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For the first time, this study conducts a computational analysis by employing density functional theory (DFT) to investigate the effects of silicon doping as substitutional defects on the structural, electronic, and magnetic characteristics of the L10-FeNi alloy. The aim of this study was to explore the potential applications of Si-doped FeNi compounds as alternatives to rare-earth permanent magnets. For this, we have performed full potential calculations of L10-FeNi with substitutional Si-doping within a generalized gradient approximation. Two types of substitutional Si-doping (ONi/OFe) in the Ni/Fe site of the parent alloy have been investigated. The computed formation energy (Ef) indicates that the incorporation of silicon defects increases the structural stability of tetragonally distorted L10-FeNi. Moreover, our findings demonstrate that the FeNi:Si(ONi) in the L10-structure has a stable saturation magnetization (Ms), whereas the FeNi:Si (OFe) has a small reduction in Ms. Therefore, Si-substituted FeNi alloys can be tuned to become a good candidate for permanents magnets.

The Ag8SnS6 crystal was synthesized by directly melting a high-purity stoichiometric mixture of elementary Ag, Sn, and S in a sealed quartz ampoule. This argyrodite crystallizes in the orthorhombic structure (Pna21 space group (No. 33)) at room temperature. The theoretical first-principle calculations of the electronic band structure and density of states of a αʹʹ-Ag8SnS6 crystal are estimated by the generalized gradient approximation (GGA) and local density approximation (LDA). A Perdew–Burke–Ernzerhof functional (PBE) and (PBEsol) were utilized for GGA calculation. All calculated parameters correlate well with known experimental data. Based on the electronic band structure, the effective mass of electrons and holes was calculated. The anisotropic behavior of electronic band structure is discussed.

The solid-state Cd0.75X0.25Te (X= Cu, Ag, and Au) solutions crystallize in the cubic structure and are studied in the framework of density functional theory. The theoretical first-principle calculations of the electronic band structure, density of states, and refractive index of solid-state Cd0.75X0.25Te (X= Cu, Ag, and Au) solutions are estimated by the generalized gradient approximation (GGA). A Perdew–Burke–Ernzerhof functional (PBE) was utilized. Formation energy is calculated based on the results of the total energy of the study samples. The effective mass of the electrons and holes was calculated based on the electronic band structure. The influence of atom substitution on electron conductivity and mobility is discussed. To study the optical properties was use a complex dielectric function ε(ħω). The spectral behaviour of the refractive index was calculated based on the dielectric function.

In the study, band structure calculation in the points of high symmetry of the first Brillouin zone and alongside the lines that connect them has been derived by using CASTEP programs in which the pseudopotential method with the basis in the form of plane-waves is realized. The calculated value of the lattice parameters using GGA functional is well correlated with experimental data. According to the band diagram that was built for the Ag3AsS3 crystal using GGA method, band gap has an indirect type. The calculated value of the band gap is = 1.22 еV. The experimental value of the band gap obtained by Tauc’s method is = 2.01 еV, = 2.17 еV. Full and partial density of N(E) states for contributions of separate atoms has been calculated. As a result, the top of the valence band is formed by 3p-states of S atoms and the bottom of the conduction band is formed by 5s-states of Ag atoms and 3p-states of S atoms.

Theoretical concepts of the positron annihilation process in structural materials of nuclear reactors, taking into account the peculiarities of their electronic structure, have been developed. The Tao - Eldrup model, which allows to analytically calculate the lifetime of a positron in a spherically symmetric potential well, has been modified for the case of a potential well of finite height, in order to expand the limits of the model's application. The dependence of the positron lifetime on the height and width of the potential well, which occurs at the point defects, was determined. The results obtained within the framework of the modified model provide important information for the analysis of positron lifetime spectra in irradiated materials and data for the verification of quantitative calculations by the method of density functional theory. [ABSTRACT FROM AUTHOR]

First-principles computations of the electrical characteristics of AlAs have been carried out using the density functional theory-DFT and the Local Density Approximation-LDA,methods (DFT) and Generalized Gradient Approximation-GGA. We utilized the CASTEP's plane wave basis set implementation for the total energy computation (originally from Cambridge Serial Total Energy Package). We used to look at the AlAs structure's structural parameter. The band gap was overestimated by the Generalized Gradient Approximation and LDA techniques, although the band gap predicted by the GGA is more in line with the experimental finding, according to the electronic structure calculation utilizing the two approximations. A semiconductor with a straight band-gap of 2.5 eV is revealed by the GGA calculation. The energy band diagram is used to calculate the total and partial densities of AlAs states. Multiple configurations of the ionic model were calculated. of Al+xAs−x (0.0 ≤ x ≤ 1) are also performed utilizing free-atom profiles. According to the ionic model, 0.75 electrons would be transferred from the valence 5p state of aluminum to the 3p state of Arsenide.

Among the family of currently known promising quasi-two-dimensional (2D) materials, the authors of this survey concentrate on the problem of functionalization of the graphene- and phosphorene-based structures. In most cases, the modification of their properties occurs through the covalent or noncovalent surface functionalization and mechanical affects. The atomic structures and some physicochemical features of 2D materials possessing novel properties as compared to their bulk counterparts are analysed. Their main advantages are the thickness of one or more atoms, the absence of surface-broken bonds, high mobility of charge carriers, the flexibility, the ability to be combined artificially into coplanar (lateral) or lamellar heterostructures, as well as the possibility to manipulate widely the band-gap changing from the semi-conducting state even into the semi-metallic one (or vice versa) when needed. In order to reveal new factors affecting the electronic properties of 2D materials by means of the computational experiment using the author’s (self-constructed) software code, a series of studies are carried out. They are the calculations of the spatial distribution of valence electrons’ density, the electron densities of states, the band-gap widths, Coulomb potentials along selected directions, the charge values in regions of different-size material, the dielectric matrices, the macroscopic relative permittivities, and absorption spectra. A series of recent studies, which the authors carried out modelling the electronic and transport properties of single- or multilayer graphene films subjected to deformation or/and magnetic fields and containing different-type (point- or/and linear-acting) defects is reviewed. Analysing the obtained results and revealed effects, it is claimed that the uniaxial tensile deformations or shear deformations along with their combinations as well as the structural imperfections (mainly, the mutually configured defects) can be useful for achieving the new level of functionalization of graphene. So, for modification of its electrotransport properties through tuning the band-gap value as much as it is enough to achieve the graphene transformation from the zero-band-gap semi-metallic state into the semi-conducting state and even reach the gap values, which are substantially higher than that for some materials (including silicon) currently used widely in the nanoelectronic devices. The strain- and defect-induced electron–hole asymmetry and anisotropy of conductivity and its nonmonotony as a function of deformation suggest a confidence in manipulating the electrotransport properties of graphene-like and beyond quasi-2D materials through a variety of both strains and defects. The use of reviewed and analysed results serves as a significant step in improving the properties of the considered materials in order to implement the multifunctional applications of them in the immediate prospect.

Electronic and phonon band structure, thermodynamic and optical properties are studied for the CdTe crystal. We calculated the electron and phonon dispersion at high symmetry directions, density of electron and phonon state, temperature dependence feature of Raman spectra, heat capacity, free energy, entropy, enthalpy and Debay temperature estimated with the generalized gradient approximation (GGA). A Perdew–Burke–Ernzerhof functional (PBE) was utilized. To study the optical properties was use a complex dielectric function ε(ħω). All of the calculated parameters correlate well with the known experimental data.

In this paper, density functional theory (DFT) study was applied to the absorption of BMSF-BENZ ((4-bromo-7-methoxy-1-(2-methoxyethyl)-5-{[3 (methylsulfonyl)phenyl]methyl)}-2-[4-(propane-2)) yl)phenyl]-1H-1,3-benzothiazole) used for the treatment of Osteoporosis, on the surfaces of two types of nanocages Zn12O12 and Al12P12. The results showed that the interaction of BMSF-BENZ with the nanocages was highly exothermic, indicating the high chemical adsorption of the new complexes. The adsorption energies of the ZnO nanocage were higher than those of AlP for all the active atoms investigated on the drug compound (Br, N8, N9, N58, O35, O42, and S). Topology analyses such as QTAIM and NCI/RDG indicate that the interactions between the BMSF-BENZ drug and the surface of the ZnO nanocage are more substantial than that of the AlP nanocage. The obtained results of charge, the total density of states (TDOS), and boundary molecular orbital analysis confirm a characteristic orbital hybridization upon adsorption of BMSF-BENZ, indicating the potential application of AlP as a biochemical adsorbent for BMSF-BENZ. However, ZnO nanocage is a candidate for drug delivery applications.

The electronic band structure of the solid-state CdSe0.5S0.5 thin film solution in the framework of the density functional theory calculations is investigated. The structure of the sample is constructed on the original binary compound CdS, which crystallizes in the wurtzite phase. Transformations of the electronic energy spectra for the solid-state CdSe0.5S0.5 solution, which occur in the process of transition from bulk crystals to thin films, are analyzed. The refractive index and high-frequency dielectric constant are calculated. All of the calculated parameters correlate well with the known experimental data.

In order to develop approaches to predict the spectral properties of organic dyes for solar cells the test calculations of typical π-conjugated systems with various structural fragments, have been performed. Among the structural elements there are benzene, oxazole, oxsadiazole, thiophene and coumarin fragments. Nitro, methoxy, dimethylamino and diethylamino groups are substituents. According to the obtained experimental data, the diethylamino group at position 7 of the coumarin moiety gave the highest bato- and hyperchromic shifts of spectra. Experimental absorption spectra were measured in various solvents with different polarity. Among them are cyclohexane, dimethoxyethane, tetrahydrofuran, methanol, acetonitrile, and dimethylsulfoxide. It has been shown that there are no significant changes in the λ(max) absorption of coumarin-based compounds when the solvent is changed to a more polar one, but there is a noticeable tendency to increase the intensity of the absorption spectra. For the theoretical interpretations of electronic spectra absorption ab initio density functional theory (DFT) as well as semi-empirical methods (PPP/CIS, ZINDO/S, AM1/CIS) were used. In the DFT calculations the functionals B3LYP, CAM-B3LYP, M06-2x, PBE1PBE, wB97XD were used. A significant discrepancy in the estimations of electronic excitations is demonstrated by the DFT for the different functionals. It is concluded that DFT calculations should be performed by using both B3LYP and CAM-B3LYP (or M06-2x) functionals. Linear response theory has been used to evaluate the solvatochromic properties of π-conjugated compounds in the DFT frameworks. In general it was found that semi-empirical approaches especially π-electron method PPP/CIS and all valence method ZINDO/S can provide adequate estimations of excitation energies of π-conjugated dyes for moderate computer resources.

Cadmium sulfide (CdS) crystal is a representative of AIIBVI crystal group and exhibits typical semiconductor behavior. CdS crystal can exist in either zinc-blende or hexagonal (wurtzite) structures under normal conditions, depending on the growth conditions. These crystals remain an important research Field because of their wide application in various Fields of optoelectronic devices. From this point of view, the study of structural properties and the dynamics of electronic spectra of CdS crystal under the action of external pressures is of fundamental interest for studying the process of stabilization in compounds. We have investigated the effect of pressure on the electronic band structure of CdS crystal using the density functional theory. In this approach, the generalized gradient approximation (GGA) and the Purdue-Burke-Ernzerh of (PBEsol) parameterization were used for the exchange-correlation potential calculation. The ground-state properties were determined for the bulk material (CdS) in zinc blende structure. Structural and electronic properties were studied in the range of hydrostatic pressures between 0 and 90 GPa. The electron band-energy structure and density of states were calculated at different pressures. The equilibrium structural parameters, bulk modules and bandgaps were calculated and compared with the available experimental data and other theoretical results. The effect of pressure on the energy gap, total energy, and lattice parameters of CdS crystal has been determined and compared with other known data. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) materials are currently gaining a lot of interest due to excellent properties that are different from their bulk structures. Single and few-layered of Transition metal dichalcogenides (TMDCs) have a bandgap that ranges between 1-2 eV, which is used for FET devices or any optoelectronic devices. Within TMDCs, a ton of consideration is focused on Molybdenum Disulfide (MoS2) because of its promising band gap-tuning and transition between direct to indirect bandgap properties relies upon its thickness. The density functional theory (DFT) calculations with different functionals and spin-orbit coupling (SOC) parameters were carried out to study the electronic properties of bulk and monolayer MoS2. The addition of SOC brought about a noteworthy change in the profile of the band energy, explicitly the splitting of the valence band maximum (VBM) into two sub-bands. The indirect bandgap in bulk MoS2 ranges from 1.17- 1.71eV and that of the monolayer bandgap was 1.6 – 1.71eV. The calculated parameters were compared to the obtained experimental and theoretical results. The obtained density of states (DOS) can be used in explaining the nature of bandgap in both the bulk and monolayer MoS2. These electronic characteristics are important for applications in material devices and energy-saving applications

In recent years, inorganic cesium lead bromide (CsPbBr3) perovskite has been widely studied due to its potential spplication in light-emitting devices and solar cells. In this work, within the density functional theory framework, we performed a study of structural and electronic properties of temperature-dependent phases of the CsPbBr3 crystal, in particular, the cubic, tetragonal, and orthorhombic phases using different approximations for the exchange-correlation functional. The analysis of structural parameters shows that the lattice constants and the volume of the unit cell change when the CsPbBr3 crystal changes from the cubic phase to the tetragonal and orthorhombic structures. A good agreement between theoretical and experimental results is obtained using GGA(PBEsol) and GGA(PBEsol)+U approximations. The Mulliken population analysis indicates that between Cs and Br atoms there is a stronger ionic bonding and at the same time there is a stronger covalent bonding between Br and Pb atoms. The electronic structure of CsPbBr3 perovskite was investigated by estimating the change in the electronic properties when included in the calculations of spin-orbit coupling (SOC). The results of the calculations of the band-energy structure showed that the cubic, tetragonal, and orthorhombic crystalline phases of perovskite are semiconductors and have direct bandgaps. Also, we found that the bandgap changes with a change in the phase structure. The obtained values of the bandgap for all crystalline phases of CsPbBr3 perovskite are in good agreement with the previously obtained theoretical calculations as well as experimental data. We established that the tilting angle has a crucial effect on the bandgap width of the tetragonal and orthorhombic phases. The results of the obtained first-principle calculations show a wide temperature range of the possible use of CsPbBr3 perovskite. [ABSTRACT FROM AUTHOR]

Context. The paper presents a computational scheme and a number of techniques for increasing the efficiency of mathematical modeling of the energy characteristics of metal clusters with vacancies. The object of the research is the process of calculating wave functions and finding eigenvalues using the Numerov and the shooting methods. Objective. The objective of the research is to improve the quality of the calculation of the wave functions of electrons in a metal cluster by using optimally selected methods and techniques in the computational scheme, to ensure the adequacy, stability and cost-effectiveness of self-consistent calculations of the energy characteristics of metal clusters by limiting the change in the electrostatic potential within a single iteration, choosing the optimal integration step and data presentation format. Method. At the modeling stage, to increase the efficiency, the electron Density Functional Theory was used in conjunction with the Kohn-Sham version for the stabilized jellium model taking into account the local density approximation for calculating the energy characteristics of nanoclusters. At the simulation stage, the one-electron wave function was calculated by “stitching” it from two parts at an empirically selected point with normalization before and after the procedure. A number of techniques have been developed to improve the quality of the simulation: calculating the optimal step, limiting changes in the electrostatic profile, managing the resulting data arrays, etc. For calculations on a supercomputer, the distribution between the flows was carried out. Results. At the modeling stage, economic models of the metal sphere with a vacancy in the center were developed. For the simulation stage, a method of stable two-sided calculation of the wave function using the shooting and the Numerov methods with the optimal step has been developed. The full computational scheme for the simulation is implemented in C ++ for calculation on a PC and on a supercomputer. The simulation results were compared with the \emph{ab-initio} calculation data and experimental data for Cs, Rb, K, Na, Li, Mg, and Al clusters with and without vacancies (calculation error < 15\ Conclusions. The developed computational scheme and modeling technique allow increasing the simulation efficiency and obtaining adequate energy characteristics of metal spherical nanoclusters with and without vacancies. Further research might focus on the modification of models and simulation techniques for the study of layered nanoscale systems. [ABSTRACT FROM AUTHOR]

Studying interaction of zinc (II) with silica and alumina-silica surfaces is important for several reasons. From a practical point of view, it is carried out in the framework of the creation of a medicinal product, the ingredients of which are, in particular, silica(alumina)containing sorbent and zinc compound; from a theoretical point of view, it is a search for the adsorption patterns on the mentioned surfaces in a series of d-elements with a close electronic structure (zinc, copper, nickel, cadmium, etc.). In addition, it is advisable to supplement the experimental adsorption data with the results of quantum chemical simulation of the structure and formation energy of zinc (II) complexes with active surface centers. Adsorption of Zn2+ ions from a neutral aqueous solution on silica and alumina-silica materials was studied by means of the method of adsorption isotherm. The specific surface of the materials was determined by method of thermal desorption of argon. Quantum chemical analysis of the structure and energy of formation of the hydrated zinc sulfate ion pair on silica and alumina-silica surfaces was performed by means of Hartree-Fock-Roothaan method with extended basis set 6-31++G(d,p). According to the magnitude of adsorption (A) of zinc, the test materials are divided into three groups: 1) enterosgel, kaolin, nanosilica A-300 and polymethylsiloxane, for which Аmax is from 0.15 to 0.3 mg/g; 2) Syloid® 244 FP, KG-60 and KG-40, aminopropylaerosil, smectite (Аmax from 1.2 to 12.0 mg/g); 3) zeolites NaA-TK-1173 and NaX (Аmax more than 30 mg/g). It is concluded that the high adsorption activity of zinc(II) is primarily due to the presence of developed porous structure. The most probable places of interaction between hydrated zinc ions and hydroxyl group of silica and alumina-silica surfaces are determined by means of quantum chemical simulation. The pKMe values have been calculated of ion exchange of silica surface when interacting with Zn2+ cations. [ABSTRACT FROM AUTHOR]

Nanoporous phases or polymorphs are different inorganic solid structures of the same composition with corresponding bulk crystal usually have vary properties and applications. Thereby, synthesizing or predicting new classes of nanophases for an individual compound are of extensive significance and have been attaining appreciable interest. A few assembled nanoporous phases (SOD, LTA and FAU) based on fullerene-like nanoclusters of ZnO with novel structures and properties have been predicted using a ‘bottom–up’ approach within the density functional theory with Hubbard corrections for Coulomb interaction (GGA + U method). Among these structures, three phases are reported for the first time (CAN, LOS and FRA), which could considerably extend the family of nanoporous phases of ZnO. We also show that all these nanoporous phases can be classified analogically to the aluminosilicate-zeolites’ inorganic openframework compounds. The structural and electronic properties of these nanoporous ZnO phases have been investigated. The hollow cage structures of the appropriate building block are well saved in all of them that leads to their high elasticity and flexibility as well as low-density nanoporosity. Furthermore, the electronic properties of the separate components are also preserved. The band analysis detects that these new nanophases are semi-conductive with large value of band gap comparing to a bulk crystal of ZnO. We suggest that nanoporous character of such structures could be applied as a band-gap engineering method for morphologically and electronically oriented functional materials. Furthermore, due to nanoporosity of these phases, it could be used for gas separation, heterogeneous catalysis, water purification, batteries, etc. In addition, such researches provide a basis for further successful building of other nanoporous phases of semiconducting II–VI compounds, where different nanophases might be also observed. [ABSTRACT FROM AUTHOR]

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The purpose of this work is to determine the influence of spin-orbital interaction on the electronic energy spectrum of CsPbBr3 and CsPbI3 crystals. The goal was achieved in the following sequence. At the first stage, partial densities of electronic states were calculated and a symmetrical analysis of the electronic structure of the crystals was performed. The calculations were made from the first principles in the formalism of the density functional theory in the basis of the projector augmented waves (PAW). The semilocal exchange-correlation potential derived within the generalized gradient approximation (GGA) was used in the calculations. At the second stage, the electronic energy bands were obtained without taking into account the spin-orbital interaction. The third stage consisted in obtaining the electron energy spectrum of the crystals including the spin-orbital interaction in the calculation scheme. A significant influence of the spin-orbit interaction on the values of the interband gaps ∆E(k) of both crystals has been revealed. In particular, it has been found that the spin-orbit interaction reduces interband gaps in the CsPbBr3 crystal at the points Γ, X, M and R of the first Brillouin zone by 0.17, 0.22, 0.66 and 1.01 eV, respectively. In the CsPbI3 crystal, the reduction of interband gaps at the same points was found to be 0.31, 0.25, 0.73 and 1.08 eV, respectively. Such significant dependence of the parameter ∆E(k) on the momentum indicates a strong non-locality of the spin-orbital interaction operator of CsPbBr3 and CsPbI3 crystals. Consequently, it is not justified to compare the calculated parameters of the electron energy spectrum obtained without the spin-orbital interaction for CsPbBr3 and CsPbI3 crystals with the experiment. Neglecting the spin-orbit interaction can lead to significant errors in the calculation of the optical constants of crystals containing heavy elements. The obtained parameters ∆E(k) can be used to correct the values of the interband gaps of CsPbBr3 and CsPbI3 crystals found without taking into account the spin-orbital interaction on the basis of other theoretical methods. [ABSTRACT FROM AUTHOR]

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The stereochemical aspects of epoxidation of norbornene and its 7-syn-substituted derivatives by performic acid were investigated. Geometry and thermodynamic parameters of transition states and prereactive complexes were computed at the UBHandHLYP/6-31G(d) level of theory. It is shown that the transition states have a pronounced biradical character and a nearly coplanar orientation of the C=C bond and the molecule of performic acid. Transition state analysis revealed that, in the case of the syn-7-hydroxy derivative, the preference for the exo-approach of the oxidant can be explained by the stabilization of transition state with hydrogen bonding. In contrast, a chlorine atom or a methyl group at the 7-syn position facilitated the formation of endo-epoxides due to steric repulsion between the substituent and the oxidant.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)