Value Of Effective Charge Research Articles

Analytical estimate of effective charge and ground-state energies of two to five electron sequences up to atomic number 20 utilizing the variational method

BackgroundThe variational method, a quantum mechanical approach, estimates effective charge distributions and ground-state energy by minimizing the Hamiltonian's expectation value using trial wave functions with adjustable parameters. This method provides valuable insights into system behavior and is widely used in theoretical chemistry and physics. This paper aims to investigate ground-state energies and isoelectronic sequences using the variational method, introducing a novel approach for analyzing multi-electron systems. This technique allows for determining effective charge values and ground-state energies for 2–5 electrons sequence up to Z ≤ 20. Hydrogenic wave functions are used as a trial wave function to calculate effective charge in 1 s, 2 s, and 2p states. Two varying parameters were used to calculate an approximate wave function for the system. These values are then used in non-relativistic Hamiltonian with electron–electron interaction terms to calculate the ground-state energy of an atom.ResultThe results align with the reported experimental values, showing a marginal 1% error.ConclusionA Python algorithm is established based on the variational principle. It was found that, based on a few selected parameters in scripting the program, a very promising result was obtained. Furthermore, adding more variational parameters can minimize the difference between experimental and theoretical values, and this technique can be extended to elements with higher atomic numbers.

Regulating Zinc Deposition via Zincophilic 2D‐Cu2Te as the Current Collector to Suppress Dendrite Formation toward High Performance Aqueous Zinc‐Ion Batteries

AbstractIn this study, we synthesized standing 2D δ‐Cu2Te flakes (δ‐CTFs) via a facile post‐tellurization process, which served as the current collector to accommodate zinc (Zn) for AZIBs. These flakes exhibited low nucleation overpotential and low interfacial impedance, facilitating the plating/stripping of Zn ions. Interestingly, the hydrophilicity and standing structure of δ‐CTFs guided the electrodeposited Zn to laterally grow on the surface of δ‐CTFs, effectively suppressing Zn dendrite formation. The Zn@δ‐CTFs anode exhibited a long‐term cycling duration of 510 hours in a symmetric cell, which is far superior to previous reports. Even under high current density of 10 mA cm−2, the anode was able to perform stably with a cycle life of 110 hours. The machine learning model was exploited to predict the effective charge value, discovering that Zn migrated in Cu2Te were subject to the larger driving force of migration under applied field. Finally, the Zn@δ‐CTFs//MnO2 full battery exhibited excellent rate‐dependent capacity and maintained a capacity of 100 mAh g−1 after 1000 cycles at a current density of 1 A g−1, without Zn dendrite formation. This research provides a new strategy for regulating Zn deposition to address dendrite issues toward long lifespan AZIBs.

A theoretical study on the effective quadrupole deformations of 100−128Cd isotopic chain

In this paper, we have applied a simple interacting boson model (IBM) to Cadmium (Cd) isotopic chain to obtain the quadrupole transition rates and effective deformation. To this aim, we use the U(5) and O(6) dynamical symmetry limits of this model to classify the considered states. Also, the energy spectra of some levels are determined which their experimental counterparts are available. The results describe the regular states with high accuracy but suggest notable deviation in the prediction of intruder energy levels. Also, our results show the advantages of this formalism in the description of quadrupole transition rates and indicate a significant relationship between the values of effective quadrupole deformations and effective boson charge. Also, for the [Formula: see text]Cd, [Formula: see text]Cd and [Formula: see text]Cd isotopes, we have the largest variation of the quadrupole shape constants which are located in the region of shape coexistence. The study of the ratios of different energy levels indicates that there is a close relationship between ground and excited-state quantum phase transitions (ESQPTs).

Comparative studies of metal‐organic decomposed Ga x Ce y O z and CeO 2 based functional MOS capacitor

A comparison between metal-organic decomposed GaxCeyOz and CeO2 passivation layers subjected to post-deposition annealing at 800°C in oxygen ambient was presented. Mitigation in the formation of positively charged oxygen vacancies in GaxCeyOz layer was disclosed by the grazing incidence X-ray diffraction characterization as well as the acquisition of a lower value of positive effective oxide charge (Qeff) than CeO2 layer. In addition, GaxCeyOz layer was able to sustain a higher electric breakdown field and a lower leakage current density due to the attainment of a lower interface trap density extracted using Terman's and high-low methods, slow trap density, and Qeff when compared with CeO2 layer.

Importance of macroscopic polarization on vibrational properties and the robust nature of (001) surface states of SnTe

Here, we study the importance of macroscopic polarization for explaining the lattice dynamics of SnTe. Along with this, the robustness of (001) surface states is discussed for the practical application of this compound. The long range Coulomb forces using nonanalytical term correction are needed for proper explanation of experimental phonon modes with the Born effective charge's value of ∼5.5 (∼-5.5) for Sn (Te) atom. The peaks' positions of phonon density of states are in good agreement with the experimental observation. The Debye temperature for SnTe is found to be ∼189 K. We have also explored the possibility of protecting the (001) surface states via mirror and time-reversal symmetry. These surface states are expected to be robust against the point and line defects.

Relationship between dose and stopping power values for electrons in skin and muscle tissues.

Absorbed dose and stopping power of the target material are two important parameters for determining the radiation effects. In this work, the relationship between these two parameters has been investigated for electron beams incident on skin and muscle tissue. Absorbed dose was obtained by using the EGSnrc code and the stopping power values were calculated by considering the velocity-depended effective charge and mean excitation values. To obtain the relationship between absorbed dose and stopping power values, these parameters were graphed together and simple fitting functions have been obtained. The results obtained show that these parameters are linearly correlated with each other.

Turbulent impurity transport simulations in Wendelstein 7-X plasmas

A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried out with the recently developed gyrokinetic code stella. Different impurity species are considered in the presence of various types of background instabilities: ion temperature gradient (ITG), trapped electron mode (TEM) and electron temperature gradient (ETG) modes for the quasilinear part of the work; ITG and TEM for the nonlinear results. While the quasilinear approach allows one to draw qualitative conclusions about the sign or relative importance of the various contributions to the flux, the nonlinear simulations quantitatively determine the size of the turbulent flux and check the extent to which the quasilinear conclusions hold. Although the bulk of the nonlinear simulations are performed at trace impurity concentration, nonlinear simulations are also carried out at realistic effective charge values, in order to know to what degree the conclusions based on the simulations performed for trace impurities can be extrapolated to realistic impurity concentrations. The presented results conclude that the turbulent radial impurity transport in W7-X is mainly dominated by ordinary diffusion, which is close to that measured during the recent W7-X experimental campaigns. It is also confirmed that thermodiffusion adds a weak inward flux contribution and that, in the absence of impurity temperature and density gradients, ITG- and TEM-driven turbulence push the impurities inwards and outwards, respectively.

Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen-rich 5-aminotetrazole.

This article presents a thorough density functional theory based comparative study on nitrogen-rich 5-aminotetrazole alkali metal salts M 5-At (M = Li, K, Rb, Cs). The calculated structural parameters using plane-wave pseudopotential method are consistent with the experimental results. The computed vibrational frequencies at ambient pressure show that vibrational modes in high energy region are due the NH bond of NH2 group. Pressure variation IR spectra of these materials show clear frequency shifts where Li 5-At shows an overall red shift below 900 cm-1 contrary to the blue shift seen in other materials in this range. The born effective charge values reveal the presence of strong covalency between N, H, and C atoms whereas an increased ionic nature is seen as the atomic number of metal atoms increases. Furthermore, we used full potential linear augmented plane wave (FP-LAPW) method for calculating electronic structure and optical properties with TB-mBJ potential which provides an enhanced band gap for all materials compared to standard GGA functional. Electronic structure calculation reveals that all the compounds are indirect band gap insulators with the exception of Li 5-At. The computed partial density of states show mixed ionic-covalent nature in metal-N/C bonds and covalent nature in NC bonds. In addition, we are also presenting the optical properties such as real and imaginary dielectric constant, absorption, refraction, reflection, loss spectrum as functions of photon energy. From the optical properties we can conclude that all the studied compounds are optically anisotropic in nature and are good absorbers in the ultraviolet (UV) region.

19F Ex Situ Solid-State NMR Study on Structural Differences in Pores of Activated Carbon Series Derived from Chemical and Physical Activation Processes for EDLCs

This study demonstrates the differences in the capacitive behaviors between the pore structures generated by physical and chemical activation and infiltrated electrolyte ions in the pores. Three paired samples were successfully synthesized with similar specific surface areas and average pore widths through steam activation (physical) and KOH activation (chemical) processes. Their capacitive behaviors were investigated with their effective charge (β) values through 19F ex situ solid-state NMR and electrochemical methods. Despite their similar pore characteristics, their capacitive behaviors were totally different because of the differences in their surface structures such as the edge-rich for KOH activation and basal-rich for steam activation. The KOH-activated series displayed higher capacitances and β values than those of the steam-activated series due to the existence of an edge-rich surface structure, which induced more effective charging under electrochemical polarization. Additionally, the pore development model (domain theory) through the KOH and steam activation approaches was discussed by using the β values and chemical shifts by using this 19F ex situ solid-state NMR technique.

Study of lithium influx, radiation, transport and influence on plasma parameters in the T-10 tokamak

An investigation of lithium influx to plasma, radiation, transport, and its influence on plasma parameters is carried out using spectroscopy and transport modeling methods. The lithium source in the discharge of the T-10 tokamak is a moving Li-limiter based on a tungsten capillary-pore system (CPS). A strong dependence is found between the Li influx to plasma on the distance between the Li-limiter and plasma current boundary in the scrape-off layer (SOL) region. It is shown that if the Li-limiter is located on the radius of the chamber wall (r ≈ 40 cm), lithium influx to plasma is at a low level with a value ∼2·1018 s−1 and the Li nuclei concentration in the plasma does not exceed ∼0.5% of electron density ne with the effective charge value Zeff ≈ 1.2. If the Li-limiter is moved to the current radius (aL = 30 cm), lithium influx to plasma reaches ∼3 · 1020 s−1, which leads to a formation of lithium plasma with the density limit of (the Greenwald density limit) with a Zeff value of ≈2.9 and ≈10% of the remaining deuteron density. In this case, the lithium radiation losses power estimated in Li-plasma is extremely low and does not exceed ≈15% of ohmic power. All obtained results are interpreted using transport models. Changing the lithization level of the chamber walls can significantly reduce the level of C, O, and W impurities and greatly affect the Zeff values. The dependencies of energy confinement times in the electron and ion components on the value of the averaged electron density are investigated in regimes with significantly varying Zeff values. The paper presents the computational analysis of the lithium radiation power at the plasma periphery and in the SOL as a function of boundary conditions, transport characteristics, and confinement times of lithium ions.

TECXY simulations of multi‐species impurity seeding in DEMO reactor

Numerical studies have been performed to investigate the influence of the few impurity species on the heat load reduction and the SOL plasma parameters in the European DEMO reactor. Two‐dimensional multi‐fluid TECXY code has been used to model edge plasma transport described by the classical set of transport equations of multi‐species plasma derived by Braginskii. The TECXY code solves transport equations for few impurity species and all associated ionization stages simultaneously in a two‐dimensional poloidal geometry.This paper describes the results of numerical simulations of the edge plasma performed for the DEMO reactor with neon and krypton seeding, as well as with a mixture of neon and krypton impurities. We aimed to obtain the energy flux reduction to the target plate at the smallest possible increase of the effective charge value considering gas puffing with various mixtures of impurities. It has been found that the heat load reduction can be improved for a specific mixture of impurity species seeded simultaneously to the edge plasma.

Stability analysis of ELMs in long-pulse discharges with ELITE code on EAST tokamak

One challenge in long-pulse and high performance tokamak operation is to control the edge localized modes (ELMs) to reduce the transient heat load on plasma facing components. Minute-scale discharges in H-mode have been achieved repeatedly on Experimental Advanced Superconducting Tokamak (EAST) since the 2016 campaign and understanding the characteristics of the ELMs in these discharges can be helpful for effective ELM control in long-pulse discharges. The kinetic profile diagnostics recently developed on EAST make it possible to perform the pedestal stability analysis quantitatively. Pedestal stability calculation of a typical long-pulse discharge with ELITE code is presented. The ideal linear stability results show that the ELM is dominated by toroidal mode number n around 10–15 and the most unstable mode structure is mainly localized in the steep pressure gradient region, which is consistent with experimental results. Compared with a typical type-I ELM discharge with larger total plasma current (Ip = 600 kA), pedestal in the long-pulse H-mode discharge (Ip = 450 kA) is more stable in peeling-ballooning instability and its critical peak pressure gradient is evaluated to be 65% of the former. Two important features of EAST tokamak in the long-pulse discharge are presented by comparison with other tokamaks, including a wider pedestal correlated with the poloidal pedestal beta and a smaller inverse aspect ratio and their effects on the pedestal stability are discussed. The effects of uncertainties in measurements on the linear stability results are also analyzed, including the edge electron density profile position, the separatrix position and the line-averaged effective ion charge value.

Effect of inter-particle potential on the effective viscosity of nanofluids

A theoretical model of effective viscosity of nanofluids considering the effect of inter-particle potentials is developed by mathematical methods. Repulsive DLVO potential of charged particles are selected to express the inter-particle potential and a compact form of the effective viscosity of nanofluids is reached. The expression shows qualitatively that the long-range repulsion between particles can lead to the increase of the effective viscosity of nanofluids which could even exceed the effect brought by Brownian motion in certain circumstances. The model is validated by several experimental results from references. The effective viscosity data gained from experiments can be accurately predicted by careful assignment of the value of effective charge number. When the nanoparticle volume fraction is less than 0.5%, the corresponding number of the effective charge is of 103. When the nanoparticle volume fraction is around 1%, the proper value of effective charge is about 102. And when the nanoparticle volume fraction further increases to about 10%, the effective charge is to the order of 10. These results also reveal the change of particle agglomeration structure under different nanoparticles volume fractions. The model deducted in the current study proposed a reasonable way to explain the abnormal enhancement of the effective viscosity of nanofluids, which is a good complement to the present researches in the specific field.

On the Effect of Magnetic Fields on Electromigration Processes of Liquid Inclusions in Aluminum and Silicon

The substances move in conductors owing to drift of ions that occurs due to momentum exchange at collisions between the conductive carriers and atomic lattice. This effect is substantial at high-density direct currents, e.g., in power electronics. Therefore, the assigned subject matter is topical. The aim of this work is investigation of the effect of magnetic fields on electromigration processes of liquid inclusions in aluminum. We performed an analysis of formation and electromigration of molten Al-Si inclusions in silicon and aluminum crystals. It was found that molten inclusions 50-800 μm in size are formed in the studied system by contact melting in the 850-920 K temperature range. The electro-stimulated migration of inclusions along the electric lines of force at current densities j  4106 A/m2 was also established. From the dimensional dependence of specific velocity of travel w/j of molten Al-Si regions in silicon and aluminum, we made a conclusion concerning mechanisms of molten regions travelling. These are melting and crystallization at interphase boundaries due to thermoelectric phenomena and electromigration of atoms in the inclusion bulk. The numerical values of effective charges of Al and Si atoms in Al-Si melts as well as Peltier coefficients of the crystal-melt system were determined experimentally. It was found that preexposure of aluminum alloy (with iron concentration of ~0.6%) in a static magnetic field (В = 0.7 T) leads to changing of dimensional dependence of migration velocity of inclusions (i.e., it is magneto-sensing).

Coarse-Grained Antibody Models for "Weak" Protein-Protein Interactions from Low to High Concentrations.

So-called "weak" protein-protein interactions are important for the control of solution properties and stability at elevated protein concentrations (c2) but are not practical to capture in atomistic simulations. This report focuses on a series of coarse-grained models for predicting second osmotic virial coefficients (B22) and high-concentration Rayleigh scattering (osmotic compressibility) as a function of c2 for monoclonal antibodies (MAbs) that are of interest in biotechnology. B22 and molecular volume along with c2-dependent osmotic compressibility were calculated for a series of models with increasing structural detail. Models were refined to include contributions from sterics, short-ranged van der Waals and hydrophobic attractions, screened electrostatics, and the flexibility of the mAb hinge region. The results highlight shortcomings for spherical models of MAbs and a useful balance between numerical accuracy and computational burden offered by models based on 6 or 12 spherical, partly overlapping domains. The results provide bounds for realistic values of effective charges on variable domains in order for MAbs to be stable in solution and more generally illustrate semiquantitative bounds for the space of model parameters that can reproduce experimental behavior and provide a basis for future development of computationally efficient and accurate CG mAb models to predict both low- and high-c2 behavior.

Revisiting Benzylidenequinolinylnickel Catalysts through the Electronic Effects on Catalytic Activity by DFT Studies

The reaction activities for a series of benzylidenequinolin nickel complex systems are studied by density functional theory methods. The effective net charge values obtained on nickel atoms illustrate the correlation with experimental activities. Catalytic activity increases with the higher effective net charge values. The energy gaps (epsilon(1)) between Ni complex's lowest unoccupied molecular orbita (LUMO) and ethylene's highest occupied molecular orbital (HOMO) orbitals are calculated, regarding both pre-catalysts and active species. The results show that there are also relationships between epsilon(1) and catalytic activities. Comparing the pre-catalysts to the active species, the energy gaps epsilon(1) decrease dramatically from about 60 kcal mol(-1) to about 0 kcal mol(-1) for each complex, indicating the important activating role played by the co-catalyst. Finally, it is found that the energy difference values between different spin states relates to catalytic activities for both pre-catalyst and active species as well.

Interplay of anisotropy in shape and interactions in charged platelet suspensions.

Motivated by the intriguing phase behavior of charged colloidal platelets, we investigate the structure and dynamics of charged repulsive disks by means of Monte Carlo simulations. The electrostatic interactions are taken into account through an effective two-body potential, obtained within the nonlinear Poisson-Boltzmann formalism, which has the form of anisotropic screened Coulomb potential. Recently, we showed that the original intrinsic anisotropy of the electrostatic potential in competition with excluded volume effects leads to a rich phase behavior that not only includes various liquid-crystalline phases but also predicts the existence of novel structures composed of alternating nematic-antinematic sheets. Here, we examine the structural and dynamical signatures of each of the observed structures for both translational and rotational degrees of freedom. Finally, we discuss the influence of effective charge value and our results in relation to experimental findings on charged platelet suspensions.

Generalized polymer effective charge measurement by capillary isotachophoresis

In this work, we have generalized the use of capillary isotachophoresis as a universal method for determination of effective charge of anionic and cationic (co)polymers on ordinary capillary electrophoresis instruments. This method is applicable to a broad range of strong or weak polyelectrolytes with good repeatability. Experimental parameters (components and concentrations of leading and terminating electrolytes, capillary diameters, constant electric current intensity) were optimized for implementation in 100μm i.d. capillaries for both polyanions and polycations. Determined values of polymer effective charge were in a very good agreement with those obtained by capillary electrophoresis with indirect UV detection. Uncertainty of the effective charge measurement using isotachophoresis was addressed and estimated to be ∼5–10% for solutes with mobilities in the 20–50×10−9m2V−1s−1 range.

Correlating net charges and the activity of bis(imino)pyridylcobalt complexes in ethylene polymerization

A series of unsymmetrical bis(imino)pyridylcobalt complexes was investigated by DFT–QEq method to correlate the net charges of cobalt center and their catalytic activities. The effective net charge values on cobalt atom, calculated by QEq method at doublet spin state, reflected the influences of substituents within their ligands. The catalytic activities of these cobalt complexes in ethylene polymerization continuously increase along with higher values of the effective net charges on cobalt atom. The energy differences at doublet and quartet states kept the constant tendency for the cobalt complexes without the steric influences of substituents within ligands.

Application of variational principle to scattering problems

The validity of the variational principle for scattering problems is examined in the case of ionization of atomic hydrogen by electron impact. The effective charge seen by the scattered electron is determined mathematically in a rigorous way excluding any empirical assumptions. It is shown that the elaborated approach gives effective charge values that are reasonable and have clear physical meaning.