Abstract—A sol–gel method is developed to synthesize ternary indium–gallium–zinc oxide using tartaric acid as an organic complexing agent. The synthesized samples were examined by X-ray diffraction and transmission and scanning electron microscopy. Summarizing the consistent results of these research methods, we can state that the sizes of the particles composing the synthesized samples depend on the synthesis temperature: agglomerates of nanoparticles form at the lowest of synthesis temperatures, and micron-sized particles are detected after sintering at 900°C. The crystallinity of the samples increases with the synthesis temperature. All samples have no impurity crystalline phases and exhibit a uniform indium, gallium and zinc distribution over the sample volume.

The paper presents the results of a theoretical study of the electronic structure and electrical conductivity of single-walled gold nanotubes with chirality indices (4, 0), (5, 0), (6, 0), (7, 0), (4, 4), and (5, 5). The simulations were performed using the density functional theory and the method of nonequilibrium Green’s functions. The Perduew–Burke–Ernzerhof exchange-correlation functional and a two-exponential basis set were used. The importance of using polarized basis sets for the study of electrical properties of gold nanotubes is demonstrated. Analysis of the results showed that the transmission functions of the studied nanotubes depend on their structure in a complex way but, in general, increase with increasing diameter. The dependence of the transmission function on the electron energy does not allow us to speak a priori about the linearity of the current–voltage characteristic of gold nanotubes within a certain finite voltage range. In addition to defect-free single-walled gold nanotubes, gold nanotubes of different diameters with a vacancy-type defect-were also studied. This allowed us to evaluate the effect of such a defect on the atomic structure and electrical conductivity of the single-walled gold nanotubes. It was demonstrated that the conductivity drop can vary within a wide range, correlating with changes in the atomic structure.

The dispersion of metal atoms over the surface of 1D and 2D carbon systems is the most affordable way to control their properties, which are attractive for many applications in electronics, power engineering, and catalysis. In this work, the features of the interaction of titanium atoms with the surface of carbon nanotubes, caused by various structural defects on these surfaces, were studied by first-principles computer simulation based on the density functional theory. Nanotubes (7, 7) and (11, 0) with similar diameters (≈1 nm) but different types of conductivity, metallic and semiconductor, respectively, were chosen for the study. Three types of defects were studied: a single vacancy, a double vacancy, and a topological defect. Two possible orientations of each type of defect relative to the tube axis were considered. We mainly used the basis of atomic-like orbitals (the SIESTA package) and in some test calculations also the basis of plane waves (the VASP package). Computational experiments have shown that the binding energy of Ti atoms with a defect-free nanotube is always lower than with defective ones, regardless of the used approximation for the exchange-correlation functional (LDA or GGA). The binding energies predicted in the LDA approximation are noticeably higher than in the GGA approximation (up to ~15% for the (7, 7) tube and up to ~50% for the (11, 0) tube). The strongest coupling occurs when the titanium atom is adsorbed on a nanotube with a single vacancy. The resulting configuration can be considered as a defect in the substitution of one carbon by a titanium atom.

В работе сообщается об универсальной методике получения наноструктурированных оксидов индия, галлия и цинка золь-гель методом из нитридов соответствующих металлов с использованием этиленгликоля в качестве комлексообразователя. Рентгенофазовый анализ полученных образцов свидетельствует об отсутствии заметных концентраций примесей и о типичных для данных соединений параметрах элементарных ячеек. Микроструктура образцов исследована с помощью электронной микроскопии. По результатам диффузного отражения образцов с использованием метода Кубелки-Мунка определены величины ширины запрещенной зоны и показано, что они находятся в хорошем соответствии с имеющимися литературными данными.

Results are reported about the molecular mechanics simulation of the structures of carbon–nitrogen solid solutions obtained by pyrolysis of a molten mixture of melamine with 50-100 wt.

A universal technique is described for producing nanostructured indium, gallium, and zinc oxides by the sol-gel method from respective metal nitrates with ethylene glycol as a complexing agent. The powder X-ray diffraction analysis of the samples obtained evidences that they do not contain noticeable concentrations of impurities, and their unit cell parameters are typical of these compounds. The microstructures of the samples are studied by electron microscopy. The band gap is determined based on diffuse reflectance of the samples using the Kubelka–Munk method, and it is shown that its boundaries correspond to the available literature data.

The influence of size effects on the properties of a hexagonal boron nitride (h-BN) single layer containing CBVN, NBVN, and OBOBVN defects is studied by ab initio simulation. These defects are potentially capable of generating single photons in quantum optics and quantum information devices. Size effects here mean the dependence of the studied model properties on the simulated fragment size of a 2D structure under periodic boundary conditions. Physically, this means that the properties of a single layer depend on the distance between defects. This dependence allows us to judge how strongly the defects interact with each other and whether they interact at all. For technical applications, the characteristics of the band structure (band gap, spectrum, and density of electron states induced by the defect in the band gap) and the atomic structure of the defect (defect-formation energy, geometry in the equilibrium configuration), which form this band pattern, are important. In this work, these properties are studied using density functional theory with the basis of atom-like functions (SIESTA package) and plane waves (VASP package). The results obtained using both packages are consistent with each other. It is established that the defects can be considered noninteracting, when the distance between them is ten unit-cell parameters.

Приведены результаты моделирования методом молекулярной механики структуры твердых растворов углерод-азот, полученных пиролизом расплавленной смеси меламина с 50-100 масс. % высокотемпературного каменноугольного пека при их медленном нагревании до 500 °С. Экспериментально показано, что электропроводность полученных твердых растворов увеличивается на несколько порядков с ростом концентрации азота от 0,4 до 22 масс. %. Моделирование структуры является важным этапом, необходимым для понимания механизма электропроводности. Исходными данными для моделирования служат результаты элементного, рентгенофазового, пикнометрического, синхронного термического анализов, а также ИК-, и РФЭ-спектроскопии полученных материалов. Помимо атомов азота и углерода в исследуемых образцах присутствуют атомы водорода и кислорода, что объясняется наличием этих элементов в исходных компонентах. Полученные материалы по данным РФЭС и рамановской спектроскопии имеют графитоподобную структуру, с углеродом, находящимся преимущественно в состоянии sp2-гибридизации. Методом РФЭС установлено наличие четырех различных по типу окружения атомов азота: графито-, пиридино-, пирролоподобного, а также окисленного. Данные термического анализа позволили сделать вывод об отсутствии триазиновых островков в образцах, приготовленных из смесей с массовой долей пека 80-100 % и об их присутствии в образцах с массовой долей пека 50-70 %. Данные ИК спектроскопии подтвердили отсутствие амино- и циано- групп во всех твердых растворах. На основании существующих экспериментальных данных предложены модели структуры исследуемых материалов и найдены общие закономерности структур.

Тройной оксид In2O3-Ga2O3-ZnO имеет потенциал применения в электронике. Перспективные методы изготовления транзисторов на его основе требуют наличия методики получения рентгеночистых порошков. В данной статье приводятся сведения о влиянии выбора органического комплексообразователя на морфологию получаемых порошков. Показано, что использование этиленгликоля предпочтительнее, чем лимонной кислоты: полученные с его использованием порошки не содержат посторонних фаз.

The In2O3–Ga2O3–ZnO ternary oxide is prospective for electronics applications. Promising methods of fabricating In2O3–Ga2O3–ZnO based transistors require a technique for the preparation of X-ray pure powders. Data on the influence of the studied organic complexing agent on the morphology of obtained powders are reported. It is shown that ethylene glycol is more preferable to use than citric acid since the powders prepared in the first case contain no admixture phases.

Using the advanced analyses of electron density and fermionic potential, we show how electron delocalization influences the ability of defect-containing graphene to form tetrel bonds. The Cg atoms of a vacancy defect can produce one nonpolar interaction, alongside a peculiar polar Cg⋯Cg bond. The latter stems from the presence of a localized electron pair on a vacancy defect Cg atom and the local depletion of electron localization on another Cg atom. This interaction is an example of intralayer tetrel bond. In the presence of an absorbed molecule of bisphenol A diglycidyl ether (DGEBA), graphene is able to form incipient tetrel Cg⋯O bonds with an ether group oxygen. In contrast to an epoxy group oxygen, the disposition of the ether oxygen often causes the orientation of electron-rich π-domains of graphene carbon on the weakly expressed electrophilic region of the oxygen. In the case of graphene with a point Si defect, the Si atom can form quite strong Si⋯C interactions with the DGEBA aryl carbons. In contrast to other noncovalent bonds, this interaction significantly alters the electron (de)localization on the Si atom and in the aryl ring. The reliability of the obtained results is enhanced by the use of multiple 2D periodic models with defects located at different positions along the DGEBA skeleton.

Modifying the properties of spinel ferrites by doping allows significantly expanding their application in various fields of science and industry. The present work reports results of the study of Ni 1– x Co x Fe 2 O 4 ceramic samples ( x = 0-1 with a step of 0.1) prepared by solid phase synthesis. The morphology and size of the particles of the synthesized powders are determined. The monophase character of the synthesized materials is confirmed by X-ray powder diffraction. The unit cell parameter a,b,c increase from 8.3375(3) Å to 8.3819(4) Å upon the substitution of nickel by cobalt. The differential scanning calorimetry data indicate heat capacity jumps corresponding to a thermal second-order phase transition. The phase transition temperature depends on the ceramics composition and decreases monotonically from 596 °C to 530 °C as nickel is replaced by cobalt.

Легирование с целью модификации свойств ферритов со структурой шпинели позволяет существенно расширить их применение в различных областях науки и производства. В настоящей работе разработан метод твердофазного синтеза керамических образцов ферритов состава Ni1-xCoxFe2O4, где x = 0-1 с шагом 0.1. Определены морфология и размер частиц синтезированных порошков. Рентгенофазовый анализ установил однофазность синтезированных материалов. При замещении никеля кобальтом параметр элементарной ячейки a возрастает от 8.3375(3) до 8.3819(4) Å. Методом дифференциальной сканирующей калориметрии выявлены скачки теплоёмкости, свидетельствующие о температурных фазовых переходах второго рода. Температура фазовых переходов зависит от состава керамики и монотонно уменьшается при замещении никеля кобальтом с 596 до 530 °С.

Методом твердофазного синтеза получены ВЭО BaFe12-x(Ti,Mn,In,Ga)xO19(x=1, x=7). Исследована корреляция химического состава (степень замещения Fe), структурных параметров, магнитных характеристик. Магнитные характеристики ВЭО BaFe12-x(Ti,Mn,In,Ga)xO19 (x=1, x=7) были исследованы в широком диапазоне полей и температур. Измерены инфракрасные спектры коэффициента отражения образцов BaFe12-x(Ti,Mn,In,Ga)xO19 (x=1, x=7), содержащие особенности, связанные с фононными колебаниями. Выполнен качественный анализ зависимости характеристик фононных линий от концентрации x, а также сравнение спектров со спектрами монокристаллического образца состава BaFe12O19.

The BaFe12–x(Ti,Mn,In,Ga)xO19(x = 1, x = 7) HEOs are prepared by a solid-phase synthesis. Correlations between the chemical composition (degree of Fe substitution), structural parameters, and magnetic characteristics are studied. Magnetic characteristics of the BaFe12–x(Ti,Mn,In,Ga)xO19 (x = 1, x = 7) HEOs are studied in a wide range of fields and temperatures. The measured IR reflectance spectra of the samples contain features caused by phonon vibrations. The dependence of characteristics of phonon lines on the concentration x is qualitatively analyzed; the obtained spectra are compared with those of a single-crystal BaFe12O19 sample.

The paper considers the redistribution of the charge density in a carbon nanotube caused by the adsorption of a lithium atom on it. The effective lithium charges were calculated according to the methods of Mulliken, Voronoi, Bader, Hirshfeld, CM5, DDEC6. It is shown that these methods can result in different charge amounts, but the qualitative behavior of the relative charge does not depend on the chosen method. An analysis of the topology of the charge density shows that the interaction of lithium atoms with the tube increases with an increase in the concentration of lithium until the lithium atoms begin to interact essentially with each other.

The article presents the results of a study of the atomic and electronic structure of gold nanotubes that do not have mirror symmetry. The elementary cells of nanotubes (4, 3) and (5, 3) are constructed and their properties are modeled in the framework of the density functional theory using periodic boundary conditions. Different behavior of two types of interatomic distances was established during the “twisting” of the triangular lattice of the nanotube wall. The bonds in first one turned out to be noticeably shorter than in nanotubes with mirror symmetry. The features of the electronic structure and partial densities of electronic states, in general, turned out to be regardless of the presence of mirror symmetry.

A carbon nanotube and a graphene surface with bisphenol A derivatives have been simulated in the DFT framework using periodic boundary conditions. Such compounds are components of epoxy diane resins, which are important composite materials for aircraft structures. The simulation results allow one to state that the use of the specialized exchange-correlation functional Berland and Hyldgaard developed to account for weak Van der Waals interactions is preferable to DFT-D2 method. We observed that the energy of complexes formation depends on the orientation of the functional groups of diglycidyl ether of bisphenol A and determines by whether the surface of the carbon material is flat, like graphene, or curved, like nanotubes. It was found that the strongest binding is observed for nanotubes with a diameter of 1 nm, for which the energy of complex formation is 65 % lower than for the complex of diglycidyl ether of bisphenol A on graphene with the same orientation of functional groups relative to the surface. On the curved outer surface of the nanotubes, the ester derivatives form a greater variety of non-covalent interactions in accordance with the QTAIM analysis of electron density and the energy of complexes formation is lower.

Carbon nanotubes (CNTs) still draw great attention of researchers due to their possible use as anodes for lithium-ion batteries.The capacity of the anode for lithium ions is defined by the efficiency of diffusion of these ions to the adsorption centers located on the outer or inner surface of the nanotubes, as well as between the layers of multi-walled nanotubes.The inner surface can be accessed through the open ends of the tubes or defects in their frame.Moreover, the defects create more efficient adsorption sites than the surface of a perfect tube.This work presents the results of the ab-initio modeling of the lithium adsorption on a carbon nanotube (7, 7) with a vacancy-type defect.The simulation was carried out using density functional theory implemented in the SIESTA package.The Ceperley-Alder exchange-correlation functional and the DZP basis set were used.The formation energies of vacancy defects of two types were determined.Additionally, for each vacancy type, the binding energies of lithium atoms adsorbed inside and outside the CNT (7, 7) near the defect were calculated.These binding energies were shown to be up to twice bigger than on a perfect CNT.The enhancing effect of the vacancy on the CNT sorption activity was found to be wide-ranged: it was observed for adsorption sites in the first and second surroundings of the defect and even for sites located on the tube surface opposite to the defect.