Total Number Of Electrons Research Articles

A first-principles study of oxygen vacancy induced changes in structural, electronic and magnetic properties of La2/3Sr1/3MnO3

We have systematically assessed the influence of oxygen vacancy defects on the structural, electronic and magnetic properties of La2/3Sr1/3MnO3 via first-principles calculations using the bare GGA as well as the GGA + U formalism. The on-site Coulombic repulsion parameter U for Mn 3d orbital in the latter has been determined by the linear response theory. It is revealed that the introduction of the vacancy defects causes prominent structural changes in the microenvironment of a defect including the distortions of MnO6 octahedra. In contrast to the general notion, the GGA + U formalism is found to yield significantly more prominent structural changes than the bare GGA method. The octahedral distortion leads to a strengthening or weakening of the hybridization between Mn 3d and O 2p orbitals depending upon an increase or decrease, respectively, in the Mn–O distances as compared to the pristine system. The magnetic moments of the Mn atoms located in three typical sites of the vacancy-containing supercell are all larger than those in the pristine system. This enhancement for the Mn atoms located in the first- and third-nearest neighboring MnO6 octahedra of the vacancy defect originates from the electron transfer from 4s/3p to 3d orbitals. On the other hand, for the Mn atom located in the first-nearest neighboring site of the vacancy it is attributed to the increased total number of electrons in 3d orbitals due to the absence of one Mn–O bond. Furthermore, we have characterized the O-vacancy defect as a hole-type defect that forms a negative charge center, attracting electrons.

Measurement of the angle, temperature and flux of fast electrons emitted from intense laser–solid interactions

High-intensity laser–solid interactions generate relativistic electrons, as well as high-energy (multi-MeV) ions and x-rays. The directionality, spectra and total number of electrons that escape a target-foil is dependent on the absorption, transport and rear-side sheath conditions. Measuring the electrons escaping the target will aid in improving our understanding of these absorption processes and the rear-surface sheath fields that retard the escaping electrons and accelerate ions via the target normal sheath acceleration (TNSA) mechanism. A comprehensive Geant4 study was performed to help analyse measurements made with a wrap-around diagnostic that surrounds the target and uses differential filtering with a FUJI-film image plate detector. The contribution of secondary sources such as x-rays and protons to the measured signal have been taken into account to aid in the retrieval of the electron signal. Angular and spectral data from a high-intensity laser–solid interaction are presented and accompanied by simulations. The total number of emitted electrons has been measured as $2.6\times 10^{13}$ with an estimated total energy of $12\pm 1~\text{J}$ from a $100~{\rm\mu}\text{m}$ Cu target with 140 J of incident laser energy during a $4\times 10^{20}~\text{W}~\text{cm}^{-2}$ interaction.

Orbital angular momentum in a nonchiral topological superconductor

We investigate the bulk orbital angular momentum in a two-dimensional time-reversal broken topological superconductor with the Rashba spin-orbit interaction, the Zeeman interaction, and the $s$-wave pairing potential. Prior to the topological phase transition, we find the crossover from $s$ wave to $p$ wave. For the large spin-orbit interaction, even in the topological phase, $L_z/N$ does not reach $-1/2$, which is the intrinsic value in chiral $p$-wave superconductors. Here $L_z$ and $N$ are the bulk orbital angular momentum and the total number of electrons at zero temperature, respectively. Finally, we discuss the effects of nonmagnetic impurities.

Half-Metallic Properties in the New Ti2NiB Heusler Alloy

The electronic structure and magnetic properties of the new Ti2NiB Heusler alloy, which has a high-ordered CuHg2Ti structure, were examined using the self-consistent full-potential linearised augmented plane wave method within density functional theory. Analysis of the electronic band structures and state densities of the Ti2NiB full-Heusler compound revealed that whereas the spin-up electrons are metallic, the spin-down bands are characterised by a gap of 0.62 eV, resulting in stable half-metallic ferromagnetism with a magnetic moment of 3 μ B/f.u. The total magnetic moment (M t) and number of valence electrons (Z t) in the Ti2NiB compound were found to obey the Slater-Pauling (SP) rule of M t = Z t − 18. Due to their different surroundings, the magnetic moments of Ti (1) and Ti (2) exhibit distinct differences, with the magnetic contribution of Ti (1) slightly larger than that of Ti (2). A negative formation enthalpy value was also obtained, thus encouraging the experimental manufacture of the alloy. The band gap was elucidated to be mainly determined by the bonding and antibonding states created from the hybridisations of the d states between the Ti (1)-Ti (2) coupling and the Ni atom. Finally, the Ti2NiB compound was found to maintain 100 % polarisation at the Fermi level, with the half-metallic character present for lattice constants ranging from 5.60 to 6.50 A, thus making the alloy favourable for practical applications.

Theory of hysteresis during electron heating of electromagnetic wave scattering by self-organized dust structures in complex plasmas

Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.

Stability diagrams and turnstile operations of single-common-gate triple-dot single-electron devices with outer junction capacitances different from inner ones

Single-common-gate triple-dot single-electron devices with outer and inner junction capacitances, Ca and Cb, respectively, have been investigated. By changing the Ca/Cb ratio, the stability regions and overlap regions between neighboring stability regions change their shapes and then the sequences of single-electron transfers around the overlap regions also change. The most interesting phenomenon is that the arrangement of the stability regions along the gate voltage axis, which normally follows the total excess electron number in the three islands, is partially inverted. That is, the electron configuration in the three islands with the smaller total excess electron number is stable with a higher gate voltage range. Even when in such a situation, the turnstile operation is still possible though the sequence of single-electron transfer changes. The inversion of the arrangement can be explained in terms of the charging energies.

The half-metallicity of LiMgPdSn-type quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In): A first-principle study

Based on the first-principles calculations, quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In) including its phase stability, band gap, the electronic structures and magnetic properties has been studied systematically. We have found that, in terms of the equilibrium lattice constants, FeMnScZ (Z=Al, Ga, In) are half-metallic ferrimagnets, which can sustain the high spin polarization under a very large amount of lattice distortions. The half-metallic band gap in FeMnScZ (Z=Al, Ga, In) alloys originates from the t1u-t2g splitting instead of the eu-t1u splitting. The total magnetic moments are 3μB per unit cell for FeMnScZ (Z=Al, Ga, In) alloys following the Slater–Pauling rule with the total number of valence electrons minus 18 rather than 24. According to the study, the conclusion can be drawn that all of these compounds which have a negative formation energy are possible to be synthesized experimentally.

Electronic structures, magnetic properties and half-metallicity in Heusler alloys Zr2CoZ (Z=Al, Ga, In, Sn)

The electronic structures, magnetic properties, and half-metallicity of full-Heusler alloys Zr2CoZ (Z=Al, Ga, In, Sn) with the Hg2CuTi-type structure have been studied by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation (GGA). The Zr2CoZ (Z=Al, Ga, In, Sn) are found to be half-metallic ferrimagnets within a certain range of the lattice constant. The total magnetic moments (μt) of the Zr2CoZ alloys are calculated to be 2 for Z=Al, Ga, In and 3 for Z=Sn, linearly scaled with the total number of valence electrons (Zt) by μt=Zt−18. The origin of the band gap for these half-metallic alloys is well understood. These new Zr-based Heusler alloys are the ideal candidates for spintronic devices.

Critical opalescence and the true dielectric state in a Coulomb system

To study the critical opalescence effect in a two-component Coulomb system consisting of single-type electrons and nuclei, we consider the limit relations for static structure factors and analyze the singularities of the dielectric permittivity. We show that the critical opalescence effect can be observed not only at the critical point corresponding to the gas-liquid phase transition but also near the true dielectric state with zero static conductivity. With the available experimental data taken into account, we assume that the true dielectric state is the limit state of the liquid-liquid phase transition accompanied by sharp variations in the electrical conduction of the substances. We find that if the thermodynamic parameters correspond to the true dielectric state, then the critical opalescence effect can arise in the case where the squared fluctuation in the total number of electrons and nuclei in a two-component Coulomb system becomes infinite, as this occurs at the critical point corresponding to the gas-liquid phase transition.

Phase stability, band gap, and electronic and magnetic properties of quaternary heusler alloys FeMnScZ (Z = Al, Ga, In)

By using the first-principles calculations, we have systematically investigated the phase stability, band gap, and electronic structures and magnetic properties of quaternary Heusler alloys FeMnScZ (Z = Al, Ga, In). We found that FeMnScZ (Z = Al, Ga, In) alloys are half-metallic ferrimagnets at their equilibrium lattice constants and retain a high spin polarization over a quite wide range of lattice distortions. The half-metallic band gap in the FeMnScZ (Z = Al, Ga, In) alloys arises from t 1u-t 2g splitting but not e u-t 1u splitting. The total magnetic moments are 3 µB per unit cell for FeMnScZ (Z = Al, Ga, In) alloys, following the Slater-Pauling rule with the total number of valence electrons minus 18 rather than 24. Moreover, all of these alloys have a negative formation energy, which implies that they can be synthesized experimentally.

Correlation of martensitic transformation temperatures of Ni- Mn-Ga/Al-X alloys to non-bonding electron concentration

The martensitic transformation TM of the alloys of Ni-Mn-Ga and Ni-Mn-Al show a general trend of increase with electron per atom ratio (e/a) calculated from the total number of electrons outside the rare gas shell of the atoms. However prediction of TM fails among iron substituted Ni-Mn-Ga alloys and those with In doped for Ga, due to the absence of a useful trend. A scheme of computing modified electron concentration is presented considering only the non-bonding electrons per atom Ne/a of the compounds, based on Pauling's ideas on the electronic structure of metallic elements. Systematic variation of TM with Ne/a is reproduced for a large number of alloys of Ni-Mn-Ga and the anomaly observed for Fe containing alloys with e/a disappears. The non-bonding electron concentration is thus demonstrated to be effective in predicting TM of shape memory alloys of Ni-Mn-Ga-X system including the isoelectronic compounds of Ni-Mn-Ga-In.

Effects of Zn additions to highly magnetoelastic FeGa alloys

Fe1−xMx (M = Ga, Ge, Si, Al, Mo and x ∼ 0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at. % Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, −b1, comparable to those of the binary Fe-Ga alloy.

Coherent scattering of electromagnetic waves by self-organized dust structures: Degree of coherence

It is demonstrated explicitly that the scattering of electromagnetic waves by dust structures can be strongly enhanced as compared to incoherent scattering by random electrons. If the size of the dust structure is much less than the wavelength of the incident radiation, the scattering is coherent. In this case, the scattering is proportional to the square of the total number of electrons in the structure. In the opposite limit, the scattering is incoherent being proportional to the total number of electrons in the structure. The factor describing the degree of coherency is calculated numerically for several models of self-organized structures. It is demonstrated in general way that for sudden heating of electrons, the factor of coherency in scattering by structures can decrease by several orders of magnitude with subsequent increase after the heating is switched off. In laboratory dusty plasmas, the coherent scattering is proposed for diagnostics of universal structuring instability and as a probe for determining the properties typical for self-organized nature of structures that are observed in recent experiments.

Dynamical Local Lattice Instability Triggered High TcSuperconductivity

High Tc cuprate superconductors are characterized by two robust features: their strong electronic correlations and their intrinsic dynamical local lattice instabilities. Focusing on exclusively that latter, we picture their parent state in form of a quantum vacuum representing an electronic magma in which bound diamagnetic spin-singlet pairs pop in and out of existence in a Fermi sea of itinerant electrons. The mechanism behind that resides in the structural incompatibility of two stereo-chemical con gurations CuO4 and Cu O4 which compose the CuO2 planes. It leads to spontaneously uctuating Cu O Cu valence bonds which establish a local Feshbach resonance exchange coupling between bound and unbound electron pairs. The coupling, being the only free parameter in this scenario, the hole doping of the parent state is monitored by varying the total number of unpaired and paired electrons, in chemical equilibrium with each other. Upon lowering the temperature to below a certain T ∗, bound and unbound electron pairs lock together in a local quantum superposition, generating transient localized bound electron pairs and a concomitant opening of a pseudo-gap in the single-particle density of states. At low temperature, this pseudo-gap state transits via a rst order hole doping induced phase transition into a superconducting state in which the localized transient bound electron pairs get spatially phase correlated. The mechanism driving that transition is a phase separation between two phases having di erent relative densities of bound and unbound electron pairs, which is reminiscent of the physics of He He mixtures.

Simulation study on the correlation between the ground cosmic rays and the near earth thunderstorms electric field at Yangbajing (Tibet China)

Coincident study on the intensity change of the ground cosmic rays during thunderstorms is very important for understanding the acceleration mechanism of secondary charged particles caused by atmospheric electric field. It is found that the strength of the near earth thunderstorm electric field can be up to 1000 V/cm or even higher from ARGO-YBJ (where YBJ stands for Yangbajing, 4300 m a.s.l., Tibet, China) data in 2012. In this paper, Monte Carlo simulations are performed by using CORSIKA program to study the correlations between the intensity of the ground cosmic rays and the near earth thunderstorm electric field at YBJ. When the atmospheric electric field strength is higher than the threshold field strength (ERB) for the development of a runaway breakdown process, the total number of electrons and positrons is exponentially increases. At an electric field strength of 1500 V/cm, the number increases exponentially and reaches a maximum value at an atmospheric depth of ～520 g/cm2, where the electric field is slightly stronger than the threshold field strength. These results are consistent with the theoretical results of relativistic runaway electron avalanche (RREA) which was proposed by Gurevich et al. (Gurevich A V, Milikh G M, Roussel-Dupre R 1992 Phys. Lett. A 165 463) and also supports Dwyer's theory. The total number of electrons and positrons increases with the strength of the field in the negative field or in the positive field greater than 600 V/cm, while a certain degree of decline occurs in the positive field less than 400 V/cm. In the range 400-600 V/cm, the energy of the primary proton should be taken into account. For the primary energy that is lower than 80 GeV, the total number of electrons and positrons increases. And it does not change obviously when the energy is between 80 GeV and 120 GeV. For the primary energy exceeds 120 GeV, the number drops off, and the decrease is of ～4%. During thunderstorms, a short duration occurs in which the single particle counting rate increases as energy lowers, while a decrease happens with energy becoming higher than that from ARGO-YBJ data. Our preliminary results can give reasonable explanations to the experimental observations of ARGO-YBJ.

Correlation between carrier concentration distribution, I-V and C-V characteristics of a-InGaZnO TFTs

In this work, a technology computer-aided design (TCAD) device model based on an fabricated amorphous InGaZnO thin-film transistor (a-IGZO TFT) was established to study the correlation between carrier concentration distribution, current-voltage (I-V) and capacitance-voltage (C-V) characteristics of a-IGZO TFTs. The equilibrium carrier concentration of the a-IGZO layer influenced by defect states, interface fixed charges, gate and S/D electrodes were studied systematically and quantitatively. The a-IGZO thickness was varied from 10 nm to 140 nm. The doping concentration in the bulk a-IGZO layer and source/drain (S/D) contact regions were changed from 10 10 cm -3 to 10 20 cm -3 . The physical mechanisms underlying the I-V and C-V variation caused by above-mentioned parameters were explored by analyzing the energy band diagram and carrier concentration distribution in the a-IGZO layer. The total number of electrons in the channel region of the TFT was calculated by numeric integration for further investigation of its correlation with the a-IGZO thickness, I-V, and C-V characteristics of the a-IGZO TFTs.

Rényi Entropy, Tsallis Entropy and Onicescu Information Energy in Density Functional Reactivity Theory

Density functional theory dictates that the electron density determines everything in a molecular system's ground state, including its structure and reactivity properties. However, little is known about how to use density functionals to predict molecular reactivity. Density functional reactivity theory is an effort to fill this gap: it is a theoretical and conceptual framework through which electron-related functionals can be used to accurately predict structure and reactivity. Such density functionals include quantities from the information-theoretic approach, such as Shannon entropy and Fisher information, which have shown great potential as reactivity descriptors. In this work, we introduce three closely related quantities: Renyi entropy, Tsallis entropy, and Onicescu information energy. We evaluated these quantities for a number of neutral atoms and molecules, revealing their scaling properties with respect to electronic energy and the total number of electrons. In addition, using the example of second-order Onicescu information energy, we examined how its patterns change with the angle of dihedral rotation of an ethane molecule at both the molecular level and atoms-in-molecules level. Using these quantities as additional reactivity descriptors, researchers can more accurately predict the structure and reactivity of molecular systems.

Numerical simulation research of plasma characteristics in a multi-cusp proton source based on magnets layout

It is significant to study negative hydrogen ion source for the construction of Chinese national spallation neutron source (CSNS) and the implementation of the international thermonuclear experimental reactor (ITER) project. Numerical simulation is an indispensable research measure due to the physical characteristics of ion source. In view of the facts above, in this paper we first elaborate the self-developed three-dimensional particle-in-cell/Monte Carlo collisions (PIC/MCC) algorithm and then describe the mechanism of negative hydrogen ion (H-) volume production. Based on these, the multi-cusp proton source of the Chinese atomic energy research center is systematically simulated. In the cases of the same polarities and the opposite polarities of extraction magnetic fields, multi-cusp proton source discharge characteristics are discussed and analyzed respectively. The result shows that in the case of the opposite polarities of the two extraction magnets, magnetic drift directions near the two extraction magnets are the same and have great values, namely intense magnetic drift, which causes the total number of electrons to be big, and induces the high-energy electrons to become active in a specific area. And so, the volume production rate of H- ions is higher, that is to say, H- ions present Y drift. On the contrary, in the case of the same polarities of the two extraction magnets, the binding effect of electron is worse and the volume production rate of H- ions is lower, but spatial distribution of volume production H- is uniform.

Theoretical and experimental investigation of plasma antenna characteristics on the basis of gaseous collisionality and electron density

This paper reports plasma antenna characteristics investigated theoretically and experimentally, on the basis of the plasma parameters: gaseous collisionality and electron density. The antenna structure is a basic quarter-wavelength monopole antenna in the UHF band. The dependence of the antenna gain on the plasma parameters is obtained by analytical equations from plasma and antenna theory, and by numerical simulations. In the plasma antenna, the ratio of the electron elastic collision frequency to the total number of electrons at the plasma cross section determines the antenna’s internal loss and the electrical equivalent antenna length, whereas the ratio of the radio wave frequency to the total number of electrons at the plasma cross section determines the antenna’s resonant frequency. These results are confirmed by experimental results of the antenna’s impedance and radiation patterns.

Piezoelectrically-induced trap-depth reduction model of elastico-mechanoluminescent materials

Considering the detrapping of charge carriers due to reduction in trap-depth caused by piezoelectric field produced by applied pressure, an expression is derived for the detrapping rate of electrons. Then, an expression is obtained for the rate of generation of excited ions produced during capture of detrapped electrons by Eu3+ ions in persistent luminescent materials or by the energy released during electron-hole recombination in ZnS:Mn crystals. Finally, an expression is explored for the elastico-mechanoluminescence (EML) intensity, which is able to explain satisfactorily the characteristics of EML for the application of static pressure as well as for impact pressure. The total number of detrapped electrons and the total EML intensity are found to increase linearly with the electrostatic energy of the crystals in piezoelectric field. It is shown that the EML intensity should increase with the EML efficiency, number of crystallites (volume of sample), concentration of local piezoelectric regions in crystallites, piezoelectric constant of local piezoelectric regions, average length of the local piezoelectric regions, total number of electron traps, pressing rate, and applied pressure, and it should be higher for the materials having low value of threshold pressure and low value of trap-depth in unstressed condition. On the basis of the piezoelectrically-induced trap-depth reduction model of EML reported in the present investigation novel intense elastico mechanoluminescent materials having repetitive EML with undiminished intensity for successive loadings can be tailored which may find applications in sensing, imaging, lighting, colored displays, and other mechano-optical devices.