East European Journal of Physics

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ISSN : 23124334
Current Publisher: V. N. Karazin Kharkiv National University (10.26565)
Total articles ≅ 147
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East European Journal of Physics; doi:10.26565/2312-4334

Elena V. Romashchenko, Aleksander A. Bizyukov, Igor O. Girka
East European Journal of Physics pp 60-65; doi:10.26565/2312-4334-2020-1-04

Generation of metal plasma in vacuum arc discharge is always accompanied by a production of macroparticles (MPs). The MP contamination in coatings is the most important technological problem in plasma immersion ion implantation (PIII). For the case of PIII with long pulse duration, the results of theoretical study of MP charging and dynamics in the plasma sheath are presented. To describe the MP charging in the sheath the sheath model is combined with orbital motion limited (OML) theory. The MP charging in the sheath is studied with taking into account emission processes from MP surface as well as kinetic electron emission (KEE) from the high voltage substrate. The charge and dynamics of MP are governed by local parameters of counter fluxes of ions and secondary electrons from the substrate. The MP charge depends on the MP local position within the sheath. The dominant role in MP charging is shown to be played by KEE from the substrate, which is an important feature of PIII. KEE from the substrate changes the potential profile within the sheath, the sheath thickness, and current balance on MP surface. MP charge is obtained to be negative because it is caused by higher current density of secondary electrons from the substrate than that of ions. The latter is possible for KEE yield larger than a unit. The substrate biasing influences both the release of secondary electrons from the substrate under ion impact and their acceleration in the sheath. The increasing of negative substrate bias is demonstrated to result in the increasing of absolute value of negative MP charge, and, thereby, the increasing of electrostatic reflection of MP from the substrate. The negative substrate biasing is shown to be the effective alternative method to reduce MP contaminations in coatings without applying any magnetic filters.
Michael I. Kopp, Anatoly V. Tur, Konstantin N. Kulik, Volodymyr V. Yanovsky
East European Journal of Physics pp 5-36; doi:10.26565/2312-4334-2020-1-01

In this paper, we investigated a new large-scale instability that arises in an obliquely rotating convective electrically conducting fluid in an external uniform magnetic field with a small-scale external force with zero helicity. This force excites small-scale velocity oscillations with a small Reynolds number. Using the method of multiscale asymptotic expansions, we obtain the nonlinear equations for vortex and magnetic disturbances in the third order of the Reynolds number. It is shown that the combined effects of the Coriolis force and the small external forces in a rotating conducting fluid possible large-scale instability. The linear stage of the magneto-vortex dynamo arising as a result of instabilities of -effect type is investigated. The mechanism of amplification of large-scale vortex disturbances due to the development of the hydrodynamic - effect taking into account the temperature stratification of the medium is studied. It was shown that a «weak» external magnetic field contributes to the generation of large-scale vortex and magnetic perturbations, while a «strong» external magnetic field suppresses the generation of magnetic-vortex perturbations. Numerical methods have been used to find stationary solutions of the equations of a nonlinear magneto-vortex dynamo in the form of localized chaotic structures in two cases when there is no external uniform magnetic field and when it is present.
Sukhender, Lalit Mohan, Sudesh Kumar, Deepak Sharma, Ajay Singh` Verma
East European Journal of Physics pp 69-80; doi:10.26565/2312-4334-2020-2-05

In this paper, we have studied the structural, electronic, optical and magnetic properties of Co2CrZ (Z= Al, Bi, Ge, Si) compounds by using two different methods one is full potential linearized augmented plane wave (FP-LAPW) method as implemented in WIEN2k and second is pseudo potential method as implemented in Atomistic Tool Kit-Virtual NanoLab (ATK-VNL). The respective band gaps in their minority-spin of Co2CrZ (Z= Al, Bi, Ge, Si) are 0.696, 0.257, 0.602 and 0.858 eV near the Fermi level, which is implemented in WIEN2k code and showing 100% spin polarization. Further, these compounds have been found to be perfectly half-metallic ferromagnetic (HMF). However, above mentioned compounds shows zero band gaps in ATK-VNL code. The calculated magnetic moment of these compounds Co2CrZ (Z= Al, Bi, Ge, Si) are 3.06, 4.99, 3.99 and 3.99µB respectively in FP-LAPW method. However, the respective magnetic moment of these compounds is found to be 3.14, 5.08, 4.11 and 4.08µB in ATK-VNL code. Optical properties play an important role to understand the nature of material whether it can be used as optoelectronics device. From the optical Spectra, complex dielectric functions calculated values are 312.370 and 141.991, 299.812 and 111.368, 288.127 and 106.342, 290.688 and 99.095 for the compounds Co2CrZ (Z= Al, Bi, Ge, Si) respectively by using WIEN2k. The maximum energy loss is observed between 11.4 to 13eV for above these compounds. The refractive index values for the compounds Co2CrZ (Z= Al, Bi, Ge, Si) are observed as 18.104, 17.602, 17.252 and 17.289 respectively. In the optical conductivity spectrum a sharp peak is observed at 1.6 - 2.3eV. В этой работе мы изучили структурные, электронные, оптические и магнитные свойства соединений Co2CrZ (Z = Al, Bi, Ge, Si) с помощью двух различных методов, один - это метод полноценной линеаризованной расширенной плоской волны (FP-LAPW) реализован в WIEN2k, а второй - псевдопотенцийний метод, реализованный в Atomistic Tool Kit-Virtual NanoLab (ATK-VNL). Соответствующие запретные зоны для Co2CrZ (Z = Al, Bi, Ge, Si) находятся около уровня Ферми 0,696, 0,257, 0,602 и 0,858 эВ, что реализовано в коде WIEN2k и показывают 100% спиновую поляризацию. Кроме того, было обнаружено, что эти соединения являются идеально напивметаличнимы ферромагниты (HMF). Однако вышеупомянутые соединения показывают нулевые запретные зоны в коде ATK-VNL. Исчисленный методом FP-LAPW магнитный момент этих соединений Co2CrZ (Z = Al, Bi, Ge, Si) составляет 3,06, 4,99, 3,99 и 3,99 µB соответственно. Однако в коде ATK-VNL соответствующий магнитный момент этих соединений составляет 3,14, 5,08, 4,11 и 4,08 µB. Оптические свойства играют важную роль для понимания природы материала, можно ли его использовать как устройство оптоэлектроники. Вычисленные из оптических спектров комплексные диэлектрические функции с использованием WIEN2k составляют 312,70 и 141,991, 299,812 и 111,368, 288,127 и 106,342, 290,688 и 99,095 для соединений Co2CrZ (Z = Al, Bi, Ge, Si) соответственно. Максимальные потери энергии для вышеуказанных соединений наблюдаются между 11,4 до 13эВ. Значение показателя преломления для соединений Co2CrZ (Z = Al, Bi, Ge, Si) наблюдаются как 18.104, 17.602, 17.252 и 17.289 соответственно. В спектре оптической проводимости резкий пик наблюдается при 1,6-2,3эВ. У цій роботі ми вивчили структурні, електронні, оптичні та магнітні властивості сполук Co2CrZ (Z = Al, Bi, Ge, Si) за допомогою двох різних методів, один – це метод повноцінної лінеаризованої розширеної плоскої хвилі (FP-LAPW) реалізований у WIEN2k, а другий – псевдопотенційний метод, реалізований у Atomistic Tool Kit-Virtual NanoLab (ATK-VNL). Відповідні заборонені зони для Co2CrZ (Z = Al, Bi, Ge, Si) знаходяться біля рівня Фермі 0,696, 0,257, 0,602 і 0,858 еВ, що реалізовано в коді WIEN2k і показують 100% спінову поляризацію. Крім того, було виявлено, що ці сполуки є ідеально напівметалічними феромагнітами (HMF). Однак вищезгадані сполуки показують нульові заборонені зони в коді ATK-VNL. Обчислений методом FP-LAPW магнітний момент цих сполук Co2CrZ (Z = Al, Bi, Ge, Si) становить 3,06, 4,99, 3,99 і 3,99 µB відповідно. Однак у коді ATK-VNL відповідний магнітний момент цих сполук становить 3,14, 5,08, 4,11 та 4,08 µB. Оптичні властивості відіграють важливу роль для розуміння природи...
Abdullah Al Zaman, M.R. Islam, H.M.A.R. Maruf
East European Journal of Physics pp 111-120; doi:10.26565/2312-4334-2020-1-10

Superconducting Magnetic Energy Storage (SMES) is an exceedingly promising energy storage device for its cycle efficiency and fast response. Though the ubiquitous utilization of SMES device is restricted because of the immense cost of cryogenic refrigeration system to sustain the superconducting state but with the continuous evolution of high Tc superconductors, SMES is turning into a major contender to the existing energy storage devices in the future. Among its several parts, the superconducting coil is considered to be the most crucial segment of this technology and the inductance generated in the coil determines the quantity of stored energy. In this paper, the possible geometrical configurations of SMES coil have been demonstrated. High Tc superconducting tapes are usually employed to form these configurations worldwide. BSCCO (Bismuth strontium calcium copper oxide)-2223 tape superconductor has been considered for studying the conceptual designs of superconducting coil of SMES. Before estimating the results, the value of critical current at different magnetic field densities and temperatures have been addressed through the study of superconducting tape characterization. Numerical results and the relationship among the several parameters for both the solenoid and toroid configurations in different specifications have been presented. Based on the results, the size ratio in solenoid and the mean toroid diameter in toroid arrangement is found to play the vigorous roles in the generation of inductance and hence the energy storage. The results also match the propensity of other studies. Suggestions for maximum energy gain from a specific solenoid configuration have been provided. Future research scopes with alternative superconducting tapes and limitations of this study have been briefly conferred.
Dmytro V. Kutnii, Dmytro D. Burdeynyi, Stanislav A. Vanzha, Natalia V. Rud
East European Journal of Physics pp 104-110; doi:10.26565/2312-4334-2020-2-09

Influence of mass bias effect, isobaric and polyatomic interferences on the results of 234U/238U, 235U/238U, 236U/238U isotope ratio determination in uranium oxide by sector-field ICP-MS was studied. Uranium isotopic standards CRM U100, CRM U200 based on triuranium octoxide (U3O8) and single-collector mass spectrometer ICP-SFMS ELEMENT 2 were used for research. It has been demonstrated that the mass bias effect has most influence on the results of uranium isotope ratios determination. To investigate the influence of the mass bias effect on the determinations of uranium isotope ratios, the external standardization calibration was used with three models (linear, power, exponential) describing the behavior of the specific discrimination coefficient β versus the mass of measured isotopes. The mass discrimination factor has been found to vary from 6.00 ´ 10-3 to 1.20 ´ 10-2. The advantage for using the (power/exponential)-law models of the β=F(Δm) relationship for correcting measured isotope ratios was justified. In case of polyatomic interferences, the efficiency of uranium hydride ion (235U1H+) formation is 3.54 ´ 10-5, while the impact of isobaric overlapping due to the contribution of scattered 238U ions to the intensities of less abundant 236U and 235U ions reaches 8.17 ´ 10-6. The relative measurement error for the 234U/238U, 236U/238U , ratios was found to be < 0.5 %, and for the 235U/238U, ratio less than 0.1 %. The calculated standard uncertainty u of the 234U/238U, 235U/238U, 236U/238U isotope ratio measurements in the CRM U100 was 0.563, 0.322 and 0.856 %, respectively. These are reasonable estimates in comparison with the uncertainties of certified values of 0.296, 0.097 and 0.265 %. Исследовано влияние эффектов дискриминация ионов по массам, изобарных и полиатомных интерференций на результаты измерений изотопных отношений , , в оксиде урана методом масс-спектрометрии с двойной фокусировкой. Для проведения исследований использовали сертифицированные изотопные стандарты на основе октаоксида триурана () CRM U100, CRM U200 и одноколлекторный масс-спектрометр ICP-SFMS ELEMENT 2. Показано, что основным эффектом, влияющим на результаты определения изотопных отношений урана, является дискриминация ионов по массам. Для изучения влияния эффекта дискриминации ионов по массам на результаты определения изотопных отношений урана, применяли способ внешнего стандарта с тремя моделями (линейной, степенной и экспоненциальной) зависимости удельного коэффициента дискриминации от масс измеряемых изотопов. Рассчитан коэффициент степени дискриминации для линейной, степенной и экспоненциальной моделей зависимости удельного коэффициента дискриминации от масс измеряемых изотопов, который варьируется от 6,00 ´ 10-3 до 1,20 ´ 10-2. Обосновано преимущество использование степенной либо экспоненциальной моделей зависимости для корректирования измеряемых изотопных отношений. При возникновении полиатомных интерференций эффективность образования ионов гидрида урана () составляет 3,54 ´ 10-5, а величина эффекта изобарных наложений вследствие вклада рассеянных ионов в интенсивности менее распространенных и – 8,17 ´ 10-6. Проанализированы метрологические характеристики аналитических результатов, в частности, относительная погрешность измерений изотопных отношений , составила < 0,5 %, а для отношения – менее 0,1 %. Рассчитанная стандартная неопределенность измерений изотопных отношений , , в стандарте CRM U100 составила 0,563; 0,322 и 0,856 % соответственно, что выглядит удовлетворительно по сравнению с величинами неопределенности сертифицированных значений: 0,296; 0,097 и 0,265 %. Досліджено вплив ефектів дискримінація іонів по масах, ізобарних і поліатомних інтерференцій на результати вимірювань ізотопних співвідношень , , в оксиді урану методом мас-спектрометрії з подвійним фокусуванням. Для проведення досліджень використовували сертифіковані ізотопні стандарти на основі октаоксіда тріурана () CRM U100, CRM U200 і одноколлекторний мас-спектрометр ICP-SFMS ELEMENT 2. Показано, що основним ефектом, що впливає на результати визначення ізотопних...
Artem S. Naumovets, Yurii M. Poluektov, Valery D. Khodusov
East European Journal of Physics pp 124-135; doi:10.26565/2312-4334-2020-2-12

Thermodynamic properties of diamond are theoretically investigated on the ground of self-consistent description of a phonon gas in lattice, which generalizes the Debye model with taking into account the phonon-phonon interaction. In many cases properties of crystals of certain symmetry can be well approximated by a model of an isotropic continuous medium, if its elastic moduli are chosen optimally. They should be found for a crystal of each symmetry from the condition of their proximity to the exact elastic moduli, which are measured experimentally and are given in the corresponding tables. At high temperatures, the nonlinear phonon interaction takes into account both three- and four-phonon interactions. In this reason we take into account not only the second-order elastic moduli tensor in the reduced isotropic crystal model, but also the third- and fourth-order elastic moduli tensors, which are all together characterized by nine independent components. Account of the phonon-phonon interaction leads to the redefinition of the phonon’s speed and of the Debye energy. Their dependence on the temperature occurs. In the absence of interaction and neglecting the nonlinear effects, the phonons are the same as that of the Debye model. They are called "bare" or "Debye". Phonons whose speed is renormalized due to the interaction are called the “self-consistent” ones. It is shown that, at high temperatures, the theory predicts the linear in the temperature deviation of the isochoric heat capacity from the Dulong-Petit law. Unlike for the most crystals, where the decrease in the isochoric heat capacity is observed, our calculations for diamond and crystals with diamond structure predict the linear increase of the isochoric heat capacity with the temperature, viewed experimentally. The isobaric heat capacity of diamond, similar to other substances, linearly increases with the temperature.
Sraja Chauhan, Ajay Singh Verma
East European Journal of Physics pp 136-139; doi:10.26565/2312-4334-2020-2-13

In this paper, we have investigated the charge stability diagram and conductance dependence on source drain bias and gate voltage of carbon nanotube based single electron transistor (SET) by using first principle calculations. All calculations have been executed by using ATK-VNL simulation package based on density functional theory (DFT). We have applied these calculations for carbon nanotube based SET; the nanotube has been placed just above the dielectric ( ) in between the source and drain electrodes of gold. The single walled carbon nanotube has been used in SET, which have ultra-small diameter and (4,0) configuration. The addition energy of the device has been calculated, which can be defined as the difference between the electron affinity, and ionization energies. The calculated values of energies have been found to be -10.17694 eV and -11.04034 eV for isolated phase and SET environment respectively. In electrostatic environment, the results were showing the regularization of molecular energy levels and therefore the addition energy reduced. The calculations for additional energies, variations of total energies to that of the gate voltages and charge stability diagram (CSD) have also been done in this study.
East European Journal of Physics; doi:10.26565/2312-4334-2020-2

Valeriya M. Trusova, Kateryna Vus, Olga Zhytniakivska, Uliana Tarabara, Hiroyuki Saito, Galyna Gorbenko
East European Journal of Physics pp 118-123; doi:10.26565/2312-4334-2020-2-11

Amyloid fibrils represent a special type of protein aggregates that are currently receiving enormous attention due to their strong implication in molecular etiology of a wide range of human disorders. Amyloid fibrils represent highly ordered self-assemblies sharing a core cross-β-sheet structure. Such organization of the fibrils is responsible for amyloid insolubility and exceptional mechanical properties. The remarkable rigidity of the protein fibrillar aggregates is due to intra- and interstrand hydrogen bonds which stabilize the β-strand scaffold of amyloid fibrils. Increasing evidence indicates that physical properties of amyloid assemblies, especially their mechanical characteristics, play essential role in determining their cytotoxic action. This highlights the necessity of deciphering the correlation between the elastic properties of amyloid aggregates and their cytotoxicity. In the present paper we utilized the atomic force microscopy (AFM) to visualize and analyze the amyloid fibrils of G26R/[email protected] mutant of N-terminal fragment of human apolipoprotein A-I (apoA-I). The examination of AFM images revealed the existence of two polymorphic forms of apoA-I fibrils – twisted ribbon and helical ribbon. The quantitative analysis of apoA-I elastic properties was performed within the framework of worm-like model of polymer chain using the Easyworm software. The Easyworm package analyzes the images of individual polymer chains obtained by the atomic force microscopy and allows calculation of the persistent length of a chain in three regimes depending on the ratio between the contour and persistent lengths of the polymer. The set of evaluated parameters included the Young’s modulus, persistent length, bending rigidity and the second moment of inertia. All parameters calculated for the helical ribbon conformation were higher than those of the twisted ribbon. These findings suggest that helical ribbon represents a more rigid and mechanically stable configuration. The results obtained may prove of importance for a deeper understanding the mechanics-driven pathological activities of amyloid fibrils.
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