Influence Of External Electric Field Research Articles

外电场对MMTD分子结构与电子光谱影响的研究

外电场对MMTD分子结构与电子光谱影响的研究

Effect of External Electric Field upon Lower Alkanols

Applying the Monte Carlo method, molecules of methanol, ethanol and 1-butanol are brought to temperature of 300 K and under the influence of external electric field of 0.01 a.u their electronic spectra are simulated with HyperChem 8.0 involving ZINDO/S semiempirical method. Particular molecules differently react to the electric field applied as shown by the electronic spectra simulated in the range of 250-2.84 nm. Total energy of the methanol and ethanol molecules turn slightly more negative in the electric field whereas that energy found for 1-butanol more significantly turn to less negative. HyperChem 8.0 software is used together with the AM1 method for optimization of the conformation of the molecules of methanol, ethanol, 1-propanol and 1-butanol. Then polarizability, charge distribution, potential and dipole moment for molecules placed in the external electric field of 0.000, 0.001, 0.01 and 0.05 a.u. are calculated. External field induces a slightly field strength dependent polarizability of the molecules and the electron density redistribution at particular atoms. Total dipole moment (DM) for particular alkanols increases with the strength of the field applied. There is particularly sharp increase in DM at 0.05 a.u. field. Key words: Butanol; Computer simulations; Ethanol; Methanol; Propanol

A Reflective Display Technology Based on Electrofluidics

In this paper we describe the design, driving and electro-optical behavior of an electrofluidic, or electrowetting, display panel. Electrofluidic displays involve the movement of a colored oil water interface as a result of polarizing the interface between water and a hydrophobic surface under the influence of external electric field. The proposed direct-segment drive approach successfully drives the display panel based on electrofluidic. The electro-optical behavior of electrofluidic display samples are measured and analyzed. The tonand toffof the pixel is 16 ms and 8 ms, respectively, which demonstrates that electrofluidic display panels have the capability to show video content.

BNNTs under the influence of external electric field as potential new drug delivery vehicle of Glu, Lys, Gly and Ser amino acids: A first-principles study

The interaction of Glu (Glutamic acid), Lys (Lysine), Gly (Glycine) and Ser (Serine) amino acids with different polarities and (9, 0) zigzag single-wall boron nitride nanotubes (BNNTs) with various lengths in the presence and absence of external electric field (EF) in gas and solvent phases, are studied using density functional theory. It is found that interaction of Glu, Lys, Gly and Ser amino acids with BNNTs in both phases is energetically favorable. From solvation energy calculations, it can be seen that the BNNTs/amino acid complex dissolution in water is spontaneous. The adsorption energies and quantum molecular descriptors changed in the presence of external EF. Therefore, the study of BNNTs/amino acid complex under influence of external electric field is very important in proposing or designing new drug delivery systems in the presence of external EF. Results indicate that Glu, Lys, Gly and Ser amino acids can be adsorbed considerably on the BNNTs in the existence of external electric field. Our results showed that the BNNTs can act as a suitable drug delivery vehicle of Glu, Lys, Gly and Ser amino acids within biological systems and strength of adsorption and rate of drug release can be controlled by the external EF.

Influence of external electric fields on oxygen vacancies at the anatase (101) surface.

Understanding how defects in solids interact with external electric fields is important for technological applications such as memristor devices. Using Density Functional Theory (DFT) calculations, we have studied the influence of an external electric field on the formation energies and diffusion barriers of surface and subsurface oxygen vacancies at the (101) surface of anatase TiO2. DFT in the generalized gradient approximation as well as DFT+U methods with different U values have been utilized, with the electric field treated self-consistently by adding a sawtooth-like potential to the bare ionic potential. Our results show that the direction and strength of the applied field can have a significant influence on the relative stabilities of surface and subsurface defects, whereas the effect on the subsurface-to-surface defect migration is found to be relatively minor.

In-vitro bipolar nano- and microsecond electro-pulse bursts for irreversible electroporation therapies

Under the influence of external electric fields, cells experience a rapid potential buildup across the cell membrane. Above a critical threshold of electric field strength, permanent cell damage can occur, resulting in cell death. Typical investigations of electroporation effects focus on two distinct regimes. The first uses sub-microsecond duration, high field strength pulses while the second uses longer (50μs+) duration, but lower field strength pulses. Here we investigate the effects of pulses between these two extremes. The charging behavior of the cell membrane and nuclear envelope is evaluated numerically in response to bipolar pulses between 250ns and 50μs. Typical irreversible electroporation protocols expose cells to 90 monopolar pulses, each 100μs in duration with a 1second inter-pulse delay. Here, we replace each monopolar waveform with a burst of alternating polarity pulses, while keeping the total energized time (100μs), burst number (80), and inter-burst delay (1s) the same. We show that these bursts result in instantaneous and delayed cell death mechanisms and that there exists an inverse relationship between pulse-width and toxicity despite the delivery of equal quantities of energy. At 1500V/cm only treatments with bursts containing 50μs pulses (2×) resulted in viability below 10%. At 4000V/cm, bursts with 1μs (100×), 2μs (50×), 5μs (20×), 10μs (10×), and 50μs (2×) duration pulses reduced viability below 10% while bursts with 500ns (200×) and 250ns (400×) pulses resulted in viabilities of 31% and 92%, respectively.

Preparation of PVDF UF Membranes under an External Electric Field with PVP as Additive

In this study, PVDF UF membranes were prepared with PVP as additive via a favorable method of applying high voltage external electric field (2kV) through the immersion precipitation phase inversion process. The influence of external electric field on the structure, surface functional groups, membrane potential, and surface hydrophilicity of the membranes were researched. In addition, anti-fouling property and separation performance of the membranes were also investigated. The results indicated that the protein adsorption amount on the electric treated membranes was distinctly reduced. Especially for the electric treated PVDF membrane with PVP K70 as additive, the value of water contact angle reached 75.4° and the protein adsorption amount decreased 76 %, reaching 20.39 µg·cm-2. The separation performance of the electric treated membrane was also superior to that of the un-treated membrane. All the experimental results indicated that this electric treated approach open a promising way for the modification of PVDF membrane because it combined membrane preparation and modification in only one physical step without additional chemical reagents.

Spin dephasing in organic semiconductor spintronic devices

A theoretical model to study spin dephasing for materials with weak spin orbit coupling is developed in this work. It considers the contributions from not only the drift current but also the diffusion part, which pronouncedly enlarges the application scope of the model. The spin lifetime in spin drift diffusion equation is also corrected by considering the thermal effect and the influence of external electrical field. The spin lifetime corrected by this model agrees well with the experimental data. It is found that under the same voltage bias the spin coherence are much more pronounced in the organic semiconductors (OS) than in Si due to the fact that the applied electrical field affects only part of charge carriers polarons in OS, and a continuous spin transport could be achieved in a larger scale.

Propagation through complex structured liquid crystal optical fibers

Wave propagation in optical mediums greatly depends on the materials of which the guides are composed. Among the other forms of optical mediums, liquid crystals are both inhomogeneous and optically anisotropic in nature, and exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electrical fields. These features make optical fibers containing liquid crystals greatly useful for fabricating many optical devices for practical applications. As such, the analytical investigation of wave propagation through liquid crystal optical fibers, particularly a three-layer fiber with radially anisotropic liquid crystal material in the outermost clad section, remains interesting. The power confinement in the liquid crystal section of such fibers can be enhanced for these to be efficiently used in optical coupling and/or sensing applications. Furthermore, a control over the dispersion characteristics, and, hence, the confinement of power, in such fibers may be imposed by making the guide even more complex in the form of introducing a conducting sheath helix structure at the core-inner clad interface.

Spin–orbit interaction effect on nonlinear optical rectification of quantum wire in the presence of electric and magnetic fields

Here we have investigated the influence of external electric field and magnetic field on the nonlinear optical rectification of a parabolic confinement wire in the presence of Rashba spin–orbit interaction. We have used density matrix formulation for obtaining optical properties within the effective mass approximation. The results are presented as a function of quantum wire radius, electric field, magnetic field, Rashba spin–orbit interaction strength and photon energy. Our results indicate an increase of electric field gives the red-shift of the peak positions of nonlinear optical rectification. The role of confinement strength and spin–orbit interaction strength as control parameters on this nonlinear property have been demonstrated.

First-principles study of electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate

The electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate have been studied using density functional theory. The results indicate that the influence of external electric field on the crystal structure is anisotropic. The electric field effects on the distance of the Pb-O ionic interactions are stronger than those on the covalent interactions. However, the changes of most structural parameters are not monotonically dependent on the increased electric field. This reveals that lead styphnate can undergo a phase transition upon the external electric field. When the applied field is increased to 0.003 a.u., the effective band gap and total density of states vary evidently. And the Franz-Keldysh effect yields larger influence on the band gap than the structural change induced by external electric field. Furthermore, lead styphnate has different initial decomposition reactions in the presence and absence of the electric field. Finally, we find that its sensitivity becomes more and more sensitive with the increasing electric field.

Molecular structure and excited states for BN under strong electric field

The ground states of BN molecule under different strong electric fields ranging from -0.06 a.u. to 0.06 a.u. are optimized using density functional method B3LYP at 6-311++g(d.p) level. Optimized parameters, dipole moment, charge distribution. HOMO energy, LUMO energy, energy gaps, infrared spectrum are obtained. The result shows that with the increasing of the external electric field, the correlation between molecular structure parameters and the electric field intensity becomes obvious and presents the asymmetry. In addition, TDDFT method at the same level is used to study the influence of external electric field on BN molecular excitation energy and oscillator strength, and the result shows that the electron transition spectrum is blue-shifted with the increase of the external electric field, but the intensity of the vibrator has a more complicated change, showing that the spectral intensity is affected by the electric field.

Molecular structure and properties of zirconiumdioxide under the external electric field

In order to study the influence of external electric field on ZrO2, molecular structure of ZrO2 ground state is optimized by density functional theory (B3P86) method with 6-311++G* basis sets for O atom and aug-cc-pVTZ-PP for Zr atom. The effects of electric field ranging from 0 to 0.025 a.u. are investigated on bond length, total energy, charge distribution, dipole moment, HOMO (the highest occupied molecular orbital) energy level, LUMO (the lowest unoccupied molecular orbital) energy level and energy gap. The excitation energies, transition wavelengths and oscillator strengths under the same intense external electric fields are calculated by the time dependent density functional theory (TD-B3P86) method. The result shows that the bond length of Zr-2O and total energy increase with external field increasing, but the bond lengths of Zr-3O, LUMOs and energy gaps decrease, and HOMOs almost keep the same. The excitation energies decrease and the transition wavelengths of the six excited states are red shifted toward longer wavelength as the applied electric field increases. Therefore the spectral region of zirconiumdioxide molecule can be expanded in visible-infrared region by the use of external electric fields.

Electric field effect on the electronic properties of double-walled carbon-doped boron-nitride nanotubes

Carbon (C) doped zigzag (8, 0)@(16, 0) and armchair (5, 5)@(10, 10) double-walled boron-nitride nanotubes (DWBNNTs), under the influence of external electric fields applied in different directions are studied through first-principles calculations. We have considered the substitution of a B and a N (one species at each wall—inner or outer) by C atoms, generating a type-n inside a type-p semiconductor ((type-n)@(type-p)) and vice-versa. The resulting doped DWBNNT can be thought as a p–n junction. The obtained formation energies and structural properties results indicate that these structures present good stability and are not affected by the electric field application. For the electronic structure, it was observed that external fields can be used to modulate these systems energy gaps. Also, there is a preferred field direction which minimizes the gap values, and the gap increase or decrease is related to the reverse and direct polarization of the p–n junction, respectively.

Excitonic effects of bilayer graphene: A simple approach

The present work investigates the excitonic effects on the bilayer graphene with layers of different thickness under the influence of external electric field through a simple numerical approach. The band structure and energy gap have been calculated using a tight-binding model including parameters like the second-nearest-neighbor-hopping energies t′ (in-plane) and γ (intra-layer) and the on-site energy Δ, in details. The binding energy of exciton for bilayer graphene has been calculated by Wannier model and Hartree–Fock approximation through the Bethe–Salpeter equation. Finally the optical conductivity spectrum of bilayer graphene has been calculated by using the effective mass approximation in two band model.

Spin–orbit interaction effect on the linear and nonlinear properties of quantum wire in the presence of electric and magnetic fields

Here we have investigated the influence of external electric field and magnetic field on the optical absorption and refractive index changes of a parabolically confinement wire in the presence of Rashba spin orbit interaction. We have used density matrix formulation for obtaining optical properties within the effective mass approximation. The results are presented as a function of quantum wire radius, electric field, magnetic field, Rashba spin orbit interaction strength and photon energy. Our results indicate an increase of electric field redshifts the peak positions of absorption coefficient and refractive index changes. The role of confinement strength and spin orbit interaction strength as control parameters on the linear and nonlinear properties have been demonstrated.

Raman investigation of electric field induced molecular modifications in organic field effect transistors

The influence of external electric fields on the vibrational properties of Pentacene-based field effect transistors were investigated by Ramanspectroscopy.ThemonitoredRamanbandswereintherangefrom 1100cm−1 to1200cm−1,whereabroadbandispresentandenhanceddue to the external electric field. The process is modeled by density functional theory (DFT) at the B3LYP/3–21G level. Additionally, the relaxation of the Raman bands after the removal of the external field was determined from an exponential Debye like decay fitting to be approximately 94 min, this finding indicates that a long relaxation time ca. 8 h is required in order to recover the original structure. Experimentally and theoretically was demonstrated that the applied electric fields induce artificial traps in the organic layer mediated by charge carrier–dipole interaction.

Theoretical study of reorientation and torque of liquid crystal molecules under influence of external electric field and experimentally generation of spatial optical soliton beam and getting a sharp switching in chiral nematic liquid crystal

Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed.

Influence of external electric field on copper slag cleaning process

Ionic structures of the molten copper slags indicated the possibilities of utilisation of electrocapillary phenomenon in accelerating the setting of copper drops from the slag, and the slag electrolysis in reduction of magnetite and precipitation of the dissolved copper. The behaviours of molten copper slag under the electric field were investigated in this paper. The presence of a certain electric field could accelerate the migration of copper drops from anode to cathode to improve the copper slag cleaning. The effects of some major factors, such as electric field strength, experimental temperature (ET) and copper slag cleaning time, were studied. The slag cleaning was promoted with the increasing electric field strength and ET, but the cleaning rate was decreased with the passage of sedimentation time. The electrolysis of molten slag was also mentioned.

Influence of external electric field on the molecular structure and electronic spectrum of paranitrochlorobenzene

In order to achieve the goal of degenerating organic pollutant nitrochlorobenzene, the influence of electric field on molecular structure and electronic spectrum and so on is studied by applying an external parallel electric field. Take paranitrochlorobenzene as a study object, the method B3LYP of the density functional theory at 6-311+g(d, p) level is used to calculate its molecucar structure, dipole moments and total energies of the ground state under different external electric fields (from 0 to 0.025 a.u.) in this paper. On this basis, the time-dependent density functional theory is used to study the influences of external electric field on excited wavelength and oscillator strength of the first six excited states. The results show that bond lengths (C–Cl, C–N) increase rapidly and bond energy decrease rapidly with the increase of field intensity. At the same time, bond length (C–C, C–H) changes of benzene ring are very small, and the increases or decreases are not uniform. This illustrates that molecular degradation may lead to the fractures of bonds (C–Cl, C–N), and the benzene ring is relatively stable. what is more, the molecular total energy first increases then decreases, and the dipole moment first decreases then increases with the increase of the field intensity. In addition , the maximum absorption wavelength first slowly decreases, and then increases rapidly with the increase of the field intensity, which causes the electron transition to be relatively easy, while oscillator strength changes relatively complex in anner.