Magnitude Of External Electric Field Research Articles

Influence of external electric field on molecular microscopic descriptors of non-polar insulating gases

Molecular microscopic descriptors without external electric field are commonly used for the prediction of insulating strength in gaseous medium. However, insulating gases are subjected to external electric field in electrical equipment, and the molecular microscopic descriptors are affected. Therefore, it is necessary to investigate the influence of external electric field on molecular microscopic descriptors. The Gaussian 16 software is employed to calculate the global parameter with the M06-2X functional and the 6–311++G (d, p) basis set. The wavefunction analysis software Multiwfn is used to obtain electrostatic potential parameter. In this paper, three directions of external electric field with magnitude ranging from 0 to 0.03 a.u. have been set to 10 non-polar insulating gas molecules. According to the type of molecular point group, the effect of direction and magnitude of external electric field on the molecular microscopic descriptors has been analyzed. The results indicate that the molecular microscopic descriptors are affected by the direction and magnitude of external electric field. The change rate of microscopic descriptors increases with the increase of external electric field magnitude. And the influence of the direction of external electric field is associated with the molecular symmetry. In conclusion, the effect of direction and magnitude of external electric field is needed to be considered when analyzing the effect of external electric field on molecular microscopic descriptors.

Influence of Twist-Angle and Concentration Disorder on the Density of Electronic States of Twisted Graphene

In this paper, we present an approach that makes it possible to describe, from unified physical considerations, the influence of rotation-angle and concentration disorder on the density of electronic states of two-layer twisted graphene. The electron relaxation time and the density of electronic states near the Fermi level are calculated by considering the multiple elastic scattering of electrons by impurities and structural inhomogeneities of the short-range order type. An analysis is presented of the change in the contributions to the density of electronic states from electron scattering on foreign atoms with variations in the defectiveness of the structure, impurity concentration, temperature, and the external electric field magnitude. It is shown that the formation of short-range order areas by foreign atoms in the first coordination sphere relative to the surface of the material can lead to the opening of a gap in the density of electronic states of twisted graphene. Point defects and short-range order regions formed by foreign atoms in the second coordination sphere lead to metallization of twisted graphene.

Quenching effect of upper laser level lifetime of Fe2+ ions in ZnSe by free electrons

We theoretically and experimentally examined the assumption that the lifetime excited state of Fe2+ in ZnSe:Fe crystal is quenched by free electrons. The effect of the electron beam current value on the temporal characteristics of the luminescence was studied. Three variants, including a sample in the electronic circuit in the case of Fe2+ ions luminescence excitation in a ZnSe:Fe crystal by a beam of accelerated electrons, were first considered theoretically. These variants differ in external electric field magnitude in the sample, which affects the concentration of free electrons in the excited region of the sample. Equations describing the time dependence of the sample's electron density were derived. The luminescence decay kinetics of Fe2+ ions in ZnSe:Fe crystal excited by electron pulse with different electron beam current values and short-pulse optical radiation were obtained. The values of the quantities that determine the temporal characteristics of the luminescence decay depending on the electron beam current were found.

Electro-optic effect of graded-pitch chiral photonic structures under oblique illumination

We studied theoretically optical spectra when circularly polarized light obliquely impinges on a slab of a chiral photonic structure with linearly and uniformly spatial varying pitch. The material that we considered locally has a $\overline{4}2m$ point-group symmetry and presents Pockels effect, hence, we controlled optical spectra by a low frequency (DC) electric field applied along the nonhomogeneity axis. The spectra display a Bragg-type broadband, where the edge wavelengths of the photonic band are expressed in terms of the medium parameters and the external electric-field magnitude. This allows us to select the region of the electromagnetic spectrum, where the band could become as broad as we choose. We studied three samples with iridescent, silver, and golden colors due to their reflection properties. We observed an enhancement as well as a broadening of the optical band by the application of the electric field. We found that, under certain conditions, when the optical band is practically absent, a very broad band could be created (comparable to the whole visible spectrum) when a DC electric field is applied. This is the result of electro-optic contributions in the permittivity tensor elements, which give rise to a tremendous increase in both the rotatory power and dichroism. Therefore, these media could be used as electrically controlled broadband frequency and polarization filters. Moreover, we observed the usual blueshift of the band as the incidence angle of light increases and an asymmetry in the reflection band amplitude as the incidence angle of the light increases, depending on whether the pitch increases or decreases and the pitch gradient; which endows the sample with different reflection colors for different gradients and incidence angles of the light. The asymmetry in the reflection band vanishes as the magnitude of the electric field increases.

The Electric Field and Microchannel Type Effects on H2O/Fe3O4 Nanofluid Boiling Process: Molecular Dynamics Study

In this computational research, we study the electric field and microchannel type effects on H2O/Fe3O4 nanofluid dynamical manner. The dynamical characteristics of this atomic structure are calculated using molecular dynamics method and we reported physical parameters such as total temperature, total energy, radial distribution function, velocity, density and temperature profiles of H2O/Fe3O4 nanofluid with 2 spherical nanoparticles. Physically, inserting external electric field causes phase transition (boiling process) in H2O/Fe3O4 nanofluid in shorter simulation time. Further, our results show that magnitude of external electric field is a significant parameter in nanofluid dynamical manner in microchannels. By external electric field magnitude increasing, the highest rate of velocity, temperature and density of nanofluid enhance to 0.0071 A·ps−1, 714 K and 0.038 atom·A−3 rates, numerically. Further, by microchannel atomic type variation from Pt to Au one, the rate of temperature and velocity of nanofluids reach to maximum rate at Au microchannel. So we conclude that phase transition of nanofluid in Au microchannel occurs in shorter MD simulation time.

A DFT study on the elastic and plastic properties of MoS2 nanosheet subjected to external electric field

Molybdenum disulfide (MoS2) may be synthesized in a large variety of forms such as particles, monolayer and multilayers nanosheets/nanotubes, ropes and ribbons. Due to such diversity, several applications can be found for MoS2. In this paper, on the basis of density functional theory (DFT) calculations using the generalized gradient approximation (GGA) with the Perdew− Burke−Ernzerhof (PBE) exchange correlation, the elastic properties including Young's and bulk moduli together with plastic properties of MoS2 nanosheet under external electric field with magnitudes within the range of 0 V/ang–1.5 V/ang are determined. It is demonstrated that up to the magnitude of 1 V/ang, the external electric field has a negligible influence on the bulk modulus of MoS2 nanosheet. However, by applying an external electric field equal to 1.3 V/ang, a significant increase in the value of bulk modulus occurs. Additionally, by applying an external electric field equal to 1.5 V/ang, the bulk modulus decreases suddenly, showing the considerable influence of high external electric field on the bulk modulus of MoS2 nanosheet. Also, it is observed that the first and second critical strains of the MoS2 nanosheet subjected to biaxial strain are smaller than those of the MoS2 nanosheet under uniaxial strain. Furthermore, it is revealed that for the both uniaxial and biaxial loading cases, by increasing the magnitude of external electric field, the stability of MoS2 nanosheet decreases.

Ferroelectric field effect of the bulk heterojunction in polymer solar cells

A ferroelectric field effect in the bulk heterojunction was found when an external electric field (EEF) was applied on the active layer of polymer solar cells (PSCs) during the annealing process of the active layer spin-coated with poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester. For one direction field, the short circuit current density of PSCs was improved from 7.2 to 8.0 mA/cm2, the power conversion efficiency increased from 2.4% to 2.8%, and the incident photon-to-current conversion efficiency increased from 42% to 49% corresponding to the different EEF magnitude. For an opposite direction field, the applied EEF brought a minus effect on the performance mentioned above. EEF treatment can orientate molecular ordering of the polymer, and change the morphology of the active layer. The authors suggest a explanation that the ferroelectric field has been built in the active layer, and therefore it plays a key role in PSCs system. A needle-like surface morphology of the active film was also discussed.

Shape Effect on Dielectric and Piezoelectric Properties in Multilayer Actuator

This study presents the piezoelectric and dielectric properties of multilayer actuator, being designed to stack ceramic and electrode layers alternatively, under a consideration of structure geometry, the thickness ratio of the ceramic layer to electrode layer. Increases in polarization and electric field-displacement with increasing thickness ratio of the ceramic/electrode layer were attributed to the change of non-180°/180° domain, ratio of which was affected by the internal stress. The piezoelectricity and actuation behaviors were found to be affected by the volume ratio (or thickness ratio) of ceramic layer relative to ceramic layer as well as the magnitude of external electric field.