Electrostatic Parameters Research Articles

Electrostatic Properties of Selected Personal Protective Equipment Regarding Explosion Hazard

In industries such as the mining, petrochemistry or power industries, personal protective equipment is often used in explosive atmospheres. What causes the occurrence of explosive hazards is ever-present in the work environment they include, electrostatic phenomena as well as the build-up of electrical charges on the surface of the protective equipment used. This paper presents the results of studies which were aimed at determining the fundamental electrostatic parameters of protective helmets as well as eye and face protection, surface resistance and the voltage of electrostatic fields. Examinations on the typical structure of the above mentioned equipment was conducted including the variable values of ambient humidity, which can occur in the working environment and with the use of various types of materials used to generate a charge. The adopted methods and testing equipment have been presented. Using the current, general requirements regarding the electrostatic properties of materials, the examined helmets and eye protection were assessed for their use in explosive atmospheres.

Study of electrostatic parameters of aqueous suspensions for solving the tasks of water treatment and selection of optimal filter media

Relevance of research. At present, there is a need for a comprehensive study of both physical and chemical parameters of substances, which is the primary source of deteriorating treated water quality, as well as the relevant physical properties of the actual filter media to determine the mechanism of their interaction. Such a parameter of purified water as turbidity is closely related to the electrostatic properties of the colloids contained in water. For a more detailed experimental study of this interaction, an operating water treatment facility was chosen. A preliminary study of the conditions at the Communal Enterprise "Chernivtsivodokanal" in the city of Chernivtsi, Ukraine made it possible to identify the typical problems that need to be immediately addressed. The study revealed that the main indicator that is critical for the purification of these waters is turbidity, and one of the main growing concerns to be addressed is the replacement of the filter media.
 Research results. To select optimal filter media, a comprehensive study of the electrostatic parameters of all components in the water treatment process was carried out. Experimental studies of physical quantities that are key to this process were performed. The relationship between the turbidity parameters of the studied waters and the ζ-potential of the colloids contained in them was shown. Seasonal changes in the hydrochemical composition of the treated waters were studied. The connection between electrochemical parameters of clay particles and the processes of their sedimentation in aqueous suspension is given. The dependences of turbidity on time and the ratio of average turbidity values to the minimum and maximum ones at the water intake of the Dniester-Chernivtsi water supply system during 2005-2015 were reviewed and presented. The dynamics of changes in the parameters of turbidity and ζ-potential in the structures of the technological chain of water treatment during the periods of summer-autumn floods and low-water winter period was studied. The effect of the coagulant used at the studied water treatment facility on the electrostatic parameters of the purified colloidal particles, in particular, on changing the structure of the electric double layer of clay particles, which lead to the coagulation and reduction in the treated water turbidity, was analyzed. The optimal conditions of using polystyrene foam and zeolite filter media were determined. Ion exchange properties enabled the zeolite to efficiently remove fine colloidal particles with positively charged cores out of the purified aqueous suspension, which were not completely covered with a layer of potential-forming ions. However, they produced impact only in the short-term initial stage of filtering. Therefore, they cannot be recommended for using for long-term water treatment processes at water treatment facilities. This phenomenon is due to the limited ion exchange adsorption properties of zeolite. The effective filtration of colloidal particles through zeolite in the year-round mode of operation at the studied water treatment facility is mainly associated with the developed outer surface of its grains, which provides mechanical interception and retention of colloidal particles.
 Conclusions. The connection between the turbidity parameters and colloids ζ-potential of the purified aqueous suspension for the conditions of water quality formation in the upper reaches of the Dniester River has been established. The determined values of the ζ-potential of colloids enabled to find out that the polystyrene foam filter media is more expedient to use during the flood periods, and the application of the zeolite media has a higher efficiency during the low-water periods. The ion exchange properties of zeolite can ensure a high level of water purification during floods; however it can be only efficient at the initial stage of filtration. Effective mechanical interception and retention of colloidal particles in the year-round regime is provided by the developed surface of its grains. The combined polystyrene foam and zeolite filter media is recommended to use to solve the problems of water treatment throughout the year.

Electrostatic Balance Parameter Mediated Energy Functions‐Toward the Stability and Performance of Explosives

AbstractIt is a main challenge to achieve a fine balance between high energy density and good molecular stability in energetic material research. The electrostatic balance parameter (ν), a universal parameter, that describes the coordination relationship between energy and stability of explosives may achieve this purpose. The strain energy, resonance energy, and large π‐π separation energy were calculated from the perspective of molecular transformability to evaluate the stability of explosive molecules, and ν was used to mediate the three parameters.

Singlet-triplet interaction of the adiabatic terms [formula omitted] and [formula omitted] in the linear triatomic molecules

The paper introduces the 4x4 vibronic matrix that describes singlet–triplet interaction of adiabatic terms 1Σ+ and 3Σ+ via deformation π-modes of the linear triatomic system. Our analysis takes into account spin-orbital coupling in ab initio Breit-Pauli form in the framework of two-electronic model. It is shown that the symmetry operators of electronic Hamiltonian include both space operations (acting on electronic coordinates) and matrix operations (acting on electronic spins). Eigenvalues of vibronic matrix (i.e. potential energy surfaces) are invariants of the molecular symmetry group C∞ν. The 4x4 vibronic matrix includes 4 electrostatic parameters and 3 parameters caused by spin-orbital interaction.

Implicit Solvents for the Polarizable Atomic Multipole AMOEBA Force Field.

Computational protein design, ab initio protein/RNA folding, and protein-ligand screening can be too computationally demanding for explicit treatment of solvent. For these applications, implicit solvent offers a compelling alternative, which we describe here for the polarizable atomic multipole AMOEBA force field based on three treatments of continuum electrostatics: numerical solutions to the nonlinear and linearized versions of the Poisson-Boltzmann equation (PBE), the domain-decomposition conductor-like screening model (ddCOSMO) approximation to the PBE, and the analytic generalized Kirkwood (GK) approximation. The continuum electrostatics models are combined with a nonpolar estimator based on novel cavitation and dispersion terms. Electrostatic model parameters are numerically optimized using a least-squares style target function based on a library of 103 small-molecule solvation free energy differences. Mean signed errors for the adaptive Poisson-Boltzmann solver (APBS), ddCOSMO, and GK models are 0.05, 0.00, and 0.00 kcal/mol, respectively, while the mean unsigned errors are 0.70, 0.63, and 0.58 kcal/mol, respectively. Validation of the electrostatic response of the resulting implicit solvents, which are available in the Tinker (or Tinker-HP), OpenMM, and Force Field X software packages, is based on comparisons to explicit solvent simulations for a series of proteins and nucleic acids. Overall, the emergence of performative implicit solvent models for polarizable force fields opens the door to their use for folding and design applications.

Impact of Grinding of Printed Circuit Boards on the Efficiency of Metal Recovery by Means of Electrostatic Separation

This paper analyses the impact of the method of grinding printed circuit boards (PCBs) in a knife mill on the efficiency and purity of products obtained during electrostatic separation. The separated metals and plastics and ceramics can be used as secondary raw materials. This is in line with the principle of circular economy. Three different screen perforations were used in the mill to obtain different sizes of ground grains. Moreover, the effect of cooling the feed to cryogenic temperature on the final products of separation was investigated. The level of contamination of the concentrate, intermediate, and waste obtained as a result of the application of fixed, determined electrostatic separation parameters was assessed using ICP-AES, SEM–EDS, XRD, and microscopic analysis as well as specific density. The yields of grain classes obtained from grinding in a knife mill were tested through sieve analysis and by using a particle size analyser. The test results indicate that using a knife mill with a 1 mm screen perforation along with cooling the feed to cryogenic temperature significantly improves the efficiency of the process. The grinding products were characterised by the highest release level of the useful substance—metals in the free state. The purity of the concentrate and waste obtained from electrostatic separation was satisfactory, and the content of the intermediate, in which conglomerates of solid metal–plastic connections were present, was very low. The yield of concentrate and waste amounted to 26.2% and 71.0%, respectively. Their purity, reflected in the content of the identified metals (valuable metals), was at the level of 93.3% and 0.5%, respectively. In order to achieve effective recovery of metals from PCBs by means of electrostatic separation, one should strive to obtain a feed composed of grains <1000 μm and, optimally, <800 μm.

Multipolar electrostatics for hairpin and pseudoknots in RNA: Improving the accuracy of force field potential energy function.

Molecular dynamics (MD) simulations that rely on force field methods has been widely used to explore the structure and function of RNAs. However, the current commonly used force fields are limited by the electrostatic description offered by atomic charge, dipole and at most quadrupole moments, failing to capture the anisotropic picture of electronic features. Actually, the distribution of electrons around atomic nuclei is not spherically symmetric but is geometry dependent. A multipolar electrostatic model based on high rank multipole moments is described in this work, which allows us to combine polarizability and anisotropy of electron density. RNA secondary structure was taken as a research system, and its substructures including stem, loops (hairpin loop, bulge loop, internal loop, and multi-branch loop), and pseudoknots (H-type and K-type) were investigated, respectively, as well as the hairpin. First, the atom-atom electrostatic properties derived from one chain of a duplex RNA 2MVY in our previous work (Ref. 58) were measured by the pilot RNA systems of hairpin, hairpin loop, stem, and H-type pseudoknot, respectively. The prediction results were not satisfactory. Consequently, to obtain a general set of electrostatic parameters for RNA force fields, the convergence behavior of the atom-atom electrostatic interactions in the pilot RNA systems was explored using high rank atomic multipole moments. The pilot RNA systems were cut into four types of different-sized molecular fragments, and the single nucleotide fragment and nucleotide-paired fragment proved to be the most reasonable systems for base-unpairing regions and base-pairing regions to investigate the convergence behavior of all types of atom-atom electrostatic interactions, respectively. Transferability of the electrostatic properties drawn from the pilot RNA systems to the corresponding test systems was also investigated. Furthermore, the convergence behavior of atomic electrostatic interactions in other substructures including bulge loop, internal loop, multi-branch loop, and K-type pseudoknot was expected to be modeled via the hairpin.

Electroosmotic Flow Grows with Electrostatic Coupling in Confining Charged Dielectric Surfaces

In this work, the effects of polarization of confining charged planar dielectric surfaces on induced electroosmotic flow are investigated. To this end, we use dissipative particle dynamics to model solvent and ionic particles together with a modified Ewald sum method to model electrostatic interactions and surfaces polarization. A relevant difference between counterions number density profiles, velocity profiles, and volumetric flow rates obtained with and without surface polarization for moderate and high electrostatic coupling parameters is observed. For low coupling parameters, the effect is negligible. An increase of almost 500% in volumetric flow rate for moderate/high electrostatic coupling and surface separation is found when polarizable surfaces are considered. The most important result is that the increase in electrostatic coupling substantially increases the electroosmotic flow in all studied range of separations when the dielectric constant of electrolytes is much higher than the dielectric constant of confining walls. For the higher separation simulated, an increase of around 340% in volumetric flow rate when the electrostatic coupling is increased by a factor of two orders of magnitude is obtained.

Electrostatically Sprayed Nanostructured Electrodes for Energy Conversion and Storage Devices

AbstractThe electrostatic spray method is a promising nonvacuum technique for efficient deposition of thin films from solutions or dispersions. The multitude of electrostatic spray process parameters, including surface tension, viscosity, and conductivity of the liquid, applied voltage, nozzle size, and flow rate, make electrostatic spray deposition very versatile for the morphological engineering of nanostructured films. The current state‐of‐the‐art in electrostatic spraying can produce exceptional morphologies. Such tailoring of morphologies is notably useful in electrochemical applications where high electrolyte‐accessible surface area often improves performance. Interesting morphologies of metal oxides and their composites are highlighted, including nanopillars, nanoferns, and porous microspheres produced by electrostatic spraying to enhance energy conversion and storage performance. The physics associated with the electrostatic spray process and morphology control using it are also presented. The manuscript highlights the potential of electrospray processing for producing thin films of controlled microstructure, from ultrasmooth layers in organic photovoltaics and perovskite photovoltaics to hierarchical nanostructured films for anodes and photoanodes. It aims to help researchers appreciate essential aspects of electrostatic spray deposition efficiency, process control, and morphology engineering for energy conversion (e.g., solar cell, fuel cell, and photoelectrochemical cell) and energy storage (e.g., lithium‐ion battery and supercapacitor) electrodes.

The 2D Debye length: An analytical study of weak charge screening in 2D semiconductors

Simple perturbations (such as a line charge or a sheet charge) in 2D semiconducting materials create difficult solutions to the Poisson equation due to the non-uniform out-of-plane electric fields that result from the perturbative charge. Here, for the first time, we determine simple and general analytical expressions for the potential profile, its Fourier representation, the corresponding 2D Debye screening length, and the charge screening behavior in 2D semiconductors due to a line charge perturbation. In contrast to conventional 3D semiconductors, we find that the 2D Debye length goes as 1/ND,2D, where ND,2D is the 2D semiconductor doping density, and this leads to markedly different Debye lengths as compared to those determined by the conventional (3D) Debye length expression. We show that the potential profile due to a charge perturbation in a 2D semiconductor does not decay exponentially with distance from the perturbation (as is the case for 3D semiconductors) but instead decays logarithmically in the immediate vicinity of the perturbation and as 1/x2 when the distance is approximately equal to or greater than the 2D Debye length. Overall, this work establishes an analytical approach for determining a fundamental electrostatic parameter for 2D semiconductors.

Systematic optimization of a fragment-based force field against experimental pure-liquid properties considering large compound families: application to oxygen and nitrogen compounds.

The CombiFF approach is a workflow for the automated refinement of force-field parameters against experimental condensed-phase data, considering entire classes of organic molecules constructed using a fragment library via combinatorial isomer enumeration. One peculiarity of this approach is that it relies on an electronegativity-equalization scheme to account for induction effects within molecules, with values of the atomic hardness and electronegativity as electrostatic parameters, rather than the partial charges themselves. In a previous article [M. P. Oliveira, M. Andrey, S. R. Rieder, L. Kern, D. F. Hahn, S. Riniker, B. A. C. Horta and P. H. Hünenberger, J. Chem. Theory. Comput. 2020, 16, 7525], CombiFF was introduced and applied to calibrate a GROMOS-compatible united-atom force field for the saturated acyclic (halo-)alkane family. Here, this scheme is employed for the construction of a corresponding force field for saturated acyclic compounds encompassing eight common chemical functional groups involving oxygen and/or nitrogen atoms, namely: ether, aldehyde, ketone, ester, alcohol, carboxylic acid, amine, and amide. Monofunctional as well as homo-polyfunctional compounds are considered. A total of 1712 experimental liquid densities ρliq and vaporization enthalpies ΔHvap concerning 1175 molecules are used for the calibration (339 molecules) and validation (836 molecules) of the 102 non-bonded interaction parameters of the force field. Using initial parameter values based on the GROMOS 2016H66 parameter set, convergence is reached after five iterations. Given access to one processor per simulated system, this operation only requires a few days of wall-clock computing time. After optimization, the root-mean-square deviations from experiment are 29.9 (22.4) kg m−3 for ρliq and 4.1 (5.5) kJ mol−1 for ΔHvap for the calibration (validation) set. Thus, a very good level of agreement with experiment is achieved in terms of these two properties, although the errors are inhomogeneously distributed across the different chemical functional groups.

Computational and data driven molecular material design assisted by low scaling quantum mechanics calculations and machine learning.

Electronic structure methods based on quantum mechanics (QM) are widely employed in the computational predictions of the molecular properties and optoelectronic properties of molecular materials. The computational costs of these QM methods, ranging from density functional theory (DFT) or time-dependent DFT (TDDFT) to wave-function theory (WFT), usually increase sharply with the system size, causing the curse of dimensionality and hindering the QM calculations for large sized systems such as long polymer oligomers and complex molecular aggregates. In such cases, in recent years low scaling QM methods and machine learning (ML) techniques have been adopted to reduce the computational costs and thus assist computational and data driven molecular material design. In this review, we illustrated low scaling ground-state and excited-state QM approaches and their applications to long oligomers, self-assembled supramolecular complexes, stimuli-responsive materials, mechanically interlocked molecules, and excited state processes in molecular aggregates. Variable electrostatic parameters were also introduced in the modified force fields with the polarization model. On the basis of QM computational or experimental datasets, several ML algorithms, including explainable models, deep learning, and on-line learning methods, have been employed to predict the molecular energies, forces, electronic structure properties, and optical or electrical properties of materials. It can be conceived that low scaling algorithms with periodic boundary conditions are expected to be further applicable to functional materials, perhaps in combination with machine learning to fast predict the lattice energy, crystal structures, and spectroscopic properties of periodic functional materials.

Anisotropic electrostatic models of nitrogen and phosphorus: the variation and the interpretability of the electrostatic parameters in response to structure variation

The anisotropic electrostatic parameters of truncated multipole expansion (atomic dipole and quadrupole) obtained for a series of nitrogen and phosphorus containing compounds allow for a reasonable physical interpretation and appear to be predictable in response to chemical substituent variation. These findings will be useful for prediction of anisotropic parameters in next generation force fields without the need to resort to quantum chemical calculations.

Hybrid approach to modeling large area field emitters

Large area field electron emitters, typically consisting of several thousands of nanotips, pose a major challenge since numerical modeling requires enormous computational resources. We propose a hybrid approach where the local electrostatic field enhancement parameters of an individual emitter are determined numerically while electrostatic shielding and anode-proximity effects are incorporated using recent analytical advances. The hybrid model is tested numerically on an ordered arrangement of emitters and then applied to recent experimental results on randomly distributed gold nanocones. Using the current-voltage data of two samples with vastly different emitter densities but having similar nanocone sizes, we show that an appropriate modeling of the emitter apex together with the analytical results on shielding and anode-proximity effects leads to consistent results for the apex radius of curvature. In both cases, the I−V data are approximately reproduced for Ra≃9 nm. Importantly, it is found that anode-proximity plays a significant role in counter-balancing electrostatic shielding, and ignoring this effect results in the requirement of a much smaller value of Ra.

QSPR studies on the blood-air partition coefficient of volatile organic compounds using theoretical descriptors derived from electrostatic potentials on molecular surface

Volatile organic compounds (VOCs) is a sort of important environmental pollutant. Based on study on Quantitative Structure-Property Relationship (QSPR), geometrical optimization and electrostatic potential calculations have been performed for 143 VOC molecules at the HF/6-31G* level of theory. A number of statistically-based parameters have been obtained. Multiple Linear Regression (MLR) and back-propagation artificial neural network (BP-ANN) nonlinear regression are used for the model building. The result shows that the BP-ANN can better expresses the relation between molecule surface electrostatic potential and blood-air partition coefficient than MLR, and the QSPR model established has comparatively stronger stability and predictive ability using BP-ANN method. The result also proves the applicability of molecule surface electrostatic potential parameter in QSPR study of Volatile organic chemical.

Ab-initio investigation of hydrogen sorption in Ti functionalized modified calix[4]pyrrole-benzene

Hydrogen is an ecofriendly and affordable alternative for fossil fuels. Storage of hydrogen with high hydrogen weight percentage is the prime obstacle to use it as a fuel. The hydrogen storage capacity in Ti functionalized modified calix[4]pyrrole-benzene is explored using density functional theory. Hydrogens are sequentially adsorbed over functionalized Ti atoms as well as over the π−complexes of acetylenic linkages and pyrrole rings. The host stores 28 H2 with a maximum H wt% of 10.1 and sorption energies in the range of 0.50–0.25 eV. Mechanism of the quasi-molecular adsorption is explained through the analyses of electrostatic potential, distance parameters, and charges. Findings of molecular dynamics, van ‘t Hoff desorption analysis, and the occupation number prove that the host is thermally stable and stores H2 reversibly. Ti functionalized modified calix[4]pyrrole-benzene proves to be a potential hydrogen storage candidate fulfilling the 2020 targets set by the US, DOE.

Analysis of Temperature Effect in Quadruple Gate Nano-scale FinFET

Quadruple gate FinFET is a promising candidate among other multi-gate MOS devices due to it’s better scalability and higher short channel effect suppression capability in advanced technology node. In this work, we report the effect of temperature on various performance metrics of quadruple gate FinFET like electrostatic integrity, carrier mobility, switching ratio, analog/RF, and linearity parameters with the help of well-calibrated numerical device simulation-based study (TCAD). While increasing the temperature from 250 °K to 450 °K, due to the enhanced bulk phonon scattering, degradation in carrier effective mobility is observed. Sub-threshold swing and drain induced barrier lowering coefficient vary linearly with temperature. At high temperature, due to the reduced carrier mobility, degradation in the analog figure of merits is observed. RF performance parameters also degrade primarily due to the enhanced gate capacitance and reduced trans-conductance. However, some linearity parameter improves at high temperature due to the reduced magnitude of the higher-order derivative of trans-conductance. Another major contribution of this work is, we demonstrate the inflection point or temperature compensation point in some analog/RF performance metrics where the device characteristics almost invariant with temperature.

An Analytical Modeling of Conical Gate-All-Around Tunnel Field Effect Transistor

In this paper a new analytical modeling of Conical Gate-All-Around Tunnel Field Effect Transistor has been proposed and verified by TCAD Simulation. The Electrostatic parameters of the conical structure are modeled from two dimensional Poisson’s Equation using Parabolic Approximation Method. The electrostatic performance of surface potential and drain current of conical structure is compared with the cylindrical structure. The present model with optimized tapering ratio of 0.9 parades enhanced electrostatic behavior compared to cylindrical structure. The results divulge the conical device model provides better ON drain current, high transconductance and reduced threshold voltage at drain side. Thus, the conical structure can be a possible replacement of cylindrical structure with optimized tapering ratio for low-power applications.

Identification and Investigation of Chalcone Derivatives as Calcium Channel Blockers: Pharmacophore Modeling, Docking Studies, In vitro Screening, and 3D-QSAR Analysis.

The chalcones were reported to have many biological activities by showing affinity towards many enzymatic targets. The effect of nitric oxide (NO) on calcium channel was extensively studied in different animals; the study was also carried out for NO donor drug and its effect on calcium channel. Till date, the inhibition of calcium channel is of prime importance in the medicinal chemistry to discover newer vascular smooth muscle relaxant drugs. The main objective of this work is to carry out in silico and in vitro evaluation of NO donor chalcones for calcium channel blocking potency. The present work includes in silico evaluation of chalcone derivatives for calcium channel blocking potency. The promising scaffolds were identified after pharmacophore modeling and docking study. The in vitro screening of 21 lead molecules for calcium channel blocking potency was carried out on pulmonary veins of adult goat, IC50 values were determined and 3D QSAR was performed. The pharmacophore modeling revealed that hydrogen bond donor, hydrogen bond acceptor, and hydrophobic groups are important features for calcium channel blocking activity. The docking study revealed the existence of hydrophobic, hydrogen bond and Vander wall's interactions between amino acid residues and ligands. The in vitro screening showed that the compounds AI6, Ca2, and D8 were potent, produced 4.756, 3.608 and 5.211 μM of IC50 respectively, whereas the standard Nifedipine showed the potency of 1.304 μM of IC50. The 3D QSAR study explained the importance of different steric and electrostatic parameters and their correlation for L type calcium channel blocking activity. This study showed that the chalcone scaffold with NO donor capacity is promising for designing novel calcium channel blockers to treat vascular disorders.

Balanced polarizable Drude force field parameters for molecular anions: phosphates, sulfates, sulfamates, and oxides.

Polarizable force fields are emerging as a more accurate alternative to additive force fields in terms of modeling and simulations of a variety of chemicals including biomolecules. Explicit treatment of induced polarization in charged species such as phosphates and sulfates offers the potential for achieving an improved atomistic understanding of the physical forces driving their interactions with their environments. To help achieve this, in this study we present balanced Drude polarizable force field parameters for molecular ions including phosphates, sulfates, sulfamates, and oxides. Better balance was primarily achieved in the relative values of minimum interaction energies and distances of the anionic model compounds with water at the Drude and quantum mechanical (QM) model chemistries. Parametrization involved reoptimizing available parameters as well as extending the force field to new molecules with the goal of achieving self-consistency with respect to the Lennard-Jones and electrostatic parameters targeting QM and experimental hydration free energies. The resulting force field parameters achieve consistent treatment across the studied anions, facilitating more balanced simulations of biomolecules and small organic molecules in the context of the classical Drude polarizable force field. Graphical abstract.