Electronic States Of Atoms Research Articles

First-principles calculations of electronic, vibrational, and thermodynamic properties of nitrogen-rich salt of 3,6-dinitramino-1,2,4,5-tetrazine [(DAG)2(DNAT)·H2O

In recent years, nitrogen-rich salts as green and efficient energetic materials have garnered widespread attention. This study focuses on a novel green synthesized salt, (DAG)2(DNAT)·H2O, which obtained through DNAT synthesis. Employing first-principles calculations, we conducted theoretical investigations to elucidate the electronic structure, vibrational, and thermodynamic properties of (DAG)2(DNAT)·H2O. Our computed lattice parameters align with experimental values from literature data. Analysis of the band structure and electronic states of atoms within the compound was performed. Vibrational modes for each peak in the infrared and Raman spectra were meticulously described, accompanied by phonon dispersion curves and phonon density of states plots for phonon contribution analysis. Thermochemical functions including enthalpy (H), heat capacity at constant volume (CV), Helmholtz free energy (F), Debye temperature (θ), and entropy (S) were computed based on vibrational characteristics, providing essential references for future research endeavors.

MOSSBAUER STUDIES OF NATURAL MINERAL RAW MATERIALS OF KAZAKHSTAN FOR BAUXITE-BASED PROPPANTS

The main problem at the oil and gas field is hard-to-recover reserves. The article discusses promising modern methods of increasing oil recovery. The analysis of widely used methods of extraction of hard-to-recover oil and gas reserves is carried out. The Mossbauer studies of the domestic natural mineral raw materials of proppants based on bauxite and aluminum oxides were carried out in order to study the structural and phase features of these materials. Proppants used in hydraulic fracturing to hold cracks play an important role in the oil and gas industry. The Moessbauer method is a powerful tool for studying the structure and electronic state of atoms in materials. It is based on the phenomenon of nuclear gamma resonance absorption and provides information about the chemical environment of the nucleus. In this study, proppants based on bauxite and aluminum oxides were used, which were subjected to a Mossbauer analysis.

Constructing oxygen vacancy-rich MXene @Ce-MOF composites for enhanced energy storage and conversion

Oxygen vacancies can regulate the coordination structure and electronic states of atoms, thus promoting the formation of surface-active sites and increasing the conductivity of the electrode material. This work presents a design for MXene@Ce-MOF composites with abundant oxygen vacancies. The hydroxyl groups on the surface of monolayer MXene attract cerium ions, which create surface defects in Ce-MOF and further promote the formation of oxygen vacancies. This results in a significant improvement in energy storage capacity, as well as performance in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The MXene@Ce-MOF composite exhibits a specific capacity of 496 F g−1, which is 1.8 times higher than that of pure Ce-MOF and 3.5 times higher than MXene alone. At a current density of 10 mA cm−2, the overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is as low as 270 and 220 mV, respectively, and the composite exhibits excellent cycling stability. Oxygen vacancy-based MOF composites play a crucial role in electrocatalysis and energy conversion.

Novel Ni-Doped Bismuth-Magnesium Tantalate Pyrochlores: Structural and Electrical Properties, Thermal Expansion, X-ray Photoelectron Spectroscopy, and Near-Edge X-ray Absorption Fine Structure Spectra.

The samples of Ni-doped bismuth magnesium tantalate pyrochlores with the general formula Bi1.4(Mg1–xNix)0.7Ta1.4O6.3 (x = 0.3, 0.5, 0.7) were obtained by solid-phase synthesis. The crystal structure of the pyrochlore type (sp. gr. Fd3̅m:2) was clarified by the Rietveld method on the basis of X-ray powder diffraction data. The unit cell parameters increase with the decreasing nickel content in the range from 10.5319(1) to 10.5391(1) Å. The electronic state of atoms is established by the XPS method. According to XPS analysis, bismuth atoms have an effective charge of +3, nickel atoms +(2 + δ), and tantalum ions +(5 – δ). The coefficient of thermal expansion of the lattice of the samples was calculated from high-temperature X-ray structural measurements in the range of −180 to 1050 °C. The average values of linear TECs α in the temperature ranges of 30–570 and 600–1050 °C are 5.1 × 10–6 and 8.1 × 10–6 °C–1, respectively. The monotonicity of the change in the thermal expansion coefficient in the temperature range from −100 to 1050 °C indicates the absence of phase transformations. All samples are dielectric and exhibit high activation energies ∼2.0 eV, moderately high dielectric constants ∼24–28, and tangent dielectric losses ∼0.002 at 1 MHz and 21 °C. The electrical properties of the samples are described by a simple parallel equivalent scheme. The chemical composition of the materials has little effect on the polarizability of the medium or on the value of the activation energy of the conductivity. Ionic processes in investigated materials at frequencies 200–106 Hz and at temperatures 100–450 °C were not detected.

Modulation of Weyl semimetal state in half-Heusler GdPtBi enabled by hydrostatic pressure

The excitation of Weyl semimetals obeys the relativistic Weyl equation and attracted significant research attention due to its unique electronic state. In this paper, we present an emerging approach for modulating the electron state of half-Heusler GdPtBi by hydrostatic pressure. Through measurements of the temperature-dependent resistivity and magnetoresistance (MR), a phase transition from a Weyl semimetal to a semiconductor state was identified at about 2.0 GPa upon increasing the hydrostatic pressure. Electron transport in semiconductive GdPtBi is found to be well describable by Mott variable-range-hopping. The simulated electronic structures under different hydrostatic pressures further indicate that changes in the electronic states of atoms in the primary unit cell result in a phase transition in GdPtBi. This work presents an effective strategy for modulating the electronic state by tuning the lattice constant.

Relationships between polypyrrole synthesis conditions, its morphology and electronic structure with supercapacitor properties measured in electrolytes with different ions and pH values

Despite a large number of articles about synthesis methods, structure, morphology and electrochemical properties of polypyrrole, none of these works reports the relationships between polypyrrole synthetic conditions, the electronic states of atoms in the polymer chains and its electrochemical properties in various electrolytes. Our work is dedicated to filling part of this gap. This work is focused on the effect of the synthetic medium used for polypyrrole synthesis on their atomic and electronic structure and morphology as well as investigation of the influence of these on the electrochemical characteristics of polypyrrole in aqueous electrolytes with different ions and pH values within a supercapacitor setup. It is shown that synthetic medium does not affect polymer particle shapes but changes particle sizes. Using oxygen functional groups containing synthetic medium based on water and ethanol leads to a decrease in C:N ratio, increase in C:O ratio, increase in the concentration of positively charged nitrogen-species and formation of linear-structured polymer chains. Contrary, acetonitrile-based synthetic medium without oxygen-containing functional groups leads to an increase in C:N ratio and concentration of neutrally charged nitrogen species, decrease in C:O ratio and formation of branched-structured polymer chains. Electrochemical properties of polypyrrole depend on the nature of the electrolyte, then nitrogen species and oxygen-containing functional groups in polypyrrole structure, and the size of polypyrrole particles. The favorable electrolyte for using polypyrrole in supercapacitors is neutral. The specific capacitance of polypyrrole produced in acetonitrile is shown to reach the value of ~ 385 F g −1 which is stable for more than 10,000 cycles in 1M KCl aqueous solution.

Bonding to a quantum corral

Surface Chemistry Chemical bonds generally form between electronic states of atoms; in principle, other electronic states could also form bonds. Stilp et al. found that the electronic states created within quantum corrals, large rings of iron atoms on a copper surface, can form chemical bonds with metal atoms on an atomic force microscope tip. The corral states form from many electrons but have a large spatial extent compared with an atomic orbital. The covalent bond to a 48-atom corral state had an energy of just 5 millielectron volts. Science , abe2600, this issue p. [1196][1] [1]: /lookup/doi/10.1126/science.abe2600

An X-ray Photoelectron Spectroscopic Study of the Poly-N-vinylpyrrolidone Desorption from the Surface of a Granulated Carbon Sorbent

The surface of a carbon sorbent modified with poly-N-vinylpyrrolidone was studied by X-ray photoelectron spectroscopy (XPS). The modification involves polymerization of N-vinylpyrrolidone on the carbon sorbent surface to form poly-N-vinylpyrrolidone. The elemental composition of the carbon sorbent surface before and after modification was determined by XPS. The electronic state of atoms of the identified elements on the surface was evaluated. The contact of the modified carbon sorbent with normal saline simulating the biological medium leads to partial removal (desorption) of the polymer from the granulated sample.

Electronic excitation of atoms by positron impact using the scaling Born approach

We consider the efficacy of the scaling Born positron (SBP) approach, in calculating reliable integral cross sections (ICS) for positron impact excitation of electronic states in atoms. We will demonstrate, using specific examples as H, He, Hg, and Mg, that this relatively simple procedure can generate quite accurate ICS when compared with more sophisticated methods. In the absence of the experimental data, comparisons are made with analogous electron scattering.

原子の電子状態( 化学ここが知りたい : Q&A に基づいて)

原子の電子状態( 化学ここが知りたい : Q&A に基づいて)

Phonon and electronic properties of the LiCaAlF6 crystal: Experiment and ab initio calculations

We have studied the IR polarized reflection spectra of LiCaAlF6 crystal in the range of 50–2000 cm–1 and have obtained parameters of dipole phonons. In order to calculate the electronic and vibrational properties of the crystal, we have applied the density functional method with the basis sets of Gaussian functions and plane waves. We have shown that the structure of electronic bands has a direct energy gap. The projected densities of electronic states of atoms, the Born effective charges, and the Mulliken populations have been found to be consistent with the ionic–covalent character of cation–fluorine interatomic bonds. The dielectric properties in high and low-frequency limits have been calculated. We have examined the longitudinal–transverse splitting of dipole modes and have revealed a phonon with an inverted splitting. The theoretical IR reflection and Raman spectra have been found to agree well with experiment. Based on the analysis of the dispersion of phonons in the Brillouin zone, we have revealed an effect of the “quasi-doubling” of the crystal cell along the z axis due to the competing interactions of atoms with nearest and next neighbors. We have found that phonons with frequencies higher than 500 cm–1 are separated by an energy gap and have predominantly stretching character of vibrations.

Elementary Errors in Contemporary Theoretical Physics

The paper discusses two cases showing crucial effects of error correction. It proves that contrary to the common belief, the electronic state of atoms having more than one electron has a multiconfiguration structure and that the central field approximati...

Enhanced one-photon double ionization of atoms and molecules in an environment of different species.

The correlated nature of electronic states in atoms and molecules is manifested in the simultaneous emission of two electrons after absorption of a single photon close to the respective threshold. Numerous observations in atoms and small molecules demonstrate that the double ionization efficiency close to threshold is rather small. In this Letter we show that this efficiency can be dramatically enhanced in the environment. To be specific, we concentrate on the case where the species in question has one or several He atoms as neighbors. The enhancement is achieved by an indirect process, where a He atom of the environment absorbs a photon and the resulting He(+) cation is neutralized fast by a process known as electron transfer mediated decay, producing thereby doubly ionized species. The enhancement of the double ionization is demonstrated in detail for the example of the Mg · He cluster. We show that the double ionization cross section of Mg becomes 3 orders of magnitude larger than the respective cross section of the isolated Mg atom. The impact of more neighbors is discussed and the extension to other species and environments is addressed.

Variational Quantum Monte Carlo with Inclusion of Orbital Correlations

Variational quantum Monte Carlo (VMC) method applied to interacting electron systems has played a pivotal role for the studies of electronic states of atoms, molecules and condensed matters. First, the many-body wave functions optimized by the VMC method provide good guiding functions in more accurate, diffusion quantum Monte Carlo (DMC) calculations for identical systems. Second, the VMC calculations themselves can give a good upper bound for the exact ground-state energy of many-electron systems when an appropriate form for the variational wave function is employed. In addition to a conventional form for the variational wave function that is expressed by the product of the Jastrow factor and the single Slater determinant, recent investigations have found that the expression in terms of many Slater determinants can provide a very accurate description of electronic states, especially for intrinsically multi-reference systems, which corresponds to the configuration interaction (CI) expansion method in conventional quantum chemistry. Although the CI method needs an extremely large number of expansion coefficients as variational parameters, the number of parameters can be reduced efficiently by using an idea of (molecular) orbital pair correlations. The purpose of the present paper is to examine the feasibility and usefulness of this idea within the framework of VMC method with the Jastrow–Slater wave function, where the ground state of a water molecule is investigated as a test case. In this study we rely on a variational wave function composed of a product of the Jastrow and Slater parts as 1⁄4 J S; ð1Þ

Zeeman splitting of photonic angular momentum states in a gyromagnetic cylinder

We show that, under the presence of a static magnetic field, the photon eigenfrequencies of a circular gyromagnetic cylinder experience a splitting that is proportional to the angular momentum density of light at the cylinder surface. Such a splitting of the photonic states is similar to the Zeeman splitting of electronic states in atoms. This leads to some unusual decoupling properties of these nondegenerate photonic angular momentum states, which are demonstrated through numerical simulations.

Chaotic ionization of a Rydberg atom subjected to alternating kicks: Role of phase-space turnstiles

We study the ionization of a highly excited Rydberg atom subjected to a periodic sequence of external electric-field pulses. Such systems are important laboratory and theoretical models of classical and quantum chaos. Furthermore, a good theoretical understanding of this chaos is important for controlling electronic states in atoms, as has been demonstrated in a series of recent experiments on the creation and control of electronic wave packets. Here, we present a theoretical analysis of the chaotic ionization of a hydrogen atom subjected to alternating positive and negative impulses. This analysis is based on the observation that the ionization of the atom is due to a turnstile in phase space which promotes the electronic state from negative to positive energy. The geometry of the lobes associated with the turnstile provides a clear picture of how the ionization process proceeds. Using this geometric intuition, we propose two experimental protocols to directly reveal the importance of the turnstile lobes in the laboratory.

Electronic energy exchange in high-temperature air

Kinetic processes with the participation of electronic states of atoms and molecules in air behind the shock wave front were analyzed. All metastable levels of molecular and atomic oxygen and nitrogen and nitrogen oxide molecules situated below the dissociation energy were analyzed. In high-temperature air, atom and molecule electronic states are formed in dissociation and recombination, electronic energy exchange in collisions of particles, and chemical exchange reactions. The formation of excited electronic states in the recombination of atoms and isoenergy vibrational energy transfer from highly excited vibrational levels into electronic energy is the fastest process. The quenching of metastable particles occurs in collisions between particles, dissociation and recombination, and chemical exchange reactions. A database on electronic energy exchange rate constants in high-temperature air is presented.

Gas-sensing properties of nanocomplex metal oxide

Abstract The development of CuO/Cd2 nanocomposites as the sensing material of semiconductor gas sensors is reported. CuO/C2 nanocomplex oxide is prepared by modified sol-gel method that uses copper nitrate, cerium nitrate and ethylene glycol as precursors. The optimized synthesis parameters and processing condition have been established. The particle size and distribution, phase morphology, specific surface, electronic states of atoms and gas sensing properties have been systematically characterized by Transmission Electron Microscope (TEM), Brunauer Emmett Teller (BET), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and gas sensitivity measurement. The results show that the sensor sensitivity depends on particle size, Cu/Ce cation ratio and calcination temperature. The effects of calcinations temperature and CuO loading on the gas sensitivity are also examined. The optimum calcination temperature and the CuO content for the highest sensitivity are 600°C and 12%, respectively. The combina...

On mechanisms of intensifying combustion due to the simultaneous excitation of vibrational and electronic states of reacting molecules

Excitation of the vibrational and electronic states ofatoms and molecules increases their reaction capacity[1–4]. This effect is attributed to a decrease in the bar-rier of endoergic reactions and an increase in the inter-action cross section for processes involving excitedmolecules. It has been shown that excitation of themolecular vibrations in H

Universal quantum cloning in cavity QED

We propose an implementation of an universal quantum cloning machine [UQCM, V. Buzek and M. Hillery, Phys. Rev. A 54, 1844 (1996)] in a cavity quantum electrodynamics experiment. This UQCM acts on the electronic states of atoms that interact with the electromagnetic field of a high-$Q$ cavity. We discuss here the specific case of the $\stackrel{\ensuremath{\rightarrow}}{1}2$ cloning process using either a one- or a two-cavity configuration.