Charge Density Parameters Research Articles

Study on the competitive reduction mechanism of C and CO on Fe2O3 in blast furnace ironmaking

The competitive reduction behaviour of C and CO on the surface of Fe2O3 in blast furnaces was studied based on experiments and the first-principles calculations. The material morphology and element distribution of Fe2O3 under the conditions of C, CO and C + CO reduction were compared. In order to further investigate the competitive reduction behaviour of C and CO on the Fe2O3 surface, based on the first-principles calculation, the adsorption mechanism of C and CO on the α-Fe2O3(001) surface was studied by calculating the parameters of bond length, adsorption energy, charge density and state density. The results showed that under the condition of C + CO co-reduction, the reduction degree of Fe2O3 is better. When CO was adsorbed on the α-Fe2O3 (001) surface alone, the adsorption energy of the adsorption structure was −0.549 eV. The state density peak of the CO molecule on the left side of the Fermi level was sharper, and the electron delocalization around the CO molecule was weaker. Compared with the C atom, the CO molecule was less easily adsorbed on the α-Fe2O3 (001) surface, and the structure stability of the adsorbed products generated by the CO molecule was also lower. Compared with the adsorption of C and CO on the α-Fe2O3 (001) surface alone, the co-adsorption energy of C atom and CO molecule was relatively low, which was −7.755 eV, and the co-adsorption structure was more stable, and the presence of CO was more conducive to the interactions between C and α-Fe2O3 (001) surface.

Molecular Insights into Water-Chloride and Water-Water Interactions in the Supramolecular Architecture of Aconine Hydrochloride Dihydrate.

Despite the previous preparation of aconine hydrochloride monohydrate (AHM), accurate determination of the crystal's composition was hindered by severely disordered water molecules within the crystal. In this study, we successfully prepared a new dihydrate form of the aconine hydrochloride [C25H42NO9+Cl-·2(H2O), aconine hydrochloride dihydrate (AHD)] and accurately refined all water molecules within the AHD crystal. Our objective is to elucidate both water-chloride and water-water interactions in the AHD crystal. The crystal structure of AHD was determined at 136 K using X-ray diffraction and a multipolar atom model was constructed by transferring charge-density parameters to explore the topological features of key short contacts. By comparing the crystal structures of dihydrate and monohydrate forms, we have observed that both AHD and AHM exhibit identical aconine cations, except for variations in the number of water molecules present. In the AHD crystal, chloride anions and water molecules serve as pivotal connecting hubs to establish three-dimensional hydrogen bonding networks and one-dimensional hydrogen bonding chain; both water-chloride and water-water interactions assemble supramolecular architectures. The crystal packing of AHD exhibits a complete reversal in the stacking order compared to AHM, thereby emphasizing distinct disparities between them. Hirshfeld surface analysis reveals that H···Cl- and H···O contacts play a significant role in constructing the hydrogen bonding network and chain within these supramolecular architectures. Furthermore, topological analysis and electrostatic interaction energy confirm that both water-chloride and water-water interactions stabilize supramolecular architectures through electrostatic attraction facilitated by H···Cl- and H···O contacts. Importantly, these findings are strongly supported by the existing literature evidence. Consequently, navigating these water-chloride and water-water interactions is imperative for ensuring storage and safe processing of this pharmaceutical compound.

On the importance of unconventional Cu⋯π interaction in tetrachloro-bis(1,10-phenanthroline)-dicopper(II) complex: Insights from experiment and theory

A copper-phenanthroline complex, namely [bis(μ2‑chloro)-dichloro-bis(1,10-phenanthroline)-di-copper(II)] has been synthesized and structurally characterized by single-crystal X-ray diffraction. The X-ray structure of the complex is stabilized through the hydrogen bond, π⋯π, and Cu⋯π interactions. The Cu⋯π interactions of the title complex along with two other complexes (retrieved from CSD) are analyzed in great detail through various theoretical calculations. Hirshfeld surface analysis and fingerprint plot quantify the non-covalent interactions. The interaction energies associated with intermolecular interactions have been calculated based on QTAIM (Quantum Theory of atoms in molecule). The analysis of topological parameters of charge density at (3, −1) bond critical points characterize the interactions as “closed-shell” interactions. The non-covalent interactions are further characterized by the Non-Covalent Interaction (NCI) plot index, Independent Gradient Module based on Hirshfeld partition of molecular density (IGMH), and Intrinsic Bond Strength Index for Weak interaction (IBSIW).

Synthesis, characterization, crystal structure, Hirshfeld analysis and theoretical investigation of 5-(4-methoxyphenyl)-7-phenyl-2-(pyridin-2-yl)imidazo[1,2-a]pyridine-8-carbonitrile

Synthesis of 5-(4-methoxyphenyl)-7-phenyl-2-(pyridin-2-yl)imidazo[1,2-a]pyridine-8-carbonitrile has been carried out by the reaction between 1-(pyridin-2-yl)ethanone and 2-amino-6-(4-methoxyphenyl)-4-phenylnicotinonitrile under microwave irradiation. The synthesized compound has been characterized on the basis of spectroscopic data such as 1H NMR, 13C NMR, FTIR, HRMS, and single crystal XRD. The XRD data reveals that the solid-state structure of the compound belongs to the triclinic system of the space group P1‾ and is stabilized through C–H⋯N, C–H⋯π, and π⋯π interactions. Quantification of the non-covalent interactions is analyzed through Hirshfeld surface analysis. The non-covalent interactions are characterized through Bader's Theory of “Atoms-in-Molecules” (AIM) and the “Non-covalent Interaction” (NCI) plot index. The analysis of topological parameters of charge density at the (3, −1) bond critical points (BCPs) classified the interactions as “closed-shell” interactions.

Landau-Ginzburg theory of charge density wave formation accompanying lattice and electronic long-range ordering

We propose an analytical Landau-Ginzburg theory of the charge density waves coupled with lattice and electronic long-range order parameters. Examples of long-range order include electronic wave function of superconducting Cooper pairs, structural distortions, electric polarization, and magnetization. We formulate the Landau-Ginzburg free energy density as power expansion with respect to the charge density and other long-range order parameters, as well as their spatial gradients, and biquadratic coupling terms. We introduced a biquadratic coupling between the charge density gradient and long-range order parameters, as well as nonlinear higher gradients of the long-range order parameters. The biquadratic gradient coupling is critical to the appearance of different spatially-modulated phases in charge-ordered ferroics and high-temperature superconductors. We derived the thermodynamic conditions for the stability of the spatially-modulated phases, which are the intertwined spatial waves of charge density and lattice/electronic long-range order. The analytical expressions for the energies of different phases, corresponding order parameters, charge density waves amplitudes and modulation periods, obtained in this work, can be employed to guide the comprehensive physical explanation, deconvolution and Bayesian analysis of experimental data on quantum materials ranging from charge-ordered ferroics to high-temperature superconductors.

Study of MFL signal identification in pipelines based on non-uniform magnetic charge distribution patterns

Magnetic flux leakage (MFL), a pipeline internal detection, is the mainstream technology for international oil and gas pipeline safety maintenance. To address the problem of large errors in the assessment of defects in pipeline inspection by existing theoretical analysis models, this paper introduces the charge density parameter to establish a mathematical model of non-uniform magnetic charge for pipeline leakage detection and calculates the non-uniform distribution pattern of magnetic charge on the defect side wall. The contour plot method is proposed to visually analyze the size of defects. To compare the error between uniform and non-uniform models, and verify the correctness of the theoretical model, experiments were systematically conducted on the X70 pipeline with internal MFL technology. The results show that: the magnetic charge distribution curve is symmetrically shaped at the center of the defect, with a valley at the center and two peaks at the defect edge. As the defect depth and width increase, the magnetic charge density increases sharply near the surface and edge. The peak-to-valley spacing and peak-to-valley values in the contour map of the MFL signal can directly reflect the location and size of defects. The signal characteristic values follow the trend of a first-order decreasing exponential function as the value of the lift-off increases. The first-order derivative of the signal characteristic value tends to decrease and then increase as the mesh size decreases, and the extreme point of the derivative curve is the best mesh size.

Interactive-excited waterdrop triboelectric nanogenerator with ultrahigh charge density and instantaneous power

In recent years, waterdrop triboelectric nanogenerator (WD-TENG) has attracted much attention in the field of energy harvesting. However, the charge density of waterdrop after friction with other materials is low, limiting the output performance and real application of WD-TENGs. For solving this problem, an interactive-excited strategy is introduced here by combining a WD-TENG and a Kelvin waterdrop generator. As excited by WD-TENG, Kelvin waterdrop generator becomes much easier to start electrification with controllable polarity. As excited by Kelvin waterdrop generator in return, the hugely improved output performances of WD-TENG are achieved. The charge quantity of a single waterdrop reaches 144 nC, and the corresponding charge density is as high as 2304 nC/mL. The output voltage and instantaneous power reach as high as 1760 V and 54.6 mW, respectively. The obtained parameters of charge density and instantaneous power are much more than previous records of WD-TENGs. Also, it has been demonstrated that a single waterdrop of 62.50 μL can light up 320 LEDs. The interactive-excited strategy hugely improves the charge density and instantaneous power of WD-TENG, which has promising applications in harvesting waterdrop energy and developing self-powered systems.

Hydrogen bonding probes electron density variations at the basic center in substituted alkyl benzoates: Theory and experiment

AbstractTheoretical computations of charge density parameters are juxtaposed to experimental spectroscopic shifts induced by hydrogen bonding for a series of 21 substituted in the aromatic ring ethyl and methyl benzoates. Strong correlations between atomic charges at the proton accepting atom and the shifts of methanol O–H frequencies are established. Hirshfeld, Charge Model 5 (CM5), and natural population analysis (NPA) atomic charges are evaluated using ωB97X‐D/6‐311++G(3df,2pd) and MP2/6‐311++G(3df,2pd) computations. The results obtained reveal the power of hydrogen bond measurements in characterizing the variations of electron densities at the proton accepting center within a series of structurally related molecules. The limits of application of the approach are outlined.

Silica Nanoparticle Reinforced Composites as Transparent Elastomeric Damping Materials

Inspired by the structure of the cornea, which is the transparent front part of the eye, we developed a transparent and tough silica composite elastomer consisting of poly[di(ethylene glycol)methyl ether methacrylate] (PMEO2MA) and 110 nm spherical silica particles without using an organic cross-linking agent. While filler composite elastomers, such as reinforced rubbers, have complex compositions containing multiple additives (dispersants, plasticizers, vulcanizing agents, etc.), the composition of our composite elastomer is very simple. With an increased amount of silica particles, the fracture energy of the composite elastomer (20.2 MJ m–3) was improved by 25 times compared to that of unfilled PMEO2MA (0.8 MJ m–3). Nanoscale mapping using atomic force microscopy elucidated the presence of an interface layer (IL) of approximately 15 nm thickness with a high elastic modulus near the silica particles in the composite elastomer. The fracture energy of the composite elastomer was found to be a maximum when the particle surface distance was approximately 30 nm. This particle surface distance meant that the ILs were just in contact with each other. The surface charge density and Hansen solubility parameter of the silica particles indicated the ionization of silanol groups and interactions caused by hydrogen bonding between polymer chains and the silica surface. The array of silica particles embedded with intervals of a few nanometers was expected to be able to effectively dissipate deformation energy as heat due to shear strain and friction between the particle surface and polymer matrices. Measurements of the vibration-damping properties revealed that the loss factor of the composite elastomer was significantly higher than that of the unfilled elastomer, indicating that the composite elastomer in this study could be applied as an interlayer film for laminated glass in automotive and architectural applications.

Critical View on Buffer Layer Formation and Monolayer Graphene Properties in High-Temperature Sublimation

In this work we have critically reviewed the processes in high-temperature sublimation growth of graphene in Ar atmosphere using closed graphite crucible. Special focus is put on buffer layer formation and free charge carrier properties of monolayer graphene and quasi-freestanding monolayer graphene on 4H–SiC. We show that by introducing Ar at higher temperatures, TAr, one can shift the formation of the buffer layer to higher temperatures for both n-type and semi-insulating substrates. A scenario explaining the observed suppressed formation of buffer layer at higher TAr is proposed and discussed. Increased TAr is also shown to reduce the sp3 hybridization content and defect densities in the buffer layer on n-type conductive substrates. Growth on semi-insulating substrates results in ordered buffer layer with significantly improved structural properties, for which TAr plays only a minor role. The free charge density and mobility parameters of monolayer graphene and quasi-freestanding monolayer graphene with different TAr and different environmental treatment conditions are determined by contactless terahertz optical Hall effect. An efficient annealing of donors on and near the SiC surface is suggested to take place for intrinsic monolayer graphene grown at 2000 ∘C, and which is found to be independent of TAr. Higher TAr leads to higher free charge carrier mobility parameters in both intrinsically n-type and ambient p-type doped monolayer graphene. TAr is also found to have a profound effect on the free hole parameters of quasi-freestanding monolayer graphene. These findings are discussed in view of interface and buffer layer properties in order to construct a comprehensive picture of high-temperature sublimation growth and provide guidance for growth parameters optimization depending on the targeted graphene application.

Hybrid Modeling and Sensitivity Analysis on Reduced Graphene Oxide Field-Effect Transistor

The reduced graphene oxide (RGO) field-effect transistor (FET) has been developed and applied in various areas. However, the effective modeling and sensitivity analysis on RGO FET is still a very challenging problem due to the randomness of bandgap and density of states (DOS) in RGO. In this paper, we propose to solve the RGO FET modeling problem by integrating the data-driven thinking and the graphene FET model to develop a hybrid model. The proposed model takes advantages of the similarities between graphene and RGO to generalize the existing graphene FET model, and employs RGO FET drain-current data to characterize the specificity of the model. The basic idea in the proposed model is to modify the graphene DOS to approximate the RGO DOS so that the charge density, mobility and other parameters can be achieved through the approximated RGO DOS. We validate the model accuracy with the RGO FET based sensors that detect chemical concentrations in the aqueous environment. The RGO FET sensitivity analysis is also demonstrated to provide guidance for RGO FET application and manufacturing.

First-principles investigations of the structural, optoelectronic, magnetic and thermodynamic properties of hydride perovskites XCuH3 (X = Co, Ni, Zn) for hydrogen storage applications

Hydrogen storage in current years has become significant and momentous for researcher’s interest because hydrogen as an energy source can be utilized. In the current study, the structural, optoelectronic, magnetic, and thermodynamic properties along with bader charge density parameters of novel combinations of hydride perovskites such as CoCuH3, NiCuH3 and ZnCuH3 are investigated by first principles method in the frame work of density functional theory (DFT). The comprehensive investigations have been made while using three cations (Co, Ni and Zn) in ABH3 cubical order of symmetry phases. The band structures are plotted along with partial density of states, which manifestly predict that XCuH3 (X = Co, Ni and Zn) hydrides possess metallic behavior due to overlapping of conduction and valence bands. The lattice parameters of XCuH3 (X = Co, Ni, Zn) are calculated on the basis of Generalized Gradient Approximations (GGA), which are indexed as 3.3287 Å, 3.3245 Å and 3.6129 Å for XCuH3 (X = Co, Ni, Zn), respectively. However, to dominate the limitations of GGA functional, LDA + U (an effective Hubbard parameter) has been utilized and calculated improved lattice parameters are 3.4815 Å, 3.2838 Å and 3.4867 Å for XCuH3 (X = Co, Ni, Zn), respectively. The dielectric function, refractive index, extinction coefficient, optical conductivity are calculated on the basis of Kramer-Kroing principle and their results show that NiCuH3 is more appropriate material for hydrogen storage applications. The gravimetric ratio of hydrogen storage capacities are determined as 2.8 wt.%, 3.0 wt.%, and 2.7 wt.% for CoCuH3, NiCuH3 and ZnCuH3, respectively. Antiferomagnetism is reported for NiCuH3 and ZnCuH3, while magnetism has been observed for CoCuH3 in line with the results calculated through DOS and PDOS for studied materials. The current study is the first computational attempt of XCuH3, which may contribute outstanding amelioration for future investigations in hydrogen storage applications.

π‐Hydrogen Bonding Probes Chemical Reactivity: Bromination of a CC Double Bond and Electrophilic Aromatic Benzylation

AbstractThe reactivity trends for two basic organic reactions – addition of bromine to a CC double bond in alkenes and electrophilic aromatic benzylation of alkyl‐ and halobenzenes – are rationalized using both experimental and theoretical quantities. Literature kinetic data are employed. The shifts of phenol O–H stretching frequency upon π‐hydrogen bonding (Δν(OH)exp) with the nucleophilic reactants are shown to provide a quantitative measure of the reactivity for the considered reactions. Very good correlations between Δν(OH)exp and theoretically estimated charge density parameters (atomic charges and shifts of molecular electrostatic potential) show that the O–H frequency shifts reflect the variations of nucleophilic properties in the reaction centers upon structural changes. The Δν(OH)exp shifts perform much better in quantifying reactivity trends than usually employed experimental quantities, such as gas‐phase basicities and proton affinities.

Synthesis of Novel α-amidino Carboxylic Acids and their Use as H-Bond Catalysts in Strecker Reaction.

A wide variety of synthesized amidine derivatives are bioactive compounds. They show a vast range of medical properties. Therefore, a simple route for synthesis of novel class of amidine derivatives called amidino carboxylic acids and their use as catalysts in Strecker reaction has been reported in the current work. The stability, local charge density and hydrogen bond parameters were calculated for eight derivatives with different substituents. In order to synthesize these amidino carboxylic acids, we initially prepared Knovenogel condensation products via the reaction of isatin derivatives with malonitrile. When the reaction was performed in water, the resulting nitrile groups of malonitrile derivatives was hydrolyzed with HOAC/ H2SO4 to generate the desired amide groups. The amide groups in resulting compound converted to amine groups with two Hoffman rearrangements in the presence of NaOH/Br2. Further neutralization led to the final zwitterionic α-amidino carboxylic acids. In the next step, the catalytic activity of these compounds as H-bond donor catalyst was investigated in Strecker reaction. The overall yields of the derivatives with substituent on the aromatic ring of starting isatins are higher than that for the overall yields of nitrogen-substituted isatins. The reaction of 5-nitro isatin with the next reagent gives lower yield in aryl-substituted products. An increase of catalytic activity is observed by rising the electron-withdrawing power of the aromatic ring substituents., The presence of nitro group in the structure of catalyst caused a large increase of catalytic activity in Strecker reaction. DFT calculations at B3LYP/6-31++g(d,p) and Lanl2dz level of theory showed that these compounds act as single H-bond catalysts and higher yields were obtained for complexes with stronger hydrogen bond. A simple and efficient method for synthesis of ɑ-amidino carboxylic acids was developed in this research. These compounds have been used as a single H-bond donor catalyst in the Strecker reaction. DFT calculations were carried out to confirm the experimental results. The obtained data from computations are in good agreement with experimental results.

Energetics, Ion, and Water Binding of the Unfolding of AA/UU Base Pair Stacks and UAU/UAU Base Triplet Stacks in RNA.

Triplex formation occurs via interaction of a third strand with the major groove of double-stranded nucleic acid, through Hoogsteen hydrogen bonding. In this work, we use a combination of temperature-dependent UV spectroscopy and differential scanning calorimetry to determine complete thermodynamic profiles for the unfolding of polyadenylic acid (poly(rA))·polyuridylic acid (poly(rU)) (duplex) and poly(rA)·2poly(rU) (triplex). Our thermodynamic results are in good agreement with the much earlier work of Krakauer and Sturtevant using only UV melting techniques. The folding of these two helices yielded an uptake of ions, Δ nNa+ = 0.15 mol Na+/mol base pair (duplex) and 0.30 mol Na+/mole base triplet (triplex), which are consistent with their polymer behavior and the higher charge density parameter of triple helices. The osmotic stress technique yielded a release of structural water, Δ nW = 2 mol H2O/mol base pair (duplex unfolding into single strands) and an uptake of structural water, Δ nW = 2 mol H2O/mole base pair (triplex unfolding into duplex and a single strand). However, an overall release of electrostricted waters is obtained for the unfolding of both complexes from pressure perturbation calorimetric experiments. In total, the Δ V values obtained for the unfolding of triplex into duplex and a single strand correspond to an immobilization of two structural waters and a release of three electrostricted waters. The Δ V values obtained for the unfolding of duplex into two single strands correspond to the release of two structural waters and the immobilization of four electrostricted water molecules.

DNA translocation through polyelectrolyte-modified nanopores: An analytical approximation.

An analytical model for the electrophoretic speed of DNA translocating through nanopore functionalized with polyelectrolyte (PE) brush is developed for the first time. The electrophoretic speed depends on DNA surface potential, applied electric field, viscosity, and permittivity of solution along with velocity and electrostatic potential at liquid-polyelectrolyte layer (PEL) interface where the interface seemed to behave similar to that of a solid-state nanopore wall. Under the limit of Debye-Hückel linearization, the electrostatic potential at liquid-PEL interface and at DNA surface have been calculated. Velocity at liquid-PEL interface has been estimated by assuming a linear variation of hydrodynamic frictional force within the PEL. It is observed that velocity and electrostatic potential at liquid-PEL interface strongly depend on PE charge density and softness parameter. Present analytical results show excellent agreement with exact numerical results (i.e., without any approximation) at a higher salt concentration where Debye-Hückel linearization is applicable.

Research of the JET A-1 aircraft fuel electrification

The paper presents the study of aviation fuel JET A-1 electrification and substantiation of the possibility to use static electricity for power generation. The modern aircraft refuelling with high-performance pumps followed by the fine filtration is a stable source of static charges generation, which raises the need to combat them. The results of the experiments show the dependence between the parameters of static charge density and the flow, flow rate, flow rate gradient and length of the pipeline. The level of the tank filling has been also accounted as a special index. We have also developed the device and the method for obtaining high voltage power, which is based on the positive use of the static electricity charges derived from the static charge converter. The further research must cover the effect of fuels electrification on the change of their operational properties, with the subsequent possibility of their modification.

Electrochemical Properties and Antibacterial Activity of Polyvinyl Chloride Supported Silver Molybdate Ion-Exchange Composite Membrane

Polyvinyl chloride supported silver molybdate composite material is used to develop by solution casting method. This membrane was characterized by various instrumental techniques such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analyses. These characterizations are used to understand the functional groups,thermal stability, surface morphology, porosity, ion transportation etc. The electrochemical study of membrane showed that the ionic potentials decrease by increasing the concentration of electrolyte solutions while the surface charge density of membrane followed the reverse order. It indicated that the membrane is showing negative charge property. Electrochemical parameters of membrane like surface charge density, transport number, mobility ratio, charge effectiveness etc are determined by TMS and Nernst theoretical equations.

Topological Structures in a Model Cuprate

We address a minimal model to describe the charge degree of freedom in the CuO2 planes with the on-site Hilbert space reduced to only a charge triplet of the three effective valence centers, nominally Cu1+;2+;3+, and made use of the S = 1 pseudospin formalism. The 2D S = 1 pseudospin system is prone to a creation of different topological structures which form topologically protected inhomogeneous distributions of the eight local S = 1 pseudospin order parameters including charge density and superfluid order parameters. We focus on the so-called quadrupole skyrmion which is believed to be a candidate for a topological charge excitation in parent or underdoped cuprates. Puzzlingly, such an unconventional structure is characterized by a uniform distribution of the mean on-site charge that makes the quadrupole skyrmion texture to be invisible for X-rays. We suppose that the parent insulating antiferromagnetic cuprates may be unstable with regard to nucleation of topological defects in the unconventional form of the one- or multi-center skyrmion-like object with ring-shaped superfluid regions.

Improving the performance of a numerical model to simulate the EHD interaction effect induced by dielectric barrier discharge

Over the past decade, there has been a growing interest in dielectric-barrier-discharge (DBD) plasma actuators. The lack of a general model to accurately simulate the related phenomena is one of the primary limitations in studying such type of actuators. One of the most frequently used models of this type was proposed by Suzen and Huang (S-H). Despite the numerous efforts made to improve this model, including a recent work of the authors, some deficiencies still exist.In this study, new modifications have been introduced to improve the performance and accuracy of the S-H phenomenological model. Here, a relation between the electrical-potential and charge-density equations has been made in the form of a boundary condition for charge distribution on the dielectric surface. Some semi-empirical relations are extracted for computing the plasma extension as well as the Debye length which is very important in simulation of the near-wall flow field. Furthermore, the one-equation for estimation of actuator-generated-thrust is corrected by these modifications. The main advantage of the modified model is that the model does not need to further calibration to predict accurately the Debye length, plasma extension and maximum charge density parameter in a range of voltages and frequencies. Promising results have been achieved in the simulation of the induced jet structures in the flat-plate boundary-layer for air as the working fluid.