Average Number Of Electrons Research Articles

Structural, Thermal and Magnetic Characterization of Ni-Mn-Ga Ferromagnetic Shape Memory Alloys

Ni-Mn-Ga Ferromagnetic Shape Memory Alloys (FSMA) are highly interested in industrial actuators and energy harvesters because of its uniqueness in microstructure and multiple phases of these materials at different temperatures. The type of crystal structure, lattice parameters and magnetic properties depend on the alloy composition. The transformation and crystallographic properties are usually mapped to average number of valence electrons per atom. The present work deals with the fundamental characterization of single crystal and polycrystalline nature of these alloys. Though, the polycrystal shows low magnetic field induced stain (MFIS), the easy preparation techniques and cost effective aspects compared with the single crystals makes an impressive interest in dealing with that. The structural, thermal and magnetic parameters are observed and compared for these single and polycrystals.

Experimental Results in DBD Plasma Actuators for Air Flow Control

In this paper, several planar dielectric barrier discharge fluid-dynamics actuators have been experimentally investigated. The actuator is made by an electrode pair separated by a dielectric. It is characterized by a planar geometry, and it induces a volume force on the gas above it which modifies the fluid dynamics within the aerodynamic boundary layer. Several actuator geometries, dielectric materials, ac supply voltages, and supply frequencies have been used. Rotational and vibrational temperatures have been determined by means of spectroscopic measurements. Vibrational temperatures have been found to be one order of magnitude higher than the rotational ones, confirming the nonthermal behavior of the discharge. The translational temperature has been evaluated by thermographic observations of the dielectric surface heated by the plasma. The values of the translational temperature are in a very good agreement with those of the rotational temperature. Electric measurements have been carried out to determine the average power delivered to the discharge and to estimate the average electron number density. In the plasma induced by the discharge above the actuator, an average electron density of has been determined. The gas speed of the induced wall jet has been measured with a Pitot tube. The average power delivered to the electrodes increases with a power law of the applied voltage and linearly with the supply frequency. The induced speed increases with the increase of the average power until a plateau is reached. The efficiencies of the different actuators have been compared by evaluating the relation between average power and induced gas speed.

Superconductivity and Hybridization in the Fermion System at Zero Temperature

Some ground state properties of a fermion system are investigated. An initial Hamiltonian being a generalization of the lattice Anderson model describes this system as a two-band electron-phonon one where both of electron bands are narrow (one is wider than the other). Two bands are hybridized and electrons from both of them are strongly coupled to the same local phonons. After performing the Lang–Firsov type transformation, a new polaron Hamiltonian is obtained. As a result, there appear three effective polaron-polaron interactions in this Hamiltonian and the bandwidths of both of electron bands are reduced. It is assumed that the reduction of the bandwidth of one of the bands is sufficiently strong to make this band dispersionless. Each of the interactions can lead to superconductivity on its own but only one of them is taken into account at this stage; it is the interaction between electrons from the band with a dispersion. The Bogolyubov’s mean field approach is used in order to find the spectrum of the reduced effective Hamiltonian. The effect of the hybridization on the superconducting gap and the relationship between the critical hybridization and the average number of electrons from the wider band per lattice site are investigated.

A numerical approach for analyzing quantum dot infrared photodetectors' parameters

Quantum dot infrared photodetectors (QDIPs) have many advantages over other types of semiconductor-based photodetectors. However some of its characteristics have been investigated theoretically, there are many unstudied points. In this paper a new approach is presented to evaluate quantum dot infrared photodetectors dark current and photocurrent. In this study, it is assumed that both thermionic emission and field-assisted tunneling mechanisms determine the dark current of quantum dot detectors. Based on these assumptions, new formula for average number of electron in a quantum dot for both, dark and illumination condition is calculated, which is more accurate than the previous reported formulas; because in deriving previous reported formulas, it was assumed only thermionic emission determines dark current but field-assisted tunneling mechanisms has not been considered. Then numerical method is used to calculate the average number of electron in a quantum dot and to determine dark current and photocurrent. The theoretical results are compared with experimental data. They have good agreement with available experimental data.

A new approach for modeling of dark current characteristics of quantum wire infrared photodetectors

In order to study the dark current characteristics in a quantum wire infrared photodetector (QRIP), the average number of electrons in quantum wires (QRs) must be got, which is mostly too complicated. In this paper we give a simple formula to calculate the average number of carriers in a quantum wire (QR) that can be easily evaluated by mathematical softwares, and then we use this formula to study dark current characteristics of a quantum wire infrared photodetector (QRIP).

Investigation of the quantum dot infrared photodetectors dark current

Quantum dot infrared photodetectors (QDIPs) are more efficient than other types of semiconductor based photodetectors; so it has become an actively developed field of research. In this paper quantum dot infrared photodetector dark current is evaluated theoretically. This evaluation is based on the model that was developed by Ryzhii et al. Here it is assumed that both thermionic emission and field-assisted tunneling mechanisms determine the dark current of QDIPs; moreover we have considered Richardson effect, which has not been taken into account in previous research. Then a new formula for estimating average number of electrons in a quantum dot infrared photodetector is derived. Considering the Richardson effect and field-assisted tunneling mechanisms in the dark current improves the accuracy of algorithm and causes the theoretical data to fit better in the experiment. The QDIPs dark current temperature and biasing voltage dependency, contribution of thermionic emission and field-assisted tunneling at various temperatures and biasing voltage in the QDIPs dark current are investigated. Moreover, the other parameter effects like quantum dot (QD) density and QD size effect on the QDIPs dark current are investigated.

Absolute cross sections for projectile electron loss accompanied by target multiple ionization in collisions of He+ with noble gases

Absolute cross sections for projectile electron loss accompanied by target multiple ionization in collisions between He+ ions and noble gases have been measured for energies between 1.0 and 3.5 MeV. The data have been compared with other absolute cross sections that exist in the literature for the same projectile, and with calculations for the screening mode (nucleus–electron interaction) using both perturbative (plane-wave Born approximation (PWBA)) and non-perturbative (extended classical-impulse free-collision model, sudden approximation and coupled-channel method) approaches, and for the antiscreening mode (electron–electron interaction) within the PWBA. The energy dependence of the average number of active electrons for the antiscreening has been described by means of a simple function, which is ‘universal’ for noble gases but projectile dependent. A previously developed method has been employed to obtain the number of active electrons for each target subshell in the high-velocity regime.

Quantitative Microplasma Electron Number Density Measurement by Coherent Microwave Rayleigh Scattering

In this paper, a method for quantitative measurement of electron number density in a microplasma by coherent microwave Rayleigh scattering is described. Coherent microwave Rayleigh scattering reaches its maximum when the microwave frequency is at its resonance frequency. The resonance frequency depends on the electron number density in the microplasma and the electron-neutral and Coulomb collisional frequencies. When a subnanosecond microwave pulse illuminates the microplasma, the average electron number density can be measured from the frequency analysis of microwave scattering. The technique will be able to quantitatively measure subnanosecond-resolved electron number density evolution in the microplasma.

Entropic bond descriptors from separated output-reduced communication channels in atomic orbital resolution

Communication Theory of Chemical Bond (CTCB) in atomic orbital resolution is used to define entropic bond orders of diatomic molecular fragments. Partial communication channels for separated information flows from atomic centers and two alternative output-reducion schemes with their entropic descriptors are proposed. Also two types of information that can be transmitted through communication system are identified: information about molecular electron occupations and information about bonding shares of atomic orbitals. The former is used to evaluate an average number of electrons engaged in bond forming process while the latter provides information about electron localization in chemical bond. Calculated entropic bond orders and their IT-covalency and IT-ionicity components are in good agreement with both chemical intuition and MO theory predictions.

Absolute cross sections for electron loss, electron capture, and multiple ionization in collisions ofC3+with noble gases

Absolute charge-state-correlated cross sections for projectile electron loss, electron capture, and target multiple ionization in collisions between ${\mathrm{C}}^{3+}$ ions and noble gases have been measured for energies between $1.3$ and $3.5$ MeV. The data have been compared with other similar absolute cross sections existent in the literature for several projectiles. Calculations for the single-loss$\ensuremath{-}$multiple-ionization channel have been performed for the screening mode, using both an extended version of the classical-impulse free-collision model and the plane-wave Born approximation (PWBA), and for the antiscreening mode within the PWBA. The energy dependence of the average number of target active electrons which contribute to the antiscreening has been described by means of a simple function, which is ``universal'' for noble gases but, in principle, projectile dependent. A method has been developed to obtain the number of active target electrons for each subshell in the high-velocity regime, which presented physically reasonable results. Analyses of the dependences of the single-capture and transfer-ionization (SC and TI, respectively) processes on the projectile charge states showed that, for He, equally charged bare and dressed projectiles have very similar cross sections; the latter thus acting as structureless point charges. A behavior similar to that in the SC has been observed for the pure single ionization of He by projectiles with different charge states and of the other noble gases by singly charged projectiles. It has been shown that the ${q}^{2}$ dependence of the pure-single and total-ionization cross sections, predicted by first-order models, is only valid for high-collision velocities. For slower collisions, the electron capture process becomes more relevant and competes with the ionization channel, a feature which grows in importance as the projectile charge state increases.

Relation of structure and magnetic properties in nickel substituted MgFe 2O 4

This study presents the structure-related magnetic properties of nickel substituted MgFe 2− x Ni x O 4 with x=0.01–0.20, synthesized using thermal decomposition of metal organic starting materials. The samples were annealed at temperatures ranging from 900 to 1100 °C in air. Magnetic and electric properties were characterized using vibrating sample magnetometer and an impedance analyzer, respectively. The fraction of inverse spinel structure was found to decrease with increase in nickel concentration. The samples exhibited soft magnetic behavior. The magnetization was found to depend on the substitution of Ni atoms on the octahedral sites and on the average number of valence electrons. The dielectric properties were found to have higher values at low frequency and decreased with increase in frequency. An enhancement of the dielectric constant was observed upon increase in the annealing temperature.

Modulated structure of β-brass CuZn compressed to 90 GPa

Cu–Zn is a classic example of an alloy system displaying a sequence of phases along an alloy composition, called Hume-Rothery phases. The crystal structure of these phases is determined by valence electron concentration (that is the average number of valence electrons per atom), and the lowering of the electronic energy is considered the key factor for the structure stabilization. Using powder x-ray diffraction, we study the β-phase of an equiatomic CuZn alloy in its body-centered cubic (bcc) phase in the pressure range up to 90 GPa and find a transformation to a modulated trigonal structure at around 40 GPa. We analyze the structural distortion of bcc CuZn by looking at the configuration of the Brillouin zone of the bcc and the trigonal structures and their interaction with the Fermi surface. We demonstrate that the stabilization of the complex high-pressure structure can be explained with the Hume-Rothery effect.

Quantum limits to the electron field emission from tapered conductive sheets

A model has been constructed in order to study the effects of quantum confinement on the electron population on tapered conductive sheets. A two-dimensional rounded nanocone was considered for this study and the Schrödinger equation was solved analytically on the entire system. The average number of electrons on the tip region was shown to be strongly influenced by the geometrical parameters of the system, such as the tip and base radius and the overall length. Field emission from such structures was also investigated using a simple one-dimensional Wentzel–Kramers–Brillouin approximation. The limitations on the electron population imposed by the strong quantum confinement at the tip region will have important consequences on the field emission current obtained from these structures.

Saturation Magnetic Induction Prediction for Amorphous Magnetic Alloys by Using Support Vector Regression

This paper illustrates an application of support vector regression (SVR) approach in forecasting the saturation magnetic induction (Bs) of amorphous magnetic alloys. SVR was trained and tested with an experimental data set comprised of five input variables, comprising the average number of valence electrons of amorphous magnetic alloys, mixed entropy, ratio of radii, difference of electron density, and difference of work function. The prediction performance of SVR was compared with that of artificial neural networks’ (ANN) model. The results demonstrate that the prediction ability of SVR is superior to that of ANN. This investigation indicates that SVR-based modeling is a practically useful tool in prediction of the saturation magnetic induction of amorphous alloys. This study provides a novel methodology to foresee the saturation magnetic induction in sintering/development of novel amorphous magnetic alloys possessing high saturation magnetic induction.

N-dependence of electronic energies in atoms and molecules: Mulliken and exponential interpolations

The unphysical artifact of the Mulliken (parabolic) interpolation of the dependence of the electronic energy of atoms and molecules on the system average number of electrons N is identified. To remedy this shortcoming a smooth exponential interpolation between the energies of the neutral system, its cation and anion is suggested. The trends exhibited by the associated electronegativity and chemical hardness scales are examined.

Exact exchange-correlation potentials in spin-density functional theory and their discontinuities at unit electron number

The exact exchange-correlation potential of Kohn–Sham density functional theory is known to jump discontinuously by a spatial constant as the average electron number, N, crosses an integer in an open system of fluctuating electron number, with important physical consequences for charge transfers and band gaps. We have recently constructed an essentially exact exchange-correlation potential vxc for N electrons (0 ≤ N ≤ 2) in the presence of a –1/r external potential, i.e., for a ground ensemble of H+ ion, H atom, and H– ion densities. That construction illustrates the discontinuity at N = 1, where it equals IH – AH, the positive difference between the ionization energy and the electron affinity of the hydrogen atom. Here we construct the corresponding essentially exact spin-up and spin-down exchange-correlation potentials vxc,↑ and vxc,↓ of the Kohn–Sham spin-density functional theory, more commonly used for electronic structure calculations, for the ground ensemble with most-negative z-component of spin (or equivalently in the presence of a uniform magnetic field of infinitesimal strength). The potentials vxc, vxc,↑, and vxc,↓, which vanish as r → ∞ (except when N approaches an integer from above), are identical for 0 ≤ N ≤ 1 and for N = 2 but not for 1 < N < 2. We find that the majority or spin-down potential has a spatially constant discontinuity at N = 1 equal to IH – AH. The minority or spin-up potential has a discontinuity which is this constant in one order of limits, but is a spatially varying function in a different order of limits. This order-of-limits problem is a consequence of a special circumstance: the vanishing of the spin-up density at N = 1.

Average Numbers of Scintillation Photons and Electrons Produced by an Alpha Particle in High-Density Xenon Gas

The average numbers of scintillation photons and electrons produced by an α-particle with 5.49 MeV were determined in high-density xenon gas in the density range of 0.03–0.12 g/cm3. No significant density dependence was observed for the number of excited atoms or liberated electrons. The average energies expended per excited atom (Wex-value) and liberated electron (W-value) were found to be 34.1±2.4 and 20.9±0.4 eV, respectively. It was also found that some liberated electrons escape from recombination at zero electric field.

The fcc–bcc Bain path in In–Sn and related alloys at ambient and high pressure

Experimental high-pressure structural studies on an In–Sn alloy containing8 at.% Sn reveal an isostructural transition of a face-centered tetragonalphase at pressures above 15 GPa with a switch of the axial ratio fromc/a>1 toc/a<1. Such tetragonal phases in binary alloys based on In and Sn are analyzed inrelation to the Bain path, i.e. a transformation between a face-centered cubic(fcc) and a body-centered cubic (bcc) structure. Variation of the axial ratioc/a in these phases correlates with the average number of valence electrons per atom in analloy. A common Bain path from fcc to bcc is discussed within a nearly-free-electron modelof Brillouin-zone–Fermi-sphere interactions.

The structure, thermodynamic and electrochemical properties of hydrogen-storage alloys: An empirical methodology of average numbers of total electrons

It is just the best time to compile and compare the experimental data and to explore the possible laws and to discover the relation between the crystallographic parameters, thermodynamic and electrochemical properties, based on lot of the published experimental data about the hydrogen-storage alloys. An empirical correlation between the unit cell volume and the enthalpy change, equilibrium pressure, discharge capacity has been constructed. The violent change of the equilibrium pressure with the unit cell volume might indicate the change in the interaction nature between the host alloy atoms and the intercalated hydrogen atoms. The dependence of unit cell volume vs. average numbers of total electrons for AB 5-type alloys exhibits same change tendency as that of the Vanderwaals radius vs. atomic numbers from Fe to Se in the elements' periodic table. It is possible that the total numbers of the electrons decides the unit cell volume.

Insight into performance of quantum dot infrared photodetectors

In the paper, an algorithm for theoretical evaluation of dark and illumination characteristics of quantum dot infrared photodetectors (QDIPs) is presented. The developed algorithm is based on a model previously published by Ryzhii and co-workers. In our considerations it is assumed that both thermionic emission and field-assisted tunnelling mechanisms determine the dark current of quantum dot detectors. The model permits to calculate the dark current, current gain, average number of electrons in quantum dots, photocurrent, and detector responsivity as a function of the structural parameters. Moreover, it explains some features of QDIP characteristics. In several cases, the theoretical predictions are compared with experimental data. Good agreement between both kinds of data has been obtained.