Effect Of External Electric Field Research Articles

First-principles study of the electronic and optical properties of two-dimensional PtS2/GaS van der Waals heterostructure

Heterostructures based on two-dimensional materials have received increasing attention due to their extraordinary properties and application potential. In this paper, the electronic and optical properties of the PtS2/GaS van der Waals (vdW) heterostructure as well as the effects of biaxial strain and external electric field are systematically investigated based on first-principles calculations. The PtS2/GaS vdW heterostructure has an interlayer distance of 3.01 Å and is a type-Ⅱ semiconductor of band gap 1.54 eV. Large optical absorption coefficients are observed in both the ultraviolet and the visible regions. Furthermore, its band structure can be effectively tuned by applying biaxial strain and external electric field. The transition between the type-Ⅱ and type-I band alignments can be realized. The absorption spectra and their peaks can be then manipulated effectively by applying biaxial strain with good stability under external electric field. The predicted tunable electronic properties and unique optical absorption properties suggests promising potential for the application of the PtS2/GaS vdW heterostructure in future optoelectronic nanodevices.

Exciton Delocalization and Polarizability in Perylenetetracarboxylic Diimide Probed Using Electroabsorption and Fluorescence Spectroscopies.

Perylenetetracarboxylic diimide (PTCDI) is an n-type organic semiconductor molecule that has been widely utilized in numerous applications such as photocatalysis and field-effect transistors. Polarizability and dipole moment, which are inherent properties of molecules, are important parameters that determine their responses to external electric and optical fields, physical properties, and reactivity. These parameters are fundamentally important for the design of innovative materials. In this study, the effects of external electric fields on absorption and fluorescence spectra were investigated to obtain the PTCDI parameters. The PTCDI substituted by an octyl group (N,N'-Dioctyl-3,4,9,10-perylenedicarboximide) dispersed in a polymethyl methacrylate (PMMA) matrix was studied in this work. The features of vibronic progression in the absorption spectrum were analogous to those observed in solution. The red shift of the absorption band caused by the Stark effect was mainly observed in the presence of an external electric field. Changes in parameters such as the dipole moment and polarizability between the ground and the Franck-Condon excited states of the PTCDI monomer were determined. The fluorescence spectrum shows a contribution from a broad fluorescence band at wavelengths longer than the monomer fluorescence band. This broad fluorescence is ascribed to the excimer-like fluorescence of PTCDI. The effects of the electric field on the fluorescence spectrum, known as the Stark fluorescence or electrofluorescence spectrum, were measured. Fluorescence quenching is observed in the presence of an external electric field. The change in the polarizability of the monomer fluorescence band is in good agreement with that of the electroabsorption spectrum. A larger change in the polarizability was observed for the excimer-like fluorescence band than that for the monomer band. This result is consistent with exciton delocalization between PTCDI molecules in the excimer-like state.

Investigation into the Heat Transfer Behavior of Electrostatic Atomization Minimum Quantity Lubrication (EMQL) during Grinding

Electrostatic atomization minimum quantity lubrication (EMQL) technology has been developed to address the need for environmentally friendly, efficient, and low-damage grinding of challenging titanium alloy materials. EMQL leverages multiple physical fields to achieve precise atomization of micro-lubricants, enabling effective lubrication in high temperature, high pressure, and high-speed grinding environments through the use of electric traction. Notably, the applied electric field not only enhances atomization and lubrication capabilities of micro-lubricants but also significantly impacts heat transfer within the grinding zone. In order to explore the influence mechanism of external electric field on spatial heat transfer, this paper first comparatively analyzes the grinding heat under dry grinding, MQL, and EMQL conditions and explores the intensity of the effect of external electric field on the heat transfer behavior in the grinding zone. Furthermore, the COMSOL numerical calculation platform was used to establish an electric field-enhanced (EHD) heat transfer model, clarifying charged particles’ migration rules between poles. By considering the electroviscous effect, the study reveals the evolution of heat transfer structures in the presence of an electric field and its impact on heat transfer mechanisms.

Theoretical predicted Janus SrAlGaTe4: effects of strain and electric field and its topological properties

The asymmetric Janus SrAlGaTe4, constructed from its parent SrGa2Te4 monolayer, was predicted theoretically by first principle calculations. Its stability was confirmed by phonon structure without imaginary frequency and ab initio molecular dynamics (AIMD) simulations. The Janus structure reduces the symmetry of SrGa2Te4 monolayer, which causes the absence of topological states in free-standing Janus SrAlGaTe4. To explore the possible electronic and topological properties, the effects of strain and external electric field, working as effective modulation methods for the electronic properties, were investigated. The SrAlGaTe4 monolayer undergoes a direct-to-indirect bandgap transition when the in-plane biaxial compressive strain is −8%. When the tensile strain is 9% or the electric field is 0.5 V Å−1, the Janus SrAlGaTe4 monolayer exhibits topological insulator (TI) characters, which was confirmed by the evolution of the Wannier charge centers (WCC). And the critical values for the topological transition are 2% for the biaxial tensile strain, and 0.2 V/Å for the applied electric field. The asymmetric Janus structure induces a Rashba spin splitting not only in the valence band but also in the conduction band near the Fermi level when the spin–orbit coupling (SOC) is present. Our findings offer theoretical insights into the exotic physical properties of SrAlGaTe4 and also provide guides to new spintronic device designs.

External electric field and UV-ozone treated Ti3C2T x -MXene nanosheets and their hole injection tailoring in UV organic light-emitting diodes

Solution-processed 2D nanosheets of Ti3C2T x -MXene have been facilely synthesized with ultrasonic-assisted liquid phase exfoliation. X-ray diffraction, scanning electron microscope, transmission electron microscope, atomic force microscopy and x-ray photoelectron spectroscopy measurements confirm that the Ti3C2T x -MXene nanosheets have been successfully synthesized, showing good film morphology and exceptional electronic properties. The comprehensive properties of Ti3C2T x -MXene nanosheets are systematically optimized by combination with appropriate sizes of Ti3C2T x -MXene nanosheets, external electric field and ultraviolet (UV)-ozone treatment. With Ti3C2T x -MXene nanosheets as hole injection layer and PBD as emissive molecule, UV organic light-emitting diodes (OLEDs) have been configurated and shown superior performance with maximum radiance of 1.47 mW cm−2, maximum external quantum efficiency of 1.084% and electroluminescent peak around 400 nm. The effects of external electric field and UV-ozone treatment on hole injection ability of Ti3C2T x -MXene nanosheets are investigated in details and further analyzed with impedance spectroscopy. Our experiments pave an alternative approach for advancing Ti3C2T x -MXene nanosheets and UV OLEDs.

Electric Field Controlled Anisotropic Rashba Splitting in Janus Chromium Dichalcogenide Monolayers : A Computational Study based on Density Functional Theory

In this study, we explore the electronic structure of Janus Chromium Dichalcogenide monolayers CrXY (X ≠ Y = S, Se, Te) in the first Brillouin zone using Density Functional Theory. Due to the mirror symmetry break and strong SOC in the crystal structure of Janus Chromium Dichalcogenide monolayer, we discovered Rashba splitting at Γ points in the first Brillouin zone. We analyze this anisotropy of Rashba splitting using k∙p perturbation theory and group symmetry analysis. By giving the effect of external electric field, we manipulate the characteristics of Rashba splitting on the Janus Chromium Dichalcogenide monolayer. The manipulation of Rashba splitting by applying external electric field, shows that the Janus Chromium Dichalcogenide monolayers has the potential for spintronic devices.

Effect of external electric fields on the ESDPT process and photophysical properties of 1,8-dihydroxy-2-naphthaldehyde.

In this work, by capitalizing on the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) methods, it has been systematically studied that the excited state double intramolecular proton transfer (ESDPT) process and the photophysical properties of 1,8-dihydroxy-2-naphthaldehyde (DHNA) are affected by the distinct external electric fields (EEFs). The obtained intramolecular hydrogen bond (IHB) parameters containing bond lengths and angles, as well as infrared (IR) vibrational spectra demonstrate that IHB strength changes in the distinct EEFs. Moreover, not only do the potential energy surfaces (PESs) indicate that the ESDPT process of DHNA is stepwise, but also increasing the positive EEF results in a decrease in the energy barrier accordingly, while vice versa. The absorption and fluorescence spectra also undergo a corresponding red or blue shift in the EEF; for instance, when the EEF changes from +10 × 10-4 a.u. to +20 × 10-4 a.u., the fluorescence peak undergoes a blue shift from 602 nm to 513 nm in the keto2 form. In a nutshell, the ESDPT process of DHNA can be influenced by the EEF, which will serve as a reference in regulating and controlling proton transfer that causes luminescence.

The Effect of External Electric Field on The Electrical and Magnetic Properties of NiCl2 Monolayer with Density Functional Theory

The study utilized density functional theory (DFT) to investigate the impact of spin-orbit interaction and external electric fields on the NiCl2 monolayer. The results demonstrated a reduction in the energy band gap and a transition from an indirect semiconductor to a metal when different electric fields were applied. Additionally, the combination of external electric fields and spin-orbit interactions altered the band structure of the NiCl2 monolayer, leading to a transition from a semiconducting state to a metallic state. These findings have significant implications for spintronic device design, as they suggest the potential for controlling the electrical and magnetic properties of the NiCl2 monolayer, making it suitable for use in alternative spintronic devices.

Regulation of photoinduced charge transfer in all-small-molecule organic solar cells through the synergistic effect of external electric field and solvent

The donor (BTR-Cl) and acceptor (BTP-FCl-FCl) have well-defined small molecule properties and excellent repeatability, and they can form charge transfer complexes with a wide spectral absorption range. Using density functional theory (DFT), we simulate the photoinduced charge transfer of bulk-heterojunction (BHJ) organic solar cell (OSC) materials modulated by the external electric field (Fext) at the microscopic level. The excited-state properties, reorganization energy (λ), Gibbs free energy (ΔG), electron coupling matrix elements (VDA) and intermolecular charge transfer (ICT) rate dependent on Fext are systematically analyzed. The results manifest that Fext has apparent positive regulation on the charge separation rate (KCS), and VDA is the main factor affecting KCS. The synergistic effect of solvent and Fext on charge transfer process is further investigated. It is found that the charge transfer rate in solvent is lower than that in solvent-free conditions, and the charge transfer rate in chlorobenzene (CB) solvent does not change significantly under the control of Fext. At the same time, Fext has a positive effect on the charge transfer rate in tetrahydrofuran (THF) solvent. Considering the charge transfer rate under different solvents and Fext intensities, it is found that the solvent and Fext play an essential role in determining the KCS and charge recombination rate (KCR).

Alteration in electroosmotic flow of couple stress fluids through membrane based microchannel

The fundamentals of electroosmosis are the most fascinating mechanism to induce flow of ionic solution under the effect of external electric field. The electroosmotic flow of the couple stress fluid in a microchannel with an active membrane pumping is analysed in the present model. The upper wall experiences membrane kinematics, generates the pressure to drive the fluid in the microchannel. Governing equations are formulated based on the mass and momentum conservation, and electric potential distribution of ions in diffuse layer. The suitable boundary conditions for the model have been considered. An analytical approach is employed to derive the solutions under the lubrication approximation, and the Debye–Hückel approximation. The effects of electric double layer thickness, couple stress parameter, and Helmholtz-Smoluchowski velocity on the velocity profile, pressure difference, net flow rate, induced streamline velocity, and local wall shear stress are computed for discussion of the physical significance of the model and its applications. Results reveal that electroosmosis mechanisms (axial electric field and electric double layer thickness) has remarkable role in modulating the fluids (Newtonian and non-Newtonian) flow driven by the rhythmic propulsion of membranes in microchannel. It is also worth mentioning that non-Newtonian fluids (couple stress fluids) need more external forces (electric force) to be pumped as compared to Newtonian fluids. Furthermore, it can be analysed that thinner electric double layers (EDLs) elevate wall shear stress, whereas stronger electric fields result in decreased wall shear stress. The results of the model help in designing smart membrane based electric pump for the use in various microscale transport phenomena of bio microfluidics systems.

Effect of temperature and external electric field on proton transport in ordered and amorphous proton exchange membranes: A molecular dynamics study

Proton exchange membrane (PEM) is a key component of proton exchange membrane fuel cell, and its proton conductivity directly affects the performance of fuel cell. Imparting order to Nafion molecules is one of potential effective approaches that can significantly improve the proton transport performance of PEM, but the underlying mechanism of this effect as well as the regulatory mechanism is unknown. In order to investigate the regulatory mechanism of temperature, electric field, and water content on the transport mechanism of the PEM and compare the transport properties between ordered and amorphous membranes, this study examined the proton migration rate of ordered and amorphous membranes under different electric field and water contents at 300 K and 350 K with molecular dynamics methods. The simulation results indicate that the ordered PEM exhibits better proton conductivity compared with the amorphous PEM due to its ordered structure with smoothly connected proton transport channels. The proton conductivity of the ordered PEM with a water content of 16 exhibits a remarkably high proton conductivity of 0.153 S/cm at a temperature of 350 K. Additionally, it was found that increasing electric field intensity, temperature, and hydration level can enhance the diffusion of water molecules and hydrated protons and improve the proton conductivity of the PEM. Especially, at low electric field intensity, ordered PEM demonstrates superior proton conductivity compared to amorphous PEM. However, as the electric field strength increases to 0.7 V/nm, the proton diffusion behaviour of amorphous PEM gradually surpasses that of ordered PEM. Moreover, the electric field can enhance the anisotropic diffusion behaviour of PEM. As the electric field increases from 0 V/nm to 0.7 V/nm, the diffusion coefficient parallel to the direction of the electric field increases by three orders of magnitude, while the diffusion coefficient perpendicular to the direction of the electric field increases by only one order of magnitude.

Exploring the influence of external electric fields on the mechanical characteristics of zirconium disulfide nanosheets via density functional theory

The density functional theory is utilized to investigate elastic and plastic properties of zirconium disulfide (ZrS2) nanosheet subjected to a uniform external electric field up to 4 VÅ. In this respect, firstly, unit cell dimensions, bond lengths and bond angles are obtained by optimizing the unit cell of ZrS2nanosheet, and the most stable configuration is considered for the nanostructure accordingly. Then, by applying uniaxial and biaxial tensions on the nanosheet under a uniform external electric field, Young's and bulk moduli are computed, respectively. Finally, the applied strain is extended to the plastic region to evaluate the effect of external electric field on the first and second critical strains. It is shown that applying external electric field results in increasing Young's modulus of the nanosheet. However, the bulk modulus increases up to 2 VÅ and deceases afterwards. Besides, the first and second critical strains, which are respectively used to show the end of harmonic and inharmonic regions, decrease in the presence of the external electric field while the difference between them is not affected by the external electric field. Investigating the elastic and plastic properties of zirconium disulfide under an external electric field is important for both fundamental research and practical applications. It can help us develop new materials with tunable properties, optimize their performance in various devices, and contribute to the development of cutting-edge technologies

Effect of external electric field on agglomeration characteristics of Cu nanoparticles: A molecular dynamics study

In order to study the effect of electric field on the stability of Cu nanoparticles in water, molecular dynamics method was used to simulate the agglomeration characteristics of Cu nanoparticles. The microscopic agglomeration characteristics of nanoparticles by electric field were analyzed using the distribution and collision of nanoparticles in water at different times, as well as the potential energy, kinetic energy, diffusion coefficient and radial distribution function of the system. The results show that the collision of Cu nanoparticles was inhibited in the presence of both uniform and alternation electric fields. The total potential energy of the system decreases with each collision of particles. When all of the particles are agglomerated, the total potential energy of the system remains constant. According to the radial distribution function, when the electric field intensity increases, the degree of aggregation of water molecules on the particle surface strengthens and then weakens as the electric field strength. Meanwhile, the degree of aggregation decreases with the increasing frequency of the alternating electric field. The effect of electric field frequency on the diffusion coefficient of nanofluid is insignificant. However, as the strength of the electric field increases the diffusion coefficient of the nanofluid decreases, while the resistance coefficient of water molecules increases, and the presence of the electric field inhibits the movement of water molecules. The influence of electric field on the heat transfer and deposition characteristics of nanofluids can be obtained by experiments, but the influence mechanism is difficult to be analyzed by experimental means. The molecular dynamics method also provides a new idea to reveal the influence mechanism of electric field.

Effects of external electric fields on molecular properties of nitrogen/tetrafluoromethane complex: A density functional theory study

Nitrogen/tetrafluoromethane (N2/CF4) has attracted wide attention for its reliable dielectric performance and potential to be utilized as a coolant and insulator of power apparatus. Several studies have investigated the basic properties of N2/CF4, but dielectric responses of such a mixture under extreme electric fields are not fully understood, primarily on a molecular level. Here, we modeled the N2/CF4 complex and calculated the molecular properties under different external electric fields through computational quantum chemistry methods. Results suggest that the electric-field-induced polarization can be apparently observed in both positive and negative direction cases; the deformed electronic structure leads to an increased dipole moment and a narrowed energy gap. In addition, the molecular vibrational modes are sensitive to external electric fields, resulting in the splitting and shifting of IR spectra. Moreover, the external electric field also affects the excited-state properties of N2/CF4, and the emerged absorption peaks under extreme electric fields were analyzed in detail. These findings provide a better understanding of the N2/CF4 properties under external electric fields and lay a foundation for designing the electrical insulation systems of the power apparatus.

Molecular configuration, electronic properties, reaction activity of metal-free naphthalocyanine under the external electric field

This work presents a regulation effect of external electric fields on geometric structures, polarisability and reaction activity of metal-free naphthalocyanine (H2Nc). In particular, EEF more than 0.015 a.u.(0.77 V/Å) will bend two pairs of opposing molecular arms (naphthalene subunits) to the x-positive and x-negative directions of the planar molecule. Flipping the EEF direction flips also the bending direction of molecular arms. Furthermore, when the EEF is removed, the molecule can be restored to the planar structure. EEF can induce a significant dipole moment transformation (magnitude and direction of the dipole moment), reduce LUMO-HOMO gap of H2Nc, enhance the first hyperpolarizability from 0 to a significant amount, and change the distribution of electrophilic or nucleophilic reaction sites and enhance reactivity of H2Nc. EEF can be used to regulate the structure transformation and properties of H2Nc, which can promote the potential application of H2Nc such as molecular devices or chemical reactions.

Modeling the influence of the external electric fields on water viscosity inside carbon nanotubes.

Equilibrium molecular dynamics simulations were performed to explore the effects of external electric fields and confinement on water properties inside various carbon nanotubes (CNTs). Using different GHz electric field frequencies as well as various constant electric field strengths, the radial distribution function and density profile were investigated, by which the impact of the electric fields and confinement on the water structure are revealed. The results indicated water molecules inside the CNT form layered structures due to topological confinement applying external electric fields can disturb this ordered water molecules structure and increase the viscosity of confined water, particularly in the case of CNTs with a radius less than 13.5Å. Conversely, for CNTs with a radius greater than13.5Å, the viscosity decreases under the influence of external oscillating or constant electric fields. How dose the synergism of confinement and external electric fields affect the water properties inside the CNTs?

Molecular modeling of the structural, electronic, excited state dynamic, and the photovoltaic properties of the oligomers of n-corannulene (n = 1–4)

Despite the fact that n-corannulene oligomers (n = 1–4) have a variety of electronic and optical properties, including the ability to be tuned and the potential to be used as light-harvesting materials, there has not been a computational assessment of their structural, electronic, and optical properties. Herein, a computational evaluation of the concerned materials regarding their potent use in solar cell technology has been conducted via DFT/CAM-B3LYP and M062X/6-311+G level of theory. It was observed that the calculated 1st frequency of the n-Corannulene (n = 1–4) were 144.15, 106.36, 48.96 and 42.21 respectively. Notably, the computed cohesive energy value increased as the number of Corannulene units increases while the electronic characteristics revealed that the chemical activity of the structures increased as the number of oligomers rose. Both calculation techniques demonstrate that the number of n-Corannulene oligomers increases the HOMO energy while decreasing the LUMO energy based on the external electric field (EF) effect. The findings demonstrated that as EF intensity increases, the energy gap (Eg/eV = |EHOMO-ELUMO|) of these molecular systems decreases which can be attributed to a decrease in the electron transfer potential barrier. The 4-Corannulene systems showed the highest wave length of adsorption for the investigated compound at 546.18 nm, with the highest oscillator strength of 0.2708 and the lowest transition energy of 2.2700 eV, arising from S0–S1 (H-L) and the highest major percentage contribution of 93.34 % in comparison to the investigated compounds. We are hopeful that this research will help experimental researchers understand the potential of n-Corannulene, specifically 4-corannulene, as powerful material for a variety of applications ranging from solar cell, photovoltaic properties and many others.

Toward metal- and catalyst-free Reactions: Deciphering the substituent and external electric field effects on the Diels-Alder reaction between ethylene and nitrosoethylene

The substituents on the diene and/or dienophile can contribute to the decrease or increase of this energy. However, there are other approaches to catalyze chemical reactions, particularly Diels-Alder reactions, for example, the application of an electric field along the reaction axis. The existence of an external electric field (EEF), properly oriented, has the potential to further stabilize or destabilize these electron density contributors and thus influence the energy. The goal of this study was to compare the activation energies of the Diels-Alder reaction between ethylene and nitrosoethylene, using an electric field, Lewis acid (BH3) as catalysts, and the influence of substituents. All calculations were performed with Gaussian09 software. The compounds were fully optimized using the restricted Hartree-Fock method with the basis set 6-31G, and single-point energies were determined with the MP3 method and basis set 6-31G. The effects of EEFs were studied using the “Field = M ± N” keyword with F values (F=±0.125 au and ± 0.080 au) along the preferred axis. The lowest activation barrier is encountered when the electric field is applied, followed by the use of borane as the Lewis acid.

Electronic and optical characteristics of Silicane/GeAs van der Waals heterostructures: Effects of external electric field and biaxial strain: A first-principles study

The van der Waals heterostructure offers unusual physical properties to design novel structures for efficient optoelectronic applications. To enhance the low mobility of monolayer SiH and broaden the light absorption coefficient and range of monolayer SiH, a lattice-matched SiH/GeAs vdWh has been constructed. At the same time, the basic electronic and optical properties were investigated by first-principles calculations. The SiH/GeAs vdWh with six different structural configurations were compared, and the most stable configuration model H2 has a type-II band alignment with an indirect bandgap semiconductor value of 1.54 eV. It is associated with a strong charge transfer. Moreover, SiH/GeAs vdWh possesses anisotropic transport properties with high electron mobility along the y-direction. Interestingly, both external electric field and biaxial strain can adjust band offsets and bandgaps values. After applying vertical electric fields, The SiH/GeAs vdWh has a mutual transformation from type-I (symmetric) to type-II(staggered) to type-III(broken) band alignment, and metal-semiconductor phase transitions occurred at −0.35 and 0.15 V/Å. Besides, it's found that band alignment transition from type-II to type-I emerged under the in-plane biaxial strain of 2% and transformed indirect into direct bandgap. More importantly, tensile biaxial strain can enhance the visible-light absorption while sustaining type-II band alignment, which is favorable for photocatalysis of visible light. Our results indicate that the SiH/GeAs vdWh's moderate bandgap, excellent transport properties and optical performance may have potential applications in the field of nanoelectronic and optoelectronic devices.

The effects of external electric field and additional strain on electronic and magnetic properties of CrI3/SnC heterostructure

The electronic properties of CrI3/SnC heterostructure are investigated by the first-principles method. The Curie temperature (Tc) of CrI3/SnC heterostructure (57.1 K) is higher than that of monolayer CrI3 (∼45 K) significantly, and the nonmagnetic SnC monolayer is also magnetized. CrI3/SnC heterostructure shows an intrinsic type-II band alignment with the band gap (Eg) of 0.34 eV, which facilitates the separation of photogenerated electrons and holes in photoelectric devices. Applying strain and electric field (Eext) can effectively tune the electronic properties of the heterostructure. The transition from semiconductor to metal can be observed when applying greater horizontal strain or stronger Eext. The highest Tc can reach 89.4 K and 207.2 K by applying vertical compressive strain and horizontal uniaxial compressive strain, respectively. The half-metal feature can be realized when Eext = −0.8 V/nm. These findings suggest a new possibility for developing magnetic heterostructure devices.