External Electrostatic Field Research Articles

A scattering matrix approach to the effective mass dependence of tunneling current through heterojunctions

A scattering matrix technique is used to calculate the longitudinal and transverse energy dependence of the transmission probability through various heterostructures using both the BenDaniel–Duke (BD) and the lesser known Zhu–Kroemer (ZK) boundary conditions to take into account the spatial dependence of the effective mass. We first illustrate the large difference in the transmission probabilities calculated using both boundary conditions for the simple problems of tunneling through a potential step, a single rectangular barrier, and a resonant tunneling device. Then, we present numerical calculations of the external electric field dependence of the field emission (FE) current from a n-doped GaAs semiconductor/vacuum interface using both boundary conditions, showing that the BD boundary conditions underestimate the FE current for large values of the applied external electrostatic field. A comparison of calculated FE characteristics with FE data may be a way to determine the appropriate boundary conditions to solve tunneling problems through heterostructures with spatially varying effective mass.

Exploring α-synuclein stability under the external electrostatic field: Effect of repeat unit

Parkinson’s disease (PD) is a category of neurodegenerative disorders (ND) that currently lack comprehensive and definitive treatment strategies. The etiology of PD can be attributed to the presence and aggregation of a protein known as α-synuclein. Researchers have observed that the application of an external electrostatic field holds the potential to induce the separation of the fibrous structures into peptides. To comprehend this phenomenon, our investigation involved simulations conducted on the α-synuclein peptides through the application of Molecular Dynamics (MD) simulation techniques under the influence of a 0.1 V/nm electric field. The results obtained from the MD simulations revealed that in the presence of external electric field, the monomer and oligomeric forms of α-synuclein are experienced significant conformational changes which could prevent them from further aggregation. However, as the number of peptide units in the model system increases, forming trimers and tetramers, the stability against the electric field also increases. This enhanced stability in larger aggregates indicates a critical threshold in α-synuclein assembly where the electric field’s effectiveness in disrupting the aggregation diminishes. Therefore, our findings suggest that early diagnosis and intervention could be crucial in preventing PD progression. When α-synuclein predominantly exists in its monomeric or dimeric form, applying even a lower electric field could effectively disrupt the initial aggregation process. Inhibition of α-synuclein fibril formation at early stages might serve as a viable solution to combat PD by halting the formation of more stable and pathogenic α-synuclein fibrils.

Fuel effects on the electrostatic control of charged droplet trajectories

The use of electrostatic fields to control the trajectory of charged droplets is investigated as a new technology to enhance mixing in liquid-fuelled combustors. The canonical configuration of a spray in crossflow is numerically studied with a focus on the effects of the fuel type on the onset of charge-induced breakup and droplet trajectories for a range of bulk flow velocities and electrostatic field strengths at conditions relevant to gas turbine applications. The investigated fuels are ethanol, n-heptane, and n-decane. Operational maps for each fuel are provided to assist the selection of the external electrostatic field required to achieve a balance between the drag and electrostatic forces, and enable a system design that considers fuel flexibility. The results demonstrate that the fuel type has an important impact on the diameter at which the charge-induced breakup is achieved, which mainly depends on the droplet equilibrium temperature. It is also shown that, for cases where the droplet net charge is fixed to a given fraction of the maximum possible charge (based on the Rayleigh limit), the temperature of the droplet at injection could be used as a parameter to control the onset of secondary breakup. Analysis of the strength of the electrostatic field necessary to achieve droplet stabilisation in a bulk flow shows that a balance between the electrostatic and drag forces can only be achieved for relatively low values of the bulk flow velocity, if the strength of the electrostatic field is kept below the breakdown limit of the carrier phase. This balance mainly depends on the droplet net charge and flow conditions, whereas the effect of the type of fuel on the drag force is less important. When the charge is imposed as a fraction of the maximum possible value at injection, for low values of the bulk flow velocity, the strength of the electrostatic field that balances the drag tends to become independent of the droplet diameter for a wide range of droplet sizes. Further investigation of the trajectories of evaporating droplets demonstrates that, although affected by the type of fuel through the evaporation rate, with the same settings of the electrostatic field, it is possible to achieve evaporation in a confined region for all the fuels and ambient conditions studied in this work once the initial droplet charge and initial droplet diameter are fixed. The present findings offer new insights for the development of future technologies for fuel preparation with enhanced mixing and fuel flexibility.

Exploring the connection between non‐uniform electrostatic fields generated by opposite polarity voltages and the behavior of atmospheric pressure plasma jet

AbstractThis study investigates the counterintuitive behaviors of a microwave‐induced atmospheric pressure plasma jet (APPJ) under the influence of an external electrostatic field applied by one or a pair of parallel electrode plates subjected to DC voltages. The findings demonstrate that the plasma jet consistently deflects toward the electrode plate with an electrostatic potential, irrespective of the direction of the applied field. The deflection becomes more pronounced with increasing voltage on the electrode plate until the ionic wind generated by the high voltage significantly affects the jet's behavior. Remarkably, a negative voltage induces a greater deflection compared to a positive voltage. To further investigate this discovery, the dielectric properties and the non‐neutral characteristics of the APPJ are analyzed, and the simulations of the electric field distribution reveal a non‐uniform distribution, which plays a crucial role in understanding the mechanism behind the observed behaviors of the plasma jet. This study provides a comprehensive understanding of the underlying mechanism driving the observed phenomena and sheds light on the collective behavior of plasma jets under non‐uniform electric fields. The findings of this study offer valuable guidelines for investigating and controlling the behavior of APPJs.

On the Issue of Calculating the Magnitude of Induced Charges and the Electrostatic Dipole of an Oblate Spheroid with an Axis of Symmetry Collinear to the External Homogeneous Electrostatic Field

On the Issue of Calculating the Magnitude of Induced Charges and the Electrostatic Dipole of an Oblate Spheroid with an Axis of Symmetry Collinear to the External Homogeneous Electrostatic Field

An algorithm to find the optimal oriented external electrostatic field for annihilating a reaction barrier in a polarizable molecular system.

The use of oriented external electric fields (OEEFs) to promote and control chemical reactivity has motivated many theoretical and computational studies in the last decade to model the action of OEEFs on a molecular system and its effects on chemical processes. Given a reaction, a central goal in this research area is to predict the optimal OEEF (oOEEF) required to annihilate the reaction energy barrier with the smallest possible field strength. Here, we present a model rooted in catastrophe and optimum control theories that allows us to find the oOEEF for a given reaction valley in the potential energy surface (PES). In this model, the effective (or perturbed) PES of a polarizable molecular system is constructed by adding to the original, non-perturbed, PES a term accounting for the interaction of the OEEF with the intrinsic electric dipole and polarizability of the molecular system, so called the polarizable molecular electric dipole (PMED) model. We demonstrate that the oOEEF can be established by locating a point in the original PES with unique topological properties: the optimal barrier breakdown or bond-breaking point (oBBP). The essential feature of the oBBP structure is the fact that this point maintains its topological properties for all the applied OEEFs, also for the unperturbed PES, thus becoming much more relevant than the commonly used minima and transition state structures. The PMED model proposed here has been implemented in an open access package and is shown to successfully predict the oOEEF for two processes: an isomerization reaction of a cumulene derivative and the Huisgen cycloaddition reaction.

On modal decomposition as surrogate for charge-conservative EHD modelling of Taylor Cone jets

The dynamics of the interface of a fluid jet subjected to an external electrostatic field forming a Taylor cone jet is investigated using a numerical approach. A charge-conservative electrohydrodynamic model is used. In this model, the reduced form of Maxwell’s equations for an electrostatic field, a transport equation for electric charges and the Navier–Stokes equations for a laminar flow are solved. The connection between the electric field and the hydrodynamic flow is established by the Maxwell stress tensor, which ensures the description of the electric surface forces. A fluid volume model based on surface compression provides an efficient and robust modulation of the overall behaviour of the electric drive of immiscible flows. Test cases from the literature López-Herrera et al. (2011); Roghair et al. (2015) help us to validate the numerical model. The order of accuracy of the spatial and temporal discretization of the electric field equations is computed through a quasi one-dimensional test case. The primary decay of a Taylor cone beam is then simulated with uniform droplet emission. This simulation is validated with experimental results from the literature Taylor (1969). To analyse the dynamics of the flow, it is proposed to use decomposition methods such as Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) using snapshots of the flow field. The dynamic structures formed by the velocity field and the dynamics of the electric charge determine the fundamental dynamics of the droplet emission. An analysis of the sensitivity of the modes to the sampling frequency is performed. The influence of different inlet velocities on the decomposition is analysed in the spatial and frequency domain. A reduced-order model (ROM) is interpolated from the base POD, and we demonstrate that it can be used to successfully construct the velocity and electric charge along the field. We anticipate numerous applications of this new type of ROM, such as for accelerating electrohydrodynamic calculations as surrogate models in digital twins.

Tunable optical differential operation based on graphene at a telecommunication wavelength.

Optical differential operation based on the photonic spin Hall effect(SHE) has attracted extensive attention in image processing of edge detection, which has advantages of high speed, parallelism, and low power consumption. Here, we theoretically demonstrate tunable optical differential operation in a four-layered nanostructure of prism-graphene-air gap-substrate. It is shown that the spatial differentiation arises inherently from the photonic SHE. Furthermore, we find that the transverse spin-Hall shift induced by the photonic SHE changes dramatically near the Brewster angle with the incident angle increases at a telecommunication wavelength. Meanwhile, the Fermi energy of graphene and the thickness of the air gap can affect the transverse spin shift. Interestingly, we can easily adjust the Fermi energy of graphene in real time through external electrostatic field biasing, enabling fast edge imaging switching at a telecommunication wavelength. This may provide a potential way for future tunable spin-photonic devices, and open up more possible applications for artificial intelligence, such as target recognition, biomedical imaging, and edge detection.

On the Calculation of the Magnitude of Induced Charges and the Electrostatic Dipole of an Oblate Spheroid with an Axis of Symmetry Collinear to an External Homogeneous Electrostatic Field

The values of the surface induced charges, the positions of their centers and the value of the equivalent dipole of an oblate conducting spheroid are determined by transition from spheroidal coordinates to a spherical system of coordinates in the analytical asymptotic calculations of the first order of smallness with respect to the squared eccentricity. The characteristics of the equivalent dipole are obtained depending on the value of the electrostatic field strength, squared eccentricity, and the radius of an equal sphere.

On Electromagnetic Radiation Associated with the Zero and First Modes of a Droplet Oscillating in an External Electrostatic Field

On Electromagnetic Radiation Associated with the Zero and First Modes of a Droplet Oscillating in an External Electrostatic Field

Effects of external magnetic and electric field on multipactor and plasma breakdown of high-power microwave window

In this work, we investigated the effects of an external magnetic field, a DC electrostatic field, and a normal rf electric field on the multipactor and plasma ionization breakdown process near a microwave window by performing kinetic particle-in-cell/Monte Carlo collision simulations, and the underlying mechanism is also given. The magnetic field, parallel to the surface and perpendicular to the tangential rf field, can effectively suppress the electron multipactor process by delaying the electron incidence on the dielectric window and push the plasma breakdown bulk away from the dielectric window. However, when the magnetic field is too strong, the mitigation effect is not significant, and may even enhance the multipactor process at the beginning of the plasma breakdown. The external DC electrostatic field, perpendicular to the surface, can inhibit electron multipactor when it points toward the surface. On the other hand, when the DC electric field direction is reversed, then the electron multipactor process is found to be promoted, and the gas ionization bulk is closer to the dielectric window. The external normal rf electric fields perpendicular to the surface with small amplitudes are found to be capable of promoting the multipactor process. With increasing the amplitude of normal rf electric field, the multipactor process can be suppressed to some degree at the initial stage of the plasma breakdown and the gas ionization bulk region is kept away from the dielectric window surface.

Experimental study of CO2 hydrate formation under an electrostatic field

The hydrate-based CO2 capture and storage technique is cutting-edge and promising, but it exhibits slow formation rates and insufficient gas storage capacity, making commercialization challenging. In this work, the CO2 hydrate formation process in fresh water, memory water, and saltwater systems under the electrostatic field was studied, and the influence mechanism of the electrostatic field on the CO2 hydrate formation was discussed. Experimental results showed that the nucleation and growth of CO2 hydrate could be affected by the electrostatic field. The nucleation of CO2 hydrate could be promoted in the presence of an electrostatic field. In the fresh water system, the completion of hydrate formation was 54.5% faster with the 150 V application compared to the one without the electrostatic field. The introduction of an external electrostatic field causes a further reduction in the system's free energy. In the memory water system, the residual hydrate cage fragments could promote the reformation process of hydrate. Nevertheless, the presence of the electrostatic field could weaken the memory effect. In the salt water system, the electrostatic field could promote hydrate formation after the stage of dissolution. Due to the collision of ions with hydrate nuclei, however, the completion time of hydrate formation was increased. This study is anticipated to provide novel insights into the promotion of hydrate formation through the implementation of an electrostatic field.

Single-atom catalysis for carbon dioxide dissociation using greigite-supported M1/Fe3S4(111) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) under electrostatic fields

Single transition metal adatoms (M) supported on a solid surface – here the reactive greigite Fe3S4(111) surface – combine the best properties of homogeneous and heterogeneous catalytic systems and are highly selective materials capable of altering the pathway of difficult reactions. We have employed state-of-the-art first-principles simulations to investigate the process of carbon dioxide (CO2) dissociation on the single-atom catalyst (SAC) M1/Fe3S4(111). We discuss how reconstructions of the symmetrical stacking sequence of charged atomic planes determines the possible stable non-polar terminations of the Fe3S4(111) surface. The thermodynamic stability and the work function are the main descriptors that are affected by external electrostatic fields, both for the most stable termination of the pristine Fe3S4(111) surface as well as the M1/Fe3S4(111) catalysts. We present the electron density plots for the M1/Fe3S4(111) surfaces, which show that the M adatom forms covalent metal-support interactions (CMSI). In general, positive external electrostatic fields enhance the adsorption properties of the M1/Fe3S4(111) catalysts towards the CO2 molecule, which activates chemically upon interaction. Our energy profiles for the dissociation of the CO2 molecule show that carefully selected transition metal adatoms, such as V, Cr and Co, and positive external electrostatic fields can be used to tune the catalytic properties of SACs.

Nonlinear spectral features of the relativistic interaction between electron and ultrashort laser pulse

Features of the radiation spectra are investigated with the quantum electrodynamic theory for the nonlinear scattering interaction between relativistic electron and few-cycle linearly polarized laser pulse. The angle between the moving direction of the electron and that of the laser pulse affects the scattered radiation characteristics. When the electron has a head-on collision with the laser pulse having a carrier envelope phase as zero, the angular distribution of the scattered radiation spectrum is symmetrical with respect to the laser pulse propagation direction. Such a symmetry disappears when the electron collides with the laser obliquely and the direction of most of the radiation energy shifts at an acute angle towards the electron direction. The CEP has significant effects on the spectral angular distribution. The CEP influence is determined by the exertion of the electromagnetic field on the motion of the electron, whose trajectory overlap in phase space leads to the interference between scattered radiation in different intervals of the interaction process. The supercontinuum radiation could be produced under certain CEPs. An external electrostatic field applied as the environment for the laser-electron interaction is another important factor affecting the scattered radiation features by modulating the harmonic components and their angular distribution. This study may help the analysis of the spectral data from relativistic laser-solid target experiments.

Atomistic insight into the effects of electrostatic fields on hydrocarbon reaction kinetics.

Reactive Molecular Dynamics (MD) and Density Functional Theory (DFT) computations are performed to provide insight into the effects of external electrostatic fields on hydrocarbon reaction kinetics. By comparing the results from MD and DFT, the suitability of the MD method in modeling electrodynamics is first assessed. Results show that the electric field-induced polarization predicted by the MD charge equilibration method is in good agreement with various DFT charge partitioning schemes. Then, the effects of oriented external electric fields on the transition pathways of non-redox reactions are investigated. Results on the minimum energy path suggest that electric fields can cause catalysis or inhibition of oxidation reactions, whereas pyrolysis reactions are not affected due to the weaker electronegativity of the hydrogen and carbon atoms. MD simulations of isolated reactions show that the reaction kinetics is also affected by applied external Lorentz forces and interatomic Coulomb forces since they can increase or decrease the energy of collision depending on the molecular conformation. In addition, electric fields can affect the kinetics of polar species and force them to align in the direction of field lines. These effects are attributed to energy transfer via intermolecular collisions and stabilization under the external Lorentz force. The kinetics of apolar species is not significantly affected mainly due to the weak induced dipole moment even under strong electric fields. The dynamics and reaction rates of species are studied by means of large-scale combustion simulations of n-dodecane and oxygen mixtures. Results show that under strong electric fields, the fuel, oxidizer, and most product molecules experience translational and rotational acceleration mainly due to close charge transfer along with a reduction in their vibrational energy due to stabilization. This study will serve as a basis to improve the current methods used in MD and to develop novel methodologies for the modeling of macroscale reacting flows under external electrostatic fields.

On the Electromagnetic Radiation Associated with Zero and First Modes of a Droplet Oscillating in an External Electrostatic Field

The paper deals with electromagnetic radiation generated by capillary oscillations of the zero and first modes of oscillations of a droplet in an external electrostatic field. It is assumed that the droplet of an ideal incompressible electrically conductive liquid has a zero total electric charge and that it is charged in an external uniform electrostatic field by induced charges of opposite signs. The radiation under discussion is detected via analytical asymptotic calculations of the second order infinitesimal by the dimensionless amplitude of the droplet oscillations in an external electrostatic field. An analytical expression was found for the intensity of the electromagnetic radiation associated with oscillations of the zero and first modes, and the dependence of the intensity of radiation on the value of the field strength, the droplet size, and the value of the surface tension coefficient.

High order harmonic spectra of CO under external electrostatic field

In this work, we use Lewenstein’s theory to calculate the high order harmonic spectra of CO molecule in a linearly polarized laser field combined with an external electrostatic field. The results show that the characteristics of the high order harmonic spectra of CO molecule depend strongly on the direction of the external static electric field relative to the orientation of CO. Especially, when the direction of the external static electric field points from O to C, the plateau of the harmonic spectrum becomes wider and the cutoff frequency reaches a larger value than the scenario without external static electric field. When the direction of the external static electric field points from C to O, the harmonic spectrum shows a double-plateau structure. Using Lewenstein theory, these phenomena can be understood from the viewpoint that the harmonic generation comes from a coherent superposition of the contributions of two kinds of channels characterized by C-end ionization and O-end ionization. The C(O)-end ionization channel means that the electron is ionized from C(O) end, then accelerated by the driving electric field, finally recombines with its parent molecular ion at either C or O end, emitting the harmonics. For the same harmonic order, the contribution of the C-end ionization channel is greater than that of the the O-end ionization channel. The two kinds of channels emit harmonics in adjacent half period of laser, where the external static electric field causes the cutoff frequency of the harmonic spectrum to increase and decrease in the adjacent half period of the laser field. Especially, when the direction of external static electric field is from the C to O, the cutoff frequency of the harmonic spectrum of the C-end ionization channel decreases, resulting in a higher first plateau in the spectrum. While, the increase of cut-off frequency of the O-end ionization channel will result in a lower second plateau. When the direction of external static electric field is reversed, the cutoff frequency of the harmonics of the C-end channel increases, leading the plateau of CO harmonic spectrum to become wider than that without the external static electric field. The cut-off frequency of the O-end ionization channel decreases. Because the contribution of the O-end ionization channel can be ignored compared with that of C-end ionization channel, the C-end channel dominates the contribution to harmonic generation and hence there is only one plateau in the harmonic spectrum. This work provides a clear physical picture for the formation of a double-plateau structure of CO harmonic spectra under the action of an external static electric field.

Transport properties of layered heterostructures based on conducting polymer

Polydiphenylenephthalide (PDP) belongs to the class of organic dielectrics, which exhibit electric conductive properties when an external electrostatic field and/or mechanical stress are applied. In this work, the transport properties of thin-film layered lead-PDP-lead structures were experimental-ly studied in a wide temperature range. At sufficiently high temperatures, the volt-ampere depend-ences are satisfactorily described in terms of the injection model of currents limited by the space charge. At temperatures below ~7.5 K, a number of samples exhibit features that can be explained by the effect of induced superconductivity in a thin film of a conducting polymer enclosed between two massive superconductors (lead). Keywords: thin films, conducting polymer, superconductivity.

Modeling and Simulation of PGGP Electrode Configuration for Ion-Extraction Process Using 2.5D-PIC Code

The ion extraction from laser-induced photoplasma in an electrostatic field is investigated by a 2.5-D-electrostatic particle-in-cell (PIC) code. The external electrostatic field is applied by a plate–grid–grid–plate (PGGP) electrode configuration. In this configuration, two additional grids are introduced in a parallel plate electrode configuration. Basically, these grids are kept at more negative potential than the cathode, and therefore, the grid extracts the ion, whereas plates collect the ions. Through such biasing, the sputtering of the already collected ions on the collecting plate can be avoided. The present investigation emphasizes on spatiotemporal evolution of photoplasma in the PGGP electrode configuration. Subsequently, investigate the performance of this electrode configuration with different biasing of electric potential. Finally, it compares the performance of PGGP with parallel plate and M-type electrode configurations. Based on this comparative analysis, an improved design of the PGGP electrode configuration is suggested. In addition, it also explains modeling aspects of different electrode geometries using 2.5-D-PIC, which includes the boundary conditions for Poisson’s equation, particle boundary conditions, and grid designing.

Транспортные свойства слоистых гетероструктур на базе проводящего полимера

Polydiphenylenephthalide (PDP) belongs to the class of organic dielectrics, which exhibit electric conductive properties when an external electrostatic field and/or mechanical stress are applied. In this work, the transport properties of thin-film layered lead–PDP–lead structures were experimental-ly studied in a wide temperature range. At sufficiently high temperatures, the volt–ampere depend-ences are satisfactorily described in terms of the injection model of currents limited by the space charge. At temperatures below ~7.5 K, a number of samples exhibit features that can be explained by the effect of induced superconductivity in a thin film of a conducting polymer enclosed between two massive superconductors (lead).