Negative Electric Field Research Articles

Theoretical study on fused 1,2,3,4-tetrazine-1,3-dinitroxide derivatives under external electric field.

Considering the excellent properties of 1,2,3,4-tetrazine-1,3-dinitroxides, several types of energetic derivatives have been synthesized from them. Among them, [1,2,5] oxadiazolo [3,4-e] [1,2,3,4]-tetrazine-4,6-Di-N-dioxide (FTDO), 5,7-dinitrobenzo-1,2,3,4-tetrazine-1,3-nitrogen dioxide (DTND), and [1,2,3,4] tetrazino [5,6-e] [1,2,3,4] tetrazine-1,3,8-tetraoxide (TTTO) are considered excellent energetic materials. However, there is limited research on their behavior under electric fields. The effect of electric fields was studied using density functional theory to calculate trigger bond changes, strain energy, chemical reactivity, and surface electrostatic potential. The results indicate that the planar structure of FTDO is more unique than that of DTND and TTTO, and its trigger bond is located at special position. Increased electric field strength can lengthen the trigger bond, increase sensitivity, and reduce strain energy of FTDO. Under a positive electric field, DTND and TTTO have longer trigger bond lengths, increased sensitivity, and increased strain energy, while exhibiting the opposite behavior under a negative electric field. Electric fields can affect the chemical reactivity of the all three derivatives. FTDO is less active under positive electric fields, DTND is more active under both electric fields, and TTTO becomes more active under negative electric fields. Finally, the electric field can expand their absorption spectrum range, affecting electron transfer between fragments. All calculations in this article were completed on Gaussian 16 software. The calculation levels are B3LYP/6-311G**, B3LYP/Def2-TZVPP, and PBE1PBE/6-311G**. Multiwfn and VMD were used for wave function analysis. Electric fields have a strength range of - 0.02 to 0.02 a.u., with a growth gradient of 0.01 a.u.

The tunable electronic band structure of a AlP3/Cs3Bi2I6Cl3 van der Waals heterostructure induced by an electric field: a first-principles study.

Constructing van der Waals heterostructures (vdWHs) has emerged as an attractive strategy to combine and enhance the optoelectronic properties of stacked materials. Herein, by means of first-principles calculations, we investigate the geometric and electronic structures of the AlP3/Cs3Bi2I6Cl3 vdWH as well as its tunable band structure via an external electric field. The AlP3/Cs3Bi2I6Cl3 vdWH is structurally and thermodynamically stable due to the low binding energy and the small energy fluctuation at room temperature. Our band structure calculations demonstrate that the AlP3/Cs3Bi2I6Cl3 vdWH possesses an indirect bandgap and a type-I band alignment with the band edges both dominated by an AlP3 layer. Notably, the band alignment of heterostructures can be flexibly tuned between type-I and type-II by employing an external electric field. Besides, an indirect-to-direct bandgap transition can be observed by increasing the intensity of negative electric field. These results reveal the potential of the AlP3/Cs3Bi2I6Cl3 vdWH as a novel candidate material for the experimental designs of multi-functional devices.

Effect of radial electric field on energy deposition for exploding 40- μ m diameter aluminum wire in vacuum with different conical–planar electrodes

Two series of conical wire holders were designed that can generate different values of positive (with outward direction) and negative (with inward direction) radial electric fields on wire surfaces in negative polarity wire electrical explosion (WEE) in vacuum. The influences of positive and negative radial electric fields on the evolution and axial inhomogeneity of the WEE were studied with the conical–planar electrodes. The results suggest that the radial electric field does have significant influence on the axial inhomogeneity in WEE. The positive radial electric field can increase the energy deposition, while the negative radial electric field can decrease the energy deposition, which then leads to different energy deposition structures. This study provides some help for better understanding of the axial inhomogeneity in the process of WEE; another potential use of the observed effect is to cause different sections of wire to explode at different times, which may introduce a possible approach for adjusting axial inhomogeneity of WEE through electric field regulation.

Theoretical analysis and performance optimization of Cs<sub>2</sub>AgBiI<sub>6</sub> solar cells with dual hole transport layers

Double perovskite materials have received significant attention in the photovoltaic field due to their low cost, environmental friendliness, and lead-free composition, which make them ideal candidates for next-generation solar cell applications. In this work, the photovoltaic performance of solar cells using Cs<sub>2</sub>AgBiI<sub>6</sub> as the light-absorbing layer is systematically investigated through simulations using Silvaco ATLAS software. Based on the previously reported single hole transport layer device architecture, namely ITO/ZnO/Cs<sub>2</sub>AgBiI<sub>6</sub>/HTL/Au, a new dual hole transport layer structure ITO/ZnO/Cs<sub>2</sub>AgBiI<sub>6</sub>/HTL1/HTL2/Au is proposed. Different dual hole transport layer combinations are explored, and their influence on the internal physical mechanism and the device performance are analyzed and optimized in detail. The simulation results show that the devices using Cu<sub>2</sub>O/NiO and NiO/Si respectively as dual hole transport layer significantly improve charge extraction and generate a negative electric field at the interface, thereby reducing recombination losse and accelerating the transport of hole carriers. These two configurations exhibit substantially higher efficiencies than those configurations with a single hole transport layer, confirming the advantages of the dual hole transport layer structure. Additionally, devices using Cu<sub>2</sub>O/CZTS and MoO<sub>3</sub>/CZTS as dual hole transport layer show better performance than the reference structure using Spiro-OMeTAD/CZTS, indicating the potential for further improvement by optimizing material selection and layer properties. Of the various dual hole transport layer combinations tested, the structure utilizing Cu<sub>2</sub>O/CZTS achieves the highest simulated power conversion efficiency (PCE) of 22.85%. By optimizing the thickness of each functional layer, the efficiency can be further increased to 25.62%, and the optimal layer thickness is determined to be 40 nm for ZnO, 850 nm for Cs<sub>2</sub>AgBiI<sub>6</sub>, 140 nm for Cu<sub>2</sub>O, and 150 nm for CZTS. Furthermore, the effects of environmental and material parameters, such as temperature and hole transport layer doping concentration, on device performance are investigated. This study lays a theoretical foundation for the design and enhancement of double perovskite solar cells. By demonstrating the potential that the dual hole transport layer structures can significantly improve device efficiency, their value in advancing environmentally friendly and lead-free photovoltaic technologies becomes very prominent. The insights gained from this research pave the way for developing high-performance double perovskite solar cells with optimized architectures and material properties.

First-principles study of nonlinear magnetoelectric effects in improper LuFeO3 multiferroics

Hexagonal LuFeO3 is known as an improper multiferroic material because of its ferroelectric structural distortion, measured by the Γ2− polar mode, and is driven by a trimerization structural distortion represented by the K3 non-polar mode [Fennie and Rabe, Phys. Rev. B 72, 100103(R) (2005)]. The K3 mode is also the primary structural origin of net weak ferromagnetism, associated with the ferromagnetic coupling between the in-plane geometrically frustrated spins. Here, we study the magnetoelectric coupling in LuFeO3 using first-principles calculations and applied external electric fields. We find that the weak ferromagnetism responds to the electric field polarization through the K3–Γ2− coupling, which is an intrinsic characteristic of improper multiferroics. Interestingly, the magnetoelectric coupling exhibits strong asymmetry under positive and negative electric fields. This nonlinearity is due to the competition between the K3 and the Γ2− modes according to Landau's theory and is related to asymmetrical interatomic interactions at the atomic level.

Observational Evidence of Negative Leader Reactivation Processes Following a Negative Return Stroke in Lightning Discharges

AbstractHigh‐time‐resolved mapping results of two rare reactivation processes following a negative return stroke are discovered and analyzed. At first, the discharges prior to the reactivation process were dominated by positive discharges lasting for tens of milliseconds in a limited space in the vicinity of a decayed negative leader channel. The positive discharges produced no detectable electric field change. Then, negative discharges started and propagated along the decayed downward negative leader channels at a speed exceeding 106 m/s for a few microseconds and produced negative electric field changes. The analysis reveals that the processes are physically distinct from recoil leaders and side discharges in terms of propagation behaviors, electromagnetic characteristics, and time scale. The possible mechanisms of the processes are discussed. The observation suggests that the reactivation processes of the negative leaders may lead to subsequent return strokes.

Multistage Linkage Internal Exclusion External Electrolyte Tactic Unlocks Extreme Fast Charge Lithium Metal Batteries.

Lithium metal batteries are booming because of their inherent preponderance, but a negative electric field from concentration dipolarization and slow solid-phase transfer at the electrode interface become blocking modules for extreme fast charging. Achieving an anion-rich solvation shell with a high dielectric constant (ε) is a feasible strategy to bootstrap an interface microenvironment for mass-transport reaction, but it is still an uncultivated field. Herein, the superposition, including the donor number values, the high ε, and the spatial potential resistance, are complementarily considered; we propose a low-cost electrolyte with an internal excluding external tactic to answer the above issue. Explanatorily, an optimized solvation shell follows the cascading exclusion relationship of nitrate ion (NO3-) → tetraglyme → ethylene carbonate → dimethyl carbonate. And the culminated bilayer structure establishes ideal conditions for Li+ transfer-reaction kinetics, of which an anion-rich internal shell facilitates solid-phase transport and a high-ε external shell slashes the negative electric field.

Combinatory electric-field-guided deposition for spatial microparticles patterning

Spatial deposition and patterning of microparticles are crucial in chemistry, medicine, and biology. Existing technologies like electric force manipulation, despite precise trajectory control, struggle with complex and personalized patterns. Key challenges include adjusting the quantity of particles deposited in different areas and accurately depositing particles in non-continuous patterns. Here, we present a rational process termed combinatory electric-field-guided deposition (CED) for achieving spatially regulated microparticle deposition on insulative substrates. This process involves coating the substrates with insulating materials like PVP and positioning it on a relief-patterned negative electrode. The negative electric field generated by the electrode attracts microparticles, while the positive surface charges on the substrates repel microparticles, resulting in the formation of a potential well over the electrode area. Consequently, this configuration enables precise control over microparticle deposition without the need for direct contact with the substrate's surface, simplifying the process of switching masks to meet varying microparticle deposition requirements. Furthermore, we demonstrate the customization of patterned microparticles on superhydrophobic coatings to regulate cell distribution, as well as the successful loading of drug-laden microparticles onto antibacterial bandages to match the areas of skin lesions. These applications underscore the versatility of CED across chemical, medical, and bioengineering domains.

Investigation on Enhancement of AP/HTPB/Al Composite Solid Propellant Combustion Characteristics via DC Electric Field

ABSTRACT To investigate the influence mechanisms of DC electric fields on the combustion of solid propellants, a numerical model for the combustion characteristics of AP/HTPB/Al composite solid propellant under the DC electric field is established. Effects of the applied electric field on combustion flame structure, combustion surface temperature distribution, and mixing fraction distribution are analyzed. The results indicate that the applied electric field enhances the mixing effect of the propellant gas phase decomposition products, thereby altering the flame structure and bringing it closer to the combustion surface. The application of the electric field leads to an increase in the combustion surface temperature by 20–70 K. The effect of the negative electric field on the combustion surface temperature and burning rate is more significant compared to that of the positive electric field. The results provide valuable theoretical guidance in the field of solid engine combustion control.

Superelastic electromechanical behaviors in ferroelectric PbTiO[formula omitted] ceramics under coupled mechanical-electric fields: Higher-order piezoelectric constitutive equations from first-principles

With the recent discovery of superelastic behaviors of ferroelectric (piezoelectric) ceramics, understanding their non-linear mechanical and electromechanical responses under high stress and electric field conditions is crucial for engineering and designing advanced piezoelectric devices, such as ultrasmall actuator systems. In this study, we carry out first-principles finite electric field calculations to clarify the mechanical and electromechanical properties under the electric field for typical ferroelectric ceramics of PbTiO3. Superelastic-like non-linear deformation behavior is enhanced or suppressed depending on the electric field direction, suggesting the possible design of superelasticity. We clarified that positive and negative electric fields to spontaneous polarization promote and inhibit deformation due to strain loading, thereby providing tunable superelasticity. We also investigate the mechanical loading and electric field dependence of the piezoelectric coefficient of PbTiO3. The tunable piezoelectric response can be provided with a coupling of mechanical loading and electric field. Finally, we present higher-order piezoelectric constitutive equations applicable for superelastic-like non-linear deformations under an electric field. The present results will open promising paradigms for functional piezoelectric devices, and the proposed piezoelectric constitutive equations broaden the design scope through finite element method analysis.

Investigation of the erosion mechanism of fluorine-free mold flux on the submerged entry nozzle under the influence of negative electric field

Fluorine-free mold flux is receiving increasing attention due to the environmental and health problems associated with using fluorinated flux in casting. However, the erosion problem in the submerged entry nozzle is still exists and not solved. Therefore, in this study, the electric field is used to improve the erosion resistance capability of the nozzle. The results show that a thick protective adhesion layer is formed on the surface of the slag-line material under the action of a negative electric field due to an electrochemical reaction. This protective layer further reacts with the CaO/SiO2 content of the fluorine-free slag-line material to generate an interfacial reaction layer composed mainly of Ca2SiO4 and CaZrO3. Due to the presence of Ca2SiO4 in the interfacial reaction layer, a small amount of crystalline transformation occurs during the cooling process. Thus, under the protection of the double protective layer generated by the action of the negative electric field, the slag-line material is not subject to the erosion of the fluorine-free mold flux, and the erosion rate is only 0.37%.

Controllable electrical contact characteristics of graphene/Ga2X3 (X = S, Se) ferroelectric heterojunctions

Reducing the interface barrier between metals and semiconductors is crucial for designing high-performance optoelectronic devices based on van der Waals heterojunctions (HJs). This study proposes four models of HJs composed of graphene (GR) and Ga2X3 (X = S, Se) and systematically investigates their interface electronic properties, along with strain engineering and electric field effects. The results indicated that exploiting the interface dipole-induced potential step allows modulation of the Schottky barrier height (SBH) and contact type of the HJs by altering the contact interfaces. In the BGR/Ga2S3 HJs (BGR means GR positioned at the bottom of Ga2X3), only a small positive (negative) electric field is required to realize the transition from n-type Schottky to p-type Schottky (Ohmic) contacts. Also, strain engineering provides additional means for flexible and controllable contact types, facilitating the design of reversible logic circuits. It indicates the physical insights and strategic interventions of GR/Ga2X3 HJs tunable SBH and offers theoretical guidance for the design of two-dimensional ferroelectric nanodevices with high-quality electrical contact interfaces.

Effects of external static electrical field on thermal and electrical conductivity in the Al-Cu, Al-Ni, and Al-Si eutectic alloys

This study aims to investigate the effects of external positive and negative static electric fields (E+ and E- respectively) on thermal conductivity (K) and electrical conductivity (σ) in Al-33 wt. % Cu, Al-6.4 wt. % Ni and Al-12 wt. % Si eutectic alloys. For this purpose, the solidifications of Al-Cu, Al-Ni, and Al-Si eutectic alloys were directionally done under E+ and E-. The directions of E were chosen to be parallel (E+) and antiparallel (E-) to the solid-liquid (S-L) growth direction and the magnitudes of E were approximately (+10) and (−10) kV cm−1 and (+16) and (-16) kV cm−1 for the Al-Cu, Al-Ni, and Al-Si eutectic alloys, respectively. The effects of E+ and E− on the K and σ were determined by the longitudinal heat flow and the four-point probe methods, respectively. While the K and σ values decreased with increasing temperature, the K and σ were increased and decreased with E+ and E−, respectively.

Abundant electric-field tunable symmetry-broken states in twisted monolayer-bilayer graphene

Electron-electron correlations can lift the high degeneracies in strong correlated systems, resulting in various symmetry-broken states. Twisted monolayer-bilayer graphene (tMBG) is an especially rich system due to its low crystalline symmetry. Here, we report abundant electric-field tunable symmetry-broken states in tMBG. The ground state at half filling of the conduction flat band is spin- and valley-polarization dominated under positive and negative electric field, respectively, consistent with our theoretical calculations. In addition, we find a symmetry-broken Chern insulator emanating from 1.5 electrons per moiré unit with C = 3 emerges at high magnetic field in a negative electric field range. The C = 3 suggests that one and a half flavor-polarized Chern 2 bands within the same valley are filled, consistent with the valley-polarization-dominated half-filling state under negative electric field, while the fractional filling stems from a density-wave state held by enlarged unit cells containing two moiré units.

Adsorption behavior of heptafluorobutyronitrile decomposition components on the Cu(1 1 1) surface

The interaction mechanism of heptafluorobutyronitrile (C4F7N) decomposition components with Cu(1 1 1) surface under the external electric fields is investigated by DFT and MD. The results show that nitrile gases as well as COF2 molecules have smaller orbital energy gaps compared to perfluorinated gases, making it easy for the C4F7N decomposition component to lose electrons during the interaction with the Cu(1 1 1) surface. The interaction energy of CF3CN and C2F5CN in nitrile gas with Cu(1 1 1) surface is weakened under external electric fields, while the two CN groups of C2N2 make it almost unaffected compared to CF3CN and C2F5CN. The MD study shows that some gas molecules accumulate on the Cu(1 1 1) surface when negative electric field is applied, while no gas molecules are found to accumulate on the Cu(1 1 1) surface when positive electric field is applied. Furthermore, as the temperature increases, the accumulation of gas molecules occurs in both positive and negative electric fields, among which nitrile gas molecules are predominate, which is not conducive to the compatibility of the gas-solid interface. The conclusions can provide theoretical guidance for the operation and maintenance of insulation equipment.

Photoelectric charging and lofting of dust particles on a conducting surface with external electric fields

We present a laboratory study of photoelectric charging of dust particles and their lofting on a conducting surface in the presence of external electric fields. Insulating particles with diameter <45 μm are dispersed on a conducting surface exposed to ultraviolet (UV) light. In addition to the UV exposure, a positive or negative external electric field is applied. Independent of the orientation of the external electric field, the dust particles are found to be positively charged but with different mechanisms. It is shown that the orientation of the external electric field controls the dynamics of photoelectrons emitted from the dust particles and the conducting substrate surface. Distinctly different lofting results are shown between these two electric field cases. The results provide insight for understanding dust charging and release and helping develop mitigation solutions in particle accelerators, semiconductor manufacturing, fusion reactors, and space exploration to planetary bodies.

Dry Reforming of Methane on Ni/LaZrO2 Catalyst under External Electric Fields: A Combined First-Principles and Microkinetic Modeling Study.

Dry reforming of methane (DRM) reaction has great potential in reducing the greenhouse effect and solving energy problems. Herein, the DRM reaction mechanism and activity on Ni16/LaZrO2 catalyst under electric fields were comprehensively investigated by combining density functional theory calculations with microkinetic modeling. The results showed that La doping increases the interaction between Ni and ZrO2 by Ni cluster transfer of more electrons. The adsorption strength of species followed the order Ni16/ZrO2 > Ni16/LaZrO2, which is consistent with the results for the d-band center but opposite to the metal-support interaction. The best DRM reaction path on Ni16/LaZrO2 was the CH2-O pathway, which is different from the CH-O pathway on Ni(111) and Ni16/ZrO2. Both positive and negative electric fields of strong and weak metal-support interactions reduced the energy barrier of DRM reaction. Importantly, our results showed that the more dispersed and smaller Ni12/LaZrO2 model by considering the dispersing effect induced by La doping, which displayed very different results from that of Ni16/LaZrO2: reduced the energy barrier for methane decomposition, thereby promoting DRM reaction activity. Microkinetic results showed that the carbon deposition behavior of DRM becomes weaker on Ni16/LaZrO2 due to the suppression of methane decomposition in the presence of La doping compared to Ni16/ZrO2, but the opposite result is obtained on Ni12/LaZrO2. The order of DRM reactivity was Ni16/LaZrO2 < Ni16/ZrO2 < Ni12/LaZrO2, which is consistent with the experiment observations. The conversion of methane and CO2 was higher in positive electric fields than in negative electric fields at low temperatures, but the results were opposite at high temperature. Negative electric fields can improve the carbon deposition resistance of Ni-based catalysts compared to positive electric fields. The degree of rate control analysis showed that CHx* oxidation also plays an important role in the DRM reaction. We envision that this study could provide a deeper understanding for guiding the widespread application of electric field catalysis.

Improving Aqueous Zinc Ion Batteries with Alkali Metal Ions.

Aqueous zinc (Zn) ion batteries have received broad attention recently. However, their practical application is limited by severe Zn dendrite growth and the hydrogen evolution reaction. In this study, three alkali metal ions (Li+, Na+, and K+) are added in ZnSO4 electrolytes, which are subjected to electrochemical measurements and molecular dynamics simulations. The studies show that since K+ has the highest mobility and self-diffusion coefficient among the four ions (Li+, Na+, K+, and Zn2+), it enables K+ to preferentially approach a zinc dendrite at an earlier time, driven by a negative electric field during a cathodic process. The electric double layer, with K+ around the negatively charged Zn dendrite, inhibits dendrite growth and mitigates the hydrogen evolution reaction on the Zn anode. Under this kinetic effect, the Zn-Zn symmetric cell with K+ exhibits a long cycling stability of 1000 h at 1 mA·cm-2 of 1 mAh·cm-2 and 190 h at 30 mA·cm-2 of 2 mAh·cm-2. Such a kinetic effect is also observed with additives Na+ and Li+, though less profound than that of K+.

Disparate External Electric Field Effect on the Adsorption and Shear Behavior of Monovalent and Trivalent Ions in Electrolyte Solution.

Reducing friction is of great interest, and an external potential applied to the friction pair can regulate lubricity. Electrochemical atomic force microscopy (EC-AFM) is used to study the tribological and adsorption behavior of monovalent and trivalent ionic solutions between charged surfaces. An opposite trend of coefficient of friction (COF) and normal force that varies with the applied electric potential is witnessed. Direct force measurements and theoretical models have disclosed that, for the NaCl solution, the negative electric field reduces the COF by increasing cation adsorption. As for LaCl3 solution, the positive electric field promotes the primary adsorption of anions on HOPG, resulting in the disappearance of the attractive ion-ion correlation between the trivalent ions, thereby reducing the COF. The shear behavior of adsorbed ions in electrolyte solution is sensitive to their valence, because of their different surface force contribution. The study further provides a framework to optimize the design of hydration lubrication.

A 3D Numerical Model to Estimate Lightning Types for PyroCb Thundercloud

Pyrocumulonimbus (pyroCb) thunderclouds, produced from extreme bushfires, can initiate frequent cloud-to-ground (CG) lightning strikes containing extended continuing currents. This, in turn, can ignite new spot fires and inflict massive harm on the environment and infrastructures. This study presents a 3D numerical thundercloud model for estimating the lightning of different types and its striking zone for the conceptual tripole thundercloud structure which is theorized to produce the lightning phenomenon in pyroCb storms. More emphasis is given to the lower positive charge layer, and the impacts of strong wind shear are also explored to thoroughly examine various electrical parameters including the longitudinal electric field, electric potential, and surface charge density. The simulation outcomes on pyroCb thunderclouds with a tripole structure confirm the presence of negative longitudinal electric field initiation at the cloud’s lower region. This initiation is accompanied by enhancing the lower positive charge region, resulting in an overall positive electric potential increase. Consequently, negative surface charge density appears underneath the pyroCb thundercloud which has the potential to induce positive (+CG) lightning flashes. With wind shear extension of upper charge layers in pyroCb, the lightning initiation potential becomes negative to reduce the absolute field value and would generate negative (−CG) lightning flashes. A subsequent parametric study is carried out considering a positive correlation between aerosol concentration and charge density to investigate the sensitivity of pyroCb electrification under the influence of high aerosol conditions. The suggested model would establish the basis for identifying the potential area impacted by lightning and could also be expanded to analyze the dangerous conditions that may arise in wind energy farms or power substations in times of severe pyroCb events.