Insights on cholinium- and piperazinium-based ionic liquids under external electric fields: A molecular dynamics study

Effect of static external electric field on bulk and interfaces in organic solar cell systems: A density-functional-theory-based study

Phosphorene and graphene flakes under the effect of external electric field as an anode material for high-performance lithium-ion batteries: A first-principles study

Using the density functional B3P86/cc-PV5Z method, the geometric struc- ture of AlH molecule under different external electric fields are optimized, and the bond lengths, dipole moments, vibration frequencies and other physical properties parameters are obtained. The potential energy curves under different external fields are also obtained by CCSD(T) method with the same basis set. These results show that the properties parameters and potential energy curves may change with different external electric field, especially in the reverse electric fields. The potential energy function without external electric field is fitted by Morse potential, and the poten- tial energy curves under different external fields are fitted using constructed potential model, which adopted the dipole approximation theory. It is found that the fitting parameters are good agreement with experimental values and the critical dissociation electric parameter is consistent with numerical calculation. These results will provide important theoretical and experimental reference for further studying the molecular spectrum, dynamics and molecular cooling with Stark effect.

The effects of a static external electric field on the ground state electronic structure of a porphine-quinone (PQ) complex have been studied by using density functional theory (DFT). The energies of the excited states have been calculated with time-dependent density functional theory (TDDFT) and with the approximate coupled cluster singles and doubles (CC2) method. The geometries of porphine and quinone have been optimized with B3LYP. The influence of the external electric field on the PQ complex has been studied at six different intermolecular distances between 2.5 and 5.0 Å with the BH&HLYP functional. An external electric field clearly affects the orbitals localized mostly on quinone but not the orbitals localized on porphine. Additionally, the effect of the external field increases with the increasing intermolecular distance. The optical absorption spectrum of porphine obtained by using the BH&HLYP functional is consistent with the Gouterman model and with the spectrum previously calculated with CAM-B3LYP. The potential energy curves of the Q and B states and the lowest charge transfer (CT) states of the PQ complex calculated by using the BH&HLYP with TDDFT functional have also been compared with those obtained with the CC2 method. Both methods show that the lowest CT state is clearly above the Q states when no external field is applied. Therefore, when the Q states of a porphine-quinone system are excited, the conical intersection is not possible and cannot thus provide a path for electron transfer (ET). The calculations show that the Q and B states are affected by the field much less than the lowest CT state. Consequently, the calculations show that the CT state crosses the Q and B states at certain field strengths. Thus, it is possible that the external electric field triggers ET in porphine-quinone systems via conical intersection.

Study on regulation effect of external electric field on energetic material 1-methyl-2,4,5-Trinitroimidazole

To reveal the biochemical mechanism of pyruvic acid under the bioelectric currents, the effect of the external electric field on the intermolecular double-proton cooperativity migration was investigated for the dimer, accompanied by a comparison of the conformation transformation. The results indicate that the influences of the external electric fields on the transition state of the proton migration, i.e., the changes in the molecular structures, atoms in molecules, surface electrostatic potentials, and potential barriers, are closely related to the directions of the fields. The spatial order parameters of the conformation transformation of pyruvic acid can be quickly converged through the umbrella sampling and parameter averaging, thereby obtaining the potential energy surface of the potential of mean force. Under the strong external electric field, the barrier heights of the double-proton cooperativity migration are close to the free energy change of the conformation transformation, indicating the competition between the proton cooperativity transfer and conformation transformation. This study is of importance for revealing furthermore the essence of the competition between the proton migration and conformation transformation of the biomolecules stimulated by the bioelectric currents. The effects of external electric fields on the double-proton cooperativity migration reaction pathway, potential barrier, and rate constant of the pyruvic acid dimer were studied using the M06-2X/6-311++G**, M06-2X/aug-cc-pVTZ, and CCSD(T)/6-311++G(2d,p) methods by using Gaussian 09 packages. A chaotic finite temperature string model with enhanced sampling for molecular conformation transformation was constructed, and the free energy change of conformation transformation under external electric field was studied by the finite temperature string (FTS) method with the CHARMM22 force field from NAMD software packages and PLUMED program.

Energy dispersion and electron g-factor of quantum wire in external electric and magnetic fields with Rashba spin orbit interaction

In the absence of an external electric field, it has already been known that ion clusters are formed instantaneously in moderately concentrated ionic solutions. In this work, we use molecular dynamics (MD) simulations to investigate the changes of structural, dynamic, and transport properties in a sodium chloride solution under an external electric field from the ion cluster perspective. Our MD simulation results indicate that, with a strong external electric field E (≥0.1 V/nm) applied, ion clusters become smaller and less net charged, and the structures and dynamics as well as transport properties of the ion solution become anisotropic. The influence of the cluster structure and shell structure to transport properties was analyzed and the Einstein relation was found invalid in this system.

Effects of external electric and magnetic fields on the linear and nonlinear optical properties of InAs cylindrical quantum dot with modified Pöschl-Teller and Morse confinement potentials

External electric field effects on absorption, fluorescence, and phosphorescence spectra of a series of unsubstituted diphenylpolyynes have been examined in a PMMA film. The analysis of the electroabsorption spectra indicates that the shorter diphenylpolyynes exhibit only the change in molecular polarizability, whereas the longer ones exhibit the change both in dipole moment and in molecular polarizability following absorption. The finding of the change in dipole moment following absorption of centrosymmetric diphenylpolyynes is interpreted in terms of the symmetry distortion upon doping a polymer film. When the external electric field is applied, the fluorescence yield is reduced and enhanced, respectively, in diphenylacetylene and diphenyloctatetrayne, indicating that the rate of the nonradiative process from the fluorescence state is accelerated in diphenylacetylene and decelerated in diphenyloctatetrayne by an external electric field. All of the diphenylpolyynes used in the present study exhibit the change in molecular polarizability following the phosphorescence process.

The influence of environments (THF solvents and electric field) and molecular self-aggregations on the structure and optical properties of 4-(4-hydroxyphenylazo)nitrobenzene has been investigated by molecular dynamics (MD) simulations and quantum chemical calculations. Long-range electrostatic effects and the hydrogen bond interactions between the solute and the THF solvent molecules lead to the augments of nonlinear optical (NLO) response by about two times from the gas phase to THF solution, accompanied by considerable red-shift of more than 40 nm in the maximum absorption wavelengths of the ground (S(0)) and low-lying excited states (S(1), S(2), and S(3)). The solvated chromophore reorients quickly (within 300 ps) under external electric field of 1.0 V/nm, even when the direction of the applied electric field is antiparallel to the dipole moment of the solute. Nonequilibrium MD simulations demonstrate that the light-induced cis-trans isomerization in THF solution and external electric field need longer relaxation time (about 1.0 ps) than that in gas phase (about 500 fs). The dipole-dipole interactions and intermolecular hydrogen bonds facilitate the self-aggregations of solute molecules in solution. The V-shaped dimer exhibits higher hyperpolarizability value by about 1.2 times of the monomer, whereas the antiparallel alignment leads to a cancellation of dipole moment and hence dramatic decrease in hyperpolarizability (one-third of the monomer). However, the Boltzmann-weighted contribution to hyperpolarizability from these two aggregations (with 82% V-shaped and 18% antiparallel) is close to that of the monomer. Orientations of D-π-A dipoles in various environments and molecular aggregations are important to modulate the optical properties of materials.

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 recent discovery of borospherene B40 marks the onset of a new class of all-boron fullerenes. External electric field can influence the structure and property of molecule. It is necessary to understand the electrostatic field effect in the borospherene B40. In this work, density functional theory method at the PBE0 level with the 6-31G* basis set is used to investigate the ground state structures, mulliken atomic charges, the highest occupied molecular orbital (HOMO) energy levels, the lowest unoccupied molecular orbital (LUMO) energy levels, energy gaps, electric dipole moments, infrared spectra and Raman spectra of borospherene B40 under the external electric field within the range of values F=0-0.06 a.u.. The electronic spectra (the first 18 excited states contain excited energies, excited wavelengths and oscillator strengths) of borospherene B40 are calculated by the time-dependent density functional theory method (TD-PBE0) with the 6-31G* basis set under the same external electric field. The results show that borospherene B40 can be elongated in the direction of electric field and B40 molecule is polarized under the external electric field. Meanwhile, the addition of external electric field results in lower symmetry (C2v), however, electronic state of borospherene B40 is not changed under the external electric field. Moreover, the calculated results show that the electric dipole moment is proved to be increasing with the increase of the external field intensity, but the total energy and energy gap are proved to decrease with the increase of external field intensity. The addition of external electric field can modify the infrared and Raman spectra, such as the shift of vibrational frequency and the strengthening of infrared and Raman peaks. Furthermore, the calculated results indicate that the external electric field has a significant effect on the electronic spectrum of borospherene B40. The increase of the electric field intensity can lead to the redshift of electronic spectrum. With the change of the electric field intensity, the strongest excited state (with the biggest oscillator strength) can become very weak (with the small oscillator strength) or optically inactive (with the oscillator strength of zero). Meanwhile, the weak excited state can become the strongest excited state by the external field. The ground state properties and spectral properties of borospherene B40 can be modified by the external electric field. Our findings can provide theoretical guidance for the application of borospherene B40 in the future.

As a follow-up to our investigation into the effect of external electric field on the chemical bond strength, the effects of external electric field on the CH3NO2 → CH3ONO isomerization dynamics were investigated using the MP2/6-311++G(2d,p) and CCSD/6-311++G(2d,p) methods. The rate constants in the absence and presence of various field strengths were calculated. The results show that, when the field strength is larger than +0.0060a.u. along the C-NO2 bond axis, the barriers of the isomerization are lower than the C-NO2 bond dissociation energies, leading to the preferences of the isomerization over the C-NO2 bond dissociation. In this case, the sensitivities are higher than that in no field. However, in the other fields, the C-NO2 bond scission is favored and the sensitivities are almost equal to that in no field. Several good linear correlations are found between the field strengths and the changes of the bond lengths or corresponding electron densities.

The effects of external electric fields (EFs) on the magnetic state and substrate-mediated magnetic coupling between Mn dimers on Cu(1 1 1) have been studied using a first-principles theoretical method. The calculations show that a change in the ground-state magnetic order, from antiferromagnetic (AF) to ferromagnetic (FM), can be induced within an isolated Mn2 on Cu(1 1 1) by applying a moderately strong EF of about 1 V Å−1. The magnetic exchange coupling between pairs of dimers displays Ruderman–Kittel–Kasuya–Yosida-like oscillations as a function of the interdimer distance, which depend significantly on the magnetic order within the dimers (FM or AF) and on their relative orientation on the surface. Moreover, it is observed that applying EFs allows modulation of the exchange coupling within and between the clusters as a function of the intercluster distance. At short distances, AF order within the dimers is favoured even in the presence of EFs, while for large distances the EF can induce a FM order. EFs pointing outwards and inwards with respect to the surface favour parallel and antiparallel magnetic alignment between the dimers, resspectively. The dependence of the substrate-mediated interaction on the magnetic state of Mn2 is qualitatively interpreted in terms of the differences in the scattering of spin-polarized surface electrons.