Electron Energy Characteristics Research Articles

Миграция протона по поверхности борных слоев

Borophene is a two-dimensional allotrope of boron and it is also known as boron sheet. First it has been predicted theoretically in the mid-1990s, experimentally borophene was confirmed in 2015 when the structure was successfully synthesized in 2015. One of the key features of borophene is its strong anisotropy – the dependence of mechanical and electrical properties on direction. This phenomenon is not typical for 2D materials and has never been observed in 2D metals before. Borophene has the highest tensile strength of all known two-dimensional materials. In early works, it was found that the adsorption of a hydrogen atom on the surface of borophene is possible and the analyses of electronic density showed that atom H became a proton. Therefore, in this work, the authors have studied the proton migration over the surface of boron sheets of two types and have found the most energetically favorable path of proton motion. The electron-energy characteristics of the process of migration of a single proton along the surface of boron layers of two types are determined and it is established that in all the considered cases the proton is able to move along the surface almost barrier-free. The type of conductivity of pure boron layers and layers modified by a single proton is determined. In the A-type boron layer, the proton increases the band gap by 0.04 eV, and in the B-type layer, the band gap changes by 0.05 eV. It is proved that two-dimensional boron nanostructures can be considered as a new class of boron topological structure with proton conductivity.

Mathematical modeling of the process of interaction of sulfur dioxide with pyrolyzed polyacrylonitrile

The paper presents a study of the interaction of sulfur dioxide with a polymer-pyrolyzed polyacrylonitrile (PPAN). The possibility of using PPAN as an element of an electronic sensor device for recording the presence and identification of sulfur dioxide in the atmosphere is shown. The results of the established geometric and electron-energy characteristics of the polymer interacting with gas are described. Theoretical calculations were performed using the molecular cluster model and the quantum-chemical MNDO method.

Модификация пиролизованного полиакрилонитрила атомами серебра

Recently, the search for new materials for nanoelectronics has attracted the interest of scientists. New materials, which are metal-polymer nanocomposites, can be used in modern electronics. The paper presents the possibility and mechanisms for the formation of a metal composite based on single-layer and two-layer pyrolyzed polyacrylonitrile when interacting with silver atoms. The results of the silver atom adsorption on the polymer surface are described, the possibility of filling the interlayer space with metal atoms is shown, and geometric and electron-energy characteristics are established. Theoretical calculations were performed using a molecular cluster model using a non-empirical method in the STO basis. The structure and electron-energy state of a metal-carbon nanocomposite based on pyrolyzed polyacrylonitrile with silver atoms are studied. It was found that the silver atom is adsorbed on the surface of PPAN, and the adsorption process is almost independent of the selected adsorption center. The introduction of metal atoms into the interplanar space of PPAN causes the initially planar monolayers of PPAN to bend, while the structure retains its stability. It was found that the presence of metal atoms in the PPAN structure causes a change in the band gap, which leads to a change in the conductive properties of the resulting nanocomposite.

Simulation of pyrolysed polyacrylonitrile based composite with amorphising boron additives

The paper deals with the possibility of modifying pyrolyzed polyacrylonitrile with amorphizing additives. Adsorption features of the boron atom on the surface of the monolayer of polymer are studied, and the geometric and electron-energy characteristics of the composite obtained are established. The calculations were performed using the semi-empirical MNDO method within the framework of the molecular cluster model.

Study of electrical and optical properties of a new composite material based on carbon nanotubes and titanium oxide

In this regard, the aim of this work is to study the features of the atomic structure and to predict the electronic energy characteristics of the composite material based on carbon nanotube and ceramic particles – titanium oxide using computer simulation methods. To achieve this goal, the following tasks were solved: construction of a geometric model of the rutile nanoparticle; identification of the energy-stable configuration of the composite based on the carbon nanotube and rutile nanoparticles; determination of the electron-energy characteristics of the composite. The structure of the composite was selected so that the total energy of the composite in absolute value was less than that of the individual tube and rutile the enthalpy of the reaction of the tube and rutile becomes negative, which means that the formation of such a nanocomposite is energetically advantageous. one of the most important applications of such composite is to act as photocatalyst for some chemical reactions because of electrical characteristics and high optical absorption.

Output factors of ionization chambers and solid state detectors for mobile intraoperative radiotherapy (IORT) accelerator electron beams.

PurposeThe electron energy characteristics of mobile intraoperative radiotherapy (IORT) accelerator LIAC ® differ from commonly used linear accelerators, thus some of the frequently used detectors can give less accurate results. The aim of this study is to evaluate the output factors (OFs) of several ionization chambers (IC) and solid state detectors (SS) for electron beam energies generated by LIAC ® and compare with the output factor of Monte Carlo model (MC) in order to determine the adequate detectors for LIAC ®.MethodsThe OFs were measured for 6, 8, 10, and 12 MeV electron energies with PTW 23343 Markus, PTW 34045 Advanced Markus, PTW 34001 Roos, IBA PPC05, IBA PPC40, IBA NACP‐02, PTW 31010 Semiflex, PTW 31021 Semiflex 3D, PTW 31014 Pinpoint, PTW 60017 Diode E, PTW 60018 Diode SRS, SNC Diode EDGE, and PTW 60019 micro Diamond detectors. Ion recombination factors (k sat) of IC were measured for all applicator sizes and OFs were corrected according to k sat. The measured OFs were compared with Monte Carlo output factors (OFMC).ResultsThe measured OFs of IBA PPC05, PTW Advanced Markus, PTW Pinpoint, PTW microDiamond, and PTW Diode E detectors are in good agreement with OFMC. The maximum deviations of IBA PPC05 OFs to OFMC are −1.6%, +1.5%, +1.5%, and +2.0%; for PTW Advanced Markus +1.0%, +1.5%, +2.0%, and +2.0%; for PTW Pinpoint +2.0%, +1.6%, +4.0%, and +2.0%; for PTW microDiamond −1.6%, +2%, +1.1%, and +1.0%; and for PTW Diode E −+1.7%, +1.7%, +1.3%, and +2.5% for 6, 8, 10, and 12 MeV, respectively. PTW Roos, PTW Markus, IBA PPC40, PTW Semiflex, PTW Semiflex 3D, SNC Diode Edge measured OFs with a maximum deviation of +5.6%, +4.5%, +5.6%, +8.1%, +4.8%, and +9.6% with respect to OFMC, while PTW Diode SRS and IBA NACP‐02 were the least accurate (with highest deviations −37.1% and −18.0%, respectively).ConclusionThe OFs results of solid state detectors PTW microDiamond and PTW Diode E as well as the ICs with small electrode spacing distance such as IBA PPC05, PTW Advanced Markus and PTW Pinpoint are in excellent agreement with OFMC. The measurements of the other detectors evaluated in this study are less accurate, thus they should be used with caution. Particularly, PTW Diode SRS and IBA NACP‐02 are not suitable and their use should be avoided in relative dosimetry measurements under high dose per pulsed (DPP) electron beams.

COMPARISON OF SENSOR ACTIVITY IN CARBON NANOTUBES MODIFIED WITH FUNCTIONAL GROUPS

This article presents a theoretical study of sensor activity of nanosystems based on carbon nanotubes modified with functional groups (carboxyl, aminogen, nitrogroup) for some metal atoms and ions. Calculations have been performed within the frameworks of a molecular cluster model with the use of the semiempirical MNDO method and the density functional theory DFT. The mechanism of functional group binding to the open border of single−walled zig− zag carbon nanotubes leading to the formation of chemically active sensors on their basis has been investigated. Main geometric and electron energy characteristics of the resultant systems have been defined. Interaction of the sensors so synthesized with atoms and ions of some metals, e.g. potassium, sodium and lithium, has been analyzed.

Sensor activity with respect to alkali metals of a carbon nanotube edge-modified with amino group

The work is devoted to the theoretical study of sensor activity of nanosystems based on a carbon nanotube modified with a functional amino group, with respect to certain metal atoms and ions. The calculations were performed within the molecular cluster model using the semiempirical MNDO scheme and density functional theory DFT. The mechanism of attachment of an amino group to the open edge of zigzag single-walled carbon nanotubes possessing cylindrical symmetry was studied to design a chemically active sensor based on them. The key geometric and electron-energy characteristics of the constructed systems have been determined. The interaction of the sensors thus constructed with atoms and ions of some metals—potassium, sodium, and lithium—has been studied. The scanning of arbitrary surfaces containing selected atoms or ions has been modeled; from the interaction energies, and the activity of the single-walled carbon nanotube + amino group probe system has been determined with respect to the selected elements to be initialized. Analysis of the charge state of the system has established that the sensor action mechanism is realized, as a result of which the number of charge carriers in the resulting nanotubular system serving as a sensor probe changes, which provides the appearance of conductivity in the system. The presence of metallic atoms can be experimentally detected by the change in the potential in a probe system based on a nanotube with a functional group. The theoretical studies have proved the possibility of creating highly sensitive sensors based on the most promising nanomaterial— carbon nanotubes functionalized with active chemical groups, including the amino group NH2.

Nuclear induces effects and mass correlations in low and multiply charged helium-like ions

The ground-state electron energies, the mass correction and mass polarization of low and multiply charged helium-like ions are analytically and numerically calculated. Approximately 3500 different kinds of ions with charge Z = 2 ÷ 118 are considered. The two-electron Schrodinger equation was solved using a discrete variational-perturbation approach developed by the authors and based on explicitly correlated wave functions. This approach takes into account the motion of the nucleus and yields accurate values for the electron characteristics. The results are presented with and without the inclusion of the mass polarization in the minimization procedure. The relative importance of mass correlations and relativistic effects in the formation of the electron energy characteristics of the helium-like ions are studied for different values of Z. The role of the inclusion of the mass polarization in the minimization procedure as an instrument to present and take into account the effects induced by the nuclear properties, structure and characteristics has been shown.

Electron energy spectrum of two-dimensional hydroxysiloxane structures with defects of substitution of silanol groups with boron, aluminum, and gallium atoms

A computational scheme based on density functional theory, generalized to the case of periodic structures, is used to calculate the electron energy characteristics of two-dimensional hydroxysiloxane structures both of ideal structure and with defects induced by the substitution of surface silanol groups with GroupIII atoms (B, Al, Ga). The dependences of the energy-band parameters and the position of the chemical potential and optical absorption spectra on the defect concentration are analyzed in the energy range of absorbed photons ћω < 17 eV. It is shown that the energy of the electron transition from the np band to both the conduction band and to acceptor states resulting from the introduction of Group-III atoms into the hydroxysiloxane structure can be adjusted by varying the degree of substitution of silanol groups. The results can be used for the selection of film materials with the desired electron energy spectrum for microand nanoelectronics technology.

Electron energy and optical characteristics of two-dimensional graphene boronitride structures

The density functional theory (DFT) calculation scheme that explicitly included or neglected dispersion interactions and was adapted for systems with translational symmetry was used to calculate the electron energy spectra and the optical absorption curves of finite-layer graphene boronitride structures. Explicit inclusion of dispersion interactions considerably affected the calculated energy gains resulting from the formation of alternating graphene boronitride layers. The energy gap between the occupied and vacant states was very small or absent in these structures. In the optical absorption spectra of multilayer structures, the bands inherent in monolayer graphene and boronitride structures appeared (with a slight shift) depending on whether the number of layers was even or odd; in the case of the odd number of layers, this depended on whether the graphene or boronitride planes were “external.”

Electron energy spectrum and the specific features of the optical absorption of solid solutions of magnesium, aluminum, and boron oxides

A calculation scheme based on density functional theory, generalized for the case of periodic structures, is used to calculate the electron energy spectrum of binary and ternary oxides of magnesium, aluminum, and boron with MgBxAl2−xO4 spinel structure. The dependences of the electron energy and geometric characteristics of the studied structures on the degree of substitution x are examined. It is shown that, by changing this parameter (i.e., the composition of the ternary oxide), it is possible to adjust the bandgap width and the position of the chemical potential for boron-magnesium-aluminum spinel. The dependence of the imaginary part of the relative permittivity on the energy of absorbed photons is obtained and analyzed.

Electron-energy characteristics of double-walled carbon nanotubes doped with alkali metal atoms

A computational scheme based on density functional theory adapted for systems with translational symmetry is applied to calculating the electronic structure and energy spectrum of double-walled carbon nanotubes doped with alkali metal atoms (Li, Na, and K). The specific features of the electron-energy characteristics, including the potential curves for the interaction of nanotubes with “guest” atoms moving in the radial direction or along the circumference of the tube, are established. It is shown that doped double-walled nanotubes have an increased electron emissivity.

Electron energy characteristics and one-electron state spectra of surfaces of molybdenum oxide and solid solutions thereof with niobium and technetium oxides with fluoropolymer coatings

The energy spectra of electrons belonging to the surface centers of molybdenum oxide and its solid solutions (interstitial phases) with niobium and technetium oxides have been analyzed. The densities of one-electron states and their atomic orbitals have been calculated for hydroxyl, dehydroxyl, and fluoropolymercoated surfaces. The calculation method is based on the density functional theory using the three-parameter hybrid Becke-Lee-Yang-Parr exchange-correlation potential in the basis 3-21G of linear combinations of Gaussian orbitals.

Internal investigation of saturation carbon nanotubes molecular hydrogen

The electron-energy characteristics of the saturation of the cavity of carbon nanotubes of armchair and zig-zag types with molecular hydrogen are theoretically studied. The calculations are performed based on a model of a molecular cluster with the use of the MNDO and PM3 methods, which proved to be effective in predicting the electronic structure of molecules and periodic solids. Two mechanism of saturation of the cavity of single-walled carbon tubulenes with hydrogen molecules were proposed and examined: (1) the mechanism of surface wetting and (2) the capillary mechanism of filling.

Semi-Empirical Investigation of Boron Nanotubes and Some Structure-Modification Composites on Their Base

Computations of single-walled boron nanotubes (n, n) and (n, 0) types have been carried out within the framework of the Ionic-Building Covalent Cyclic Cluster model and semi-empirical quantum-chemical MNDO scheme. The basic electron-energy characteristics of boron nanotubes have been found and boron nanotubes with various defects were investigated.

Electron-energy characteristics and the spectrum of one-electron states of the surfaces of ferric and nickel oxides with fluoropolymer coatings

A cluster model and a calculation scheme based on the density’ functional theory (the three-parameter hybrid exchange-correlation Becke–Lee–Ya ng–Parr potential, the split-valence double-zeta basis, and the effective core’ pseudopotential for transition-element atoms) are used in the calculation of processes occurring during the formation of fluoropolymer coatings on the surfaces of ferric and nickel oxides. The electronic spectra of the hydroxidized, dehydroxidized, and fluoropolymer-coated surfaces of the oxides under study are analyzed.

Semiempirical studies of the electronic structure of aluminophosphide and Haeckelite boronitride nanotubes

The paper presents the results of semiempirical quantum-chemical calculations of the electron energy characteristics of Haeckelite boronitride nanotubes (n, n)-BN468 (n = 3, ..., 14), (n, n)-BN48 (n = 3, ..., 11), and (n, n)-BN57 (n = 4, 5, 6). The nanotubes were found to be dielectrics with forbidden band widths from 5.5 to 8 eV. The forbidden band energy of the nanotubes increased as their diameter grew. The influence of substitution defects on the physical properties of Haeckelite boronitride nanotubes was studied for the example of the carbon atom.

Modulation of optical absorption in poly(diphenylenephthalide) films near the switching threshold

Optical properties of poly(diphenylenephthalide) nonconjugated polymer films near the electronic switching threshold have been studied by modulation spectroscopy. The measured spectra exhibit specific features in the range of the band gap at ∼2.4 eV. The results obtained have been interpreted using quantum-chemical calculations of the electron energy characteristics of the polymer molecule. It has been established that the injection of charge carriers into the polymer film and interaction of this excess charge with the macromolecule can lead to the formation of deep trap states near the center of the band gap.

Emission characteristics and parameters of a glow discharge in an argon-xenon-chlorine mixture

We present the results of a study of the emission characteristics of a low-pressure longitudinal glow discharge in an Ar-Xe-Cl2 mixture (p = 0.5–6.0 kPa) and numerical modeling of its plasma parameters as a function of the parameter E/P. We optimized the average emission power of the discharge in the spectral range 160–310 nm as a function of the discharge current, the pressure and composition of the gas mixture. The plasma parameters were calculated for the optimal mixture (according to experimental data) and included obtaining the dependences of the electron transport and energy characteristics, the power losses per unit pressure in the discharge going toward elementary electron processes in the plasma, and also the ionization and attachment coefficients as a function of the parameter E/P. The results of numerical modeling of the glow discharge parameters allow us to provide a qualitative basis for the emission distribution in the spectrum of a plasma based on an Ar-Xe-Cl2 mixture.