional electronics.
Keywords: antiferroelectric, dielectric properties, thin films, polarization, high-frequency magnetron sputtering method