Repulsive Region Research Articles

Synthesis, crystal structure, Hirshfeld surface analysis, NCI-RDG, molecular docking, molecular dynamic simulations, and toxicity assessment of 2-((2, 4-dimethoxybenzylidene) hydrazono) -1, 2-diphenylethanone

This study reports the synthesis of a hydrazone-like compound with the chemical formula C23H20N2O3. The synthesis involved reacting benzilmonohydrazone with 2,4-dimethoxybenzaldehyde at 85°C for 3 hours. The mixture was cooled, filtered, and washed with ethanol. The resultant solid was then recrystallized in a suitable solvent to isolate the desired product. To investigate the molecular geometrical properties of the 2-(2, 4-dimethoxybenzylidene) hydrazone)-1, 2-diphenylethanone (DBHDE) molecule, both theoretical and experimental methods were employed. Density functional theory (DFT) calculations using the B3LYP functional and a 6-311G (d, p) basis set were performed, and the calculated geometric parameters showed good agreement with the experimental data. In addition, Hirshfeld surface analysis and 2D fingerprint plots indicated that the most significant intermolecular interactions in the crystal packing of DBHDE are H...H (48.8%) and C...H/H...C (28.4%). According to NCI-RDG analysis, the centers of the three benzene rings represent the highest repulsive interaction regions in the molecule. Finally, the biological potential of the synthesized compound was thoroughly evaluated using molecular docking studies, molecular dynamics simulations, in silico ADME-T investigation, and biochemical analyses (cholesterol, creatinine and transaminases) in wistar rats.

Study of Sterically Crowded Alkanes: Assessment of Non-Empirical Density Functionals Including Double-Hybrid (Cost-Effective) Methods.

We theoretically study here the homolytic dissociation reactions of sterically crowded alkanes of increasing size, carrying three different (bulky) substituents such as tert-butyl, adamantyl, and [1.1.1]propellanyl, employing a family of parameter-free functionals ranging from semi-local, to hybrid and double-hybrid models. The study is complemented with the interaction between a pair of HC(CH3)3 molecules at repulsive and attractive regions, as an example of a system composed by a pair of weakly bound sterically crowded alkanes. We also assessed the effect of incorporating reliable dispersion corrections (i. e., D4 or NL) for all the functionals assessed, as well as the use of a tailored basis set (DH-SVPD) for non-covalent interactions, which provides the best trade-off between accuracy and computational cost for a seemingly extended applications to branched or crowded systems. Overall, the PBE-QIDH/DH-SVPD and r2SCAN-QIDH/DH-SVPD methods represent an excellent compromise providing relatively low, and thus very competitive, errors at a fraction of the cost of other quantum-chemical methods in use.

Study of self-assembly between two magnetic particle chains in magnetorheological fluids

The self-assembly behavior of individual magnetic particles in magnetorheological liquids has been extensively analyzed in previous studies, but the self-assembly behavior between chains of magnetic particles has rarely been investigated. In this paper, the self-assembly mechanism between chains of magnetic particles is investigated using simulation and experimental methods. Firstly, a two-dimensional coupling simulation numerical model of particle-magnetic field-flow field is constructed by analyzing the magnetic force, fluid force and contact interaction force between magnetic particles. The accuracy of the simulation model was verified through experiments. Then the attraction and repulsion dividing line of two magnetic particle chains are analytically calculated by simulation combined with parametric scanning. And analyze the law of the influence of the number of magnetic particles between magnetic particle chains on the attraction and repulsion dividing line. Finally, the different self-assembly behaviors that occur when magnetic particle chains are in different regions of attraction and repulsion between them are experimentally verified. Thus, this study provides new insights into the self-assembly mechanism between chains of magnetic particles in magnetorheological fluids in terms of the effect of the number of magnetic particles on the attraction–repulsion dividing line.

Manifestation of the normal intensity distribution law (NIDL) in the rovibrational emission spectrum of hydroxyl radical

The latest experimental [Noll et al. Atmos. Chem. Phys. 20, 5269 (2020)] and theoretical [Brooke et al. J. Quant. Spectr. Rad. Transfer 168, 142 (2016)] data on the OH emission intensities are analysed with use of the NIDL. It is found that the calculated intensities of the Δ v > 6 transitions should not be trusted. The analysis of the OH data revealed that the NIDL theory is not applicable to the satellite bands. The effect of small reduced mass previously discovered in H 2 [Ushakov et al. J. Mol. Spectrosc. 399, 111863 (2024)], causing the NIDL straight-line slope to be larger than the one associated with the repulsive branch of the potential, is demonstrated in OH, and the same should be true of all the diatomic hydrides. We performed ab initio calculations of the OH repulsive branch and compared it with the one of Brooke et al. and the other due to Varandas and Voronin [Chem. Phys. 194, 91 (1995)]. We found that the ab initio PEF closely follows the Varandas-Voronin potential in the repulsive region important for calculating the overtone intensities [Medvedev, J. Chem. Phys. 137, 174307 (2012)].

Repulsive gravity in regular black holes

We evaluate the effects of repulsive gravity using first order geometric invariants, i.e. the Ricci scalar and the eigenvalues of the Riemann curvature tensor, for three regular black holes, namely the Bardeen, Hayward, and Dymnikova spacetimes. To examine the repulsive effects, we calculate their respective onsets and regions of repulsive gravity. Afterwards, we compare the repulsive regions obtained from these metrics among themselves and then with the predictions got from the Reissner–Nordström and Schwarzschild–de Sitter. A notable characteristic, observed in all these metrics, is that the repulsive regions appear to be unaffected by the mass that generates the regular black hole. This property emerges due to the invariants employed in our analysis, which do not change sign through linear combinations of the mass and the free coefficients of the metrics. As a result, gravity can change sign independently of the specific values acquired by the mass. This conclusion suggests a potential incompleteness of regular solutions, particularly in terms of their repulsive effects. To further highlight this finding, we numerically compute, for the Reissner–Nordström and Schwarzschild–de Sitter solutions, the values of mass, M, that emulate the repulsive effects found in the Bardeen and Hayward spacetimes. These selected values of M provide evidence that regular black holes do not incorporate repulsive effects by means of the masses used to generate the solutions themselves. Implications and physical consequences of these results are then discussed in detail.

A study on the extension of correlation functions obtained from molecular dynamics simulations by the Ornstein–Zernike theory for modeled molten salts

We extend the correlation functions obtained by molecular dynamics (MD) simulation for a molten salt modeled as a superposition of the Lennard-Jones (LJ) and Coulomb potentials using the hybrid closure method, which employs the Ornstein–Zernike (OZ) theory coupled with a closure relation. An appropriate distance for switching the short-range MD part and the long-range OZ part is determined by monitoring the isothermal compressibility, excess internal energy, and pressure. The Kobryn–Gusarov–Kovalenko (KGK) closure relation is mainly employed for the hybrid closure method (MD–KGK hybrid closure). The hybrid closure with either the hypernetted chain (HNC) or Kovalenko–Hirata (KH) closure was also tested to confirm that the performance was almost equivalent to one another among the MD–HNC, MD–KH, and MD–KGK methods. The bridge function for the model molten salt is extracted using the MD–KGK hybrid closure method. At a high-density state, the bridge function shows a steep increase in the repulsive core region, as is often observed for simple fluids, whereas when the density is relatively low, the bridge function for the cation–anion pair shows a downward-sloping behavior. Furthermore, the accuracies of excess internal energy, pressure, and isothermal compressibility were also examined for the HNC, KH, and KGK approximations. For molten salt systems, these approximations exhibited a similar behavior to those for monatomic LJ fluids, especially in the high-density state. The analysis of the integrand for excess internal energy and pressure is also discussed.

Insight into (Z)-ethyl-2-(2-((E)-2,4-dinitro benzylidene amino)-4-oxo-3-phenylthiazolidin-5-ylidene) acetate in-silico anti-SARS-CoV-2 performance: Synthesis, structural-spectral characterizations and DFT computations

This study reports on the synthesis of a 4-thiazolidinone derivative (EN2Th), namely, (Z)-Ethyl-2-(2-((E)-2,4-dinitro benzylidene amino)-4-oxo-3-phenylthiazolidin-5-ylidene) acetate. Its crystal structure has been determined by single crystal X-ray diffraction and the spectral characterizations were carried out by means of 1H and 13C NMR, and FT-IR techniques. The molecule of EN2Th crystallizes in the monoclinic P21/c symmetry and its crystal structure consists of a herringbone packing along [100]. The density functional theory (DFT) at the B3LYP/6-311G (d,p) level has been employed for structure optimization, the results confirm a good consistency between the theoretical and the experimental geometrical data. Hirshfeld surface and 2D fingerprints indicate C−H···O (29.7%) and H···H (24.5%) as the most relevant intermolecular interactions in the crystal packing of EN2Th. According to the reduced density gradient (RDG) analysis, EN2Th exhibits vdW to weak repulsive regions with low electron densities. The theoretical electronic circular dichroism (ECD) spectrum displays an exciton coupled transitions associated with the Z-configuration of the thiazolidin-4-one moiety reflecting the steric effect of the ester group. Charge transfer inside the 4-thiazolidinone derivative EN2Th was considered via the frontier molecular orbitals (FMOs) and natural bond orbital (NBO) investigations along with molecular electrostatic potential (MEP) distribution maps. The HOMO and LUMO energies allowed the estimation of the chemical reactivity descriptors. In accordance with the NBO results, the predicted hyperpolarizabilities indicate a strong donor to acceptor π-electrons delocalization in EN2Th. The anti-viral performance of EN2Th was evaluated in silico against SARS-CoV-2 main protease (MPro) via molecular docking simulations. Finally, ADMET (absorption, distribution, metabolism, excretion and toxicity) online software tools were utilized to uncover the title compound's potential cytotoxicity.

Cyclotetrabenzil Derivatives for Electrochemical Lithium‐Ion Storage

AbstractOrganic electrode materials could revolutionize batteries because of their high energy densities, the use of Earth‐abundant elements, and structural diversity which allows fine‐tuning of electrochemical properties. However, small organic molecules and intermediates formed during their redox cycling in lithium‐ion batteries (LIBs) have high solubility in organic electrolytes, leading to rapid decay of cycling performance. We report the use of three cyclotetrabenzil octaketone macrocycles as cathode materials for LIBs. The rigid and insoluble naphthalene‐based cyclotetrabenzil reversibly accepts eight electrons in a two‐step process with a specific capacity of 279 mAh g−1 and a stable cycling performance with ≈65 % capacity retention after 135 cycles. DFT calculations indicate that its reduction increases both ring strain and ring rigidity, as demonstrated by computed high distortion energies, repulsive regions in NCI plots, and close [C⋅⋅⋅C] contacts between the naphthalenes. This work highlights the importance of shape‐persistency and ring strain in the design of redox‐active macrocycles that maintain very low solubility in various redox states.

Cyclotetrabenzil Derivatives for Electrochemical Lithium-Ion Storage.

Organic electrode materials could revolutionize batteries because of their high energy densities, the use of Earth-abundant elements, and structural diversity which allows fine-tuning of electrochemical properties. However, small organic molecules and intermediates formed during their redox cycling in lithium-ion batteries (LIBs) have high solubility in organic electrolytes, leading to rapid decay of cycling performance. We report the use of three cyclotetrabenzil octaketone macrocycles as cathode materials for LIBs. The rigid and insoluble naphthalene-based cyclotetrabenzil reversibly accepts eight electrons in a two-step process with a specific capacity of 279 mAh g-1 and a stable cycling performance with ≈65 % capacity retention after 135 cycles. DFT calculations indicate that its reduction increases both ring strain and ring rigidity, as demonstrated by computed high distortion energies, repulsive regions in NCI plots, and close [C⋅⋅⋅C] contacts between the naphthalenes. This work highlights the importance of shape-persistency and ring strain in the design of redox-active macrocycles that maintain very low solubility in various redox states.

Investigation of Contact Electrification between 2D MXenes and MoS2 through Density Functional Theory and Triboelectric Probes

AbstractContact electrification (triboelectrification) (CE) is a universal phenomenon in ambient environment and has been recorded for more than 2600 years. Nonetheless, the intrinsic mechanism of CE still remains controversial. Herein, based on first‐principles theory, the underlying mechanism in CE is systematically investigated between metallic MXenes and semiconductive MoS2. The results show that the work functions of contacting materials dominate the direction of electron transfer during CE process. That is, the electron will be transferred from the material with low work function to the one with high work function. The theoretical prediction is verified experimentally through investigating triboelectric probes based on MXenes and MoS2 nanomaterials. Additionally, it is noted that the interfacial potential barrier and the work function difference together modulate the amount of transferred electron. Electron transfer mainly occurs in the repulsive forces region where the interaction distance between the two materials is shorter than the normal bonding length. The quantum calculation results agree well with the Wang transition theory. Furthermore, it is also noticed that, due to the wave‐particle duality of electron, electron transfer will obviously occur at the attractive force region when the two contacting materials exhibit a larger work function difference.

The elastic scattering cross sections of the N[formula omitted]-H and N-H[formula omitted] collisions for the transport theory

The transport cross sections and integrated cross sections are calculated for interactions of hydrogen and nitrogen atoms and ions (in the ground and excited states) for use in plasma science and hypersonic flows theory. The data for the transport cross sections are given in the energy range typically needed (or broader) for those applications: 10−6-37 hartree (around 2.7⋅10−5eV-1 keV). The reported cross sections are calculated from the high quality ab initio potential energy curves with additional extrapolation for highly repulsive region. The methods and energy range are discussed in the context of LXCat and IAEA (ALADDIN and CollisionDB) databases. The uncertainty of data is also estimated.

Stress accumulation versus shape flattening in frustrated, warped-jigsaw particle assemblies

Geometrically frustrated assembly has emerged as an attractive paradigm for understanding and engineering assemblies with self-limiting, finite equilibrium dimensions. We propose and study a novel 2D particle based on a so-called ‘warped jigsaw’ (WJ) shape design: directional bonds in a tapered particle favor curvature along multi-particle rows that frustrate 2D lattice order. We investigate how large-scale intra-assembly stress gradients emerge from the microscopic properties of the particles using a combination of numerical simulation and continuum elasticity. WJ particles can favor anisotropic ribbon assemblies, whose lateral width may be self-limiting depending on the relative strength of cohesive to elastic forces in the assembly, which we show to be controlled by the range of interactions and degree of shape misfit. The upper limits of self-limited size are controlled by the crossover between two elastic modes in assembly: the accumulation of shear with increasing width at small widths giving way to unbending of preferred row curvature, permitting assembly to grow to unlimited sizes. We show that the stiffness controlling distinct elastic modes is governed by combination and placement of repulsive and attractive binding regions, providing a means to extend the range of accumulating stress to sizes that are far in excess of the single particle size, which we corroborate via numerical studies of discrete particles of variable interactions. Lastly, we relate the ground-state energetics of the model to lower and upper limits on equilibrium assembly size control set by the fluctuations of width along the ribbon boundary.

Anomalous layer-dependent lubrication on graphene-covered substrate: Competition between adhesion and plasticity

Friction on samples covered by few-layer graphene is well known to exhibit the unique layer dependence where friction measured by atomic force microscopy at the nanoscale is generally observed to decrease with the increasing number of layers. However, this trend is not always observed in experiments and simulations for tips comprised of different materials and for graphene on different substrates. Within this context, the exact role played by the interface, in particular graphene-tip/graphene-substrate adhesion and substrate plasticity, in the layer dependence of friction on graphene is not yet fully understood. We conduct molecular dynamics simulations to probe the evolution trend of the layer dependence with high interfacial adhesion under varied external normal loads. To better evaluate the frictional quality, we divide the contact interface into the adhesive and repulsive regions, and the total wrinkle variation is decomposed into the sum of dimple depth and pucker height. In the low load stage, contrary to the traditional perception, higher friction is observed in the bilayer system than that in the monolayer case. However, the bilayer system performs better in lubrication and wear protection when the load reaches high enough to induce plasticity in substrates. Theanomalous layer-dependentfrictional behavior originates from the interplay among interfacial adhesion, wrinkle of topmost graphene, contact roughness, and plastic deformation of substrates. We further corroborate our conclusion via the comparison with the case employing amorphous silicon substrates. In addition to surface roughness, out-of-plane deformation, and electron–phonon coupling, interfacial adhesion and substrate plasticity play pivotal roles in tribological performance and require extra considerations in designing lamellar lubricants such as two-dimensional materials.

Time-varying formation tracking for noisy multi-agent systems with unknown leader trajectory

In this article, time-varying formation tracking problem for multi-agent systems is investigated. It is assumed the number of agents is changing and obstacles should be avoided along the trajectory. In addition, the tracking formation should be reached while the leader trajectory is unknown and communication data are noisy. To reach the desired formation tracking, first, a virtual leader is constructed using the local neighbouring data. Second, the reference signal is created based on the virtual leader and the leader data (which is available for some agents). The data fusion at this stage is done based on Kalman filtering to reduce the effect of communication noise. Third, an integral state feedback controller as a new consensus formation controller based on the relative position and velocity vectors of the agents and the estimated (virtual) leader are proposed to achieve the time-varying formation tracking. Next, closed-loop stability of the system under the proposed control law is investigated using the Lyapunov stability theorem. In order to implement the proposed control strategy, an extended state observer is designed to estimate the required velocity and accelerations. Finally, an obstacle avoidance strategy would be embedded to the controller via a repelling strategy. That is, once the leader identifies the obstacle and enters a repulsion region, its reference trajectory is modified to keep a safe distance from the obstacle. The agents modify their reference trajectory according to the new leader trajectory while trying to keep their formation. As an illustrative example, various simulations are performed for formation tracking of a unmanned aerial vehicle multi-agent system to evaluate its performance.

Strange attractors and nontrivial solutions in games with three players

Two-player games have been sufficiently researched, but three-player games have a much greater wealth of solutions, in particular, nonstationary solutions. However, unsteady solutions of three-player games have not been studied in the literature. On the basis of numerical modeling, the dynamic behavior of a 2 × 2 × 2 game with three players is investigated in the range of payoff matrices from -1 to 1. The system of dynamic equations includes three variables (probabilities of pure strategies) and twelve parameters associated with cubic payoff matrices of players. The phase space of a three-player game is a cube (probabilities vary from 0 to 1). It was found that for some payoff matrices, there are no stable solutions in the system. In addition, the structure of the phase space is complex: the volume of the cube is a fractal repulsive region from which the phase trajectories leave, a strange attractor is located near the edge corresponding to the solution of the "node-center" type, and another strange attractor is a chaotic motion between adjacent vertices of the cube. The obtained dynamic properties of the game can be used for making decisions in economics, negotiations between three persons, and modeling relationships between biological species.

On-the-Fly Ring-Polymer Molecular Dynamics Calculations of the Dissociative Photodetachment Process of the Oxalate Anion.

The dissociative photodetachment dynamics of the oxalate anion, C2O4H− + hν → CO2 + HOCO + e−, were theoretically studied using the on-the-fly path-integral and ring-polymer molecular dynamics methods, which can account for nuclear quantum effects at the density-functional theory level in order to compare with the recent experimental study using photoelectron–photofragment coincidence spectroscopy. To reduce computational time, the force acting on each bead of ring-polymer was approximately calculated from the first and second derivatives of the potential energy at the centroid position of the nuclei beads. We find that the calculated photoelectron spectrum qualitatively reproduces the experimental spectrum and that nuclear quantum effects are playing a role in determining spectral widths. The calculated coincidence spectrum is found to reasonably reproduce the experimental spectrum, indicating that a relatively large energy is partitioned into the relative kinetic energy between the CO2 and HOCO fragments. This is because photodetachment of the parent anion leads to Franck–Condon transition to the repulsive region of the neutral potential energy surface. We also find that the dissociation dynamics are slightly different between the two isomers of the C2O4H− anion with closed- and open-form structures.

Theoretical investigation on influence of protic and aprotic solvents effect and structural (Monomer, Dimer), Van-der Waals and Hirshfeld surface analysis for clonidine molecule

The protic (water, Ethanol) and aprotic (DMSO) solvent effect on clonidine molecule were investigated by theoretically using DFT/B3LYP method with 6-311 g++(d,p) as a basis set and IEFPCM model. Potential energy surface analysis was carried out for detecting minimum and maximum energy structure. The monomer and dimer structure were optimized and compared geometrical parameters like bond length and angle. Influence of Solvents have been investigated electronic spectral analysis, orbital analysis and reactive site identification as well as hyperpolarizability investigation. Hydrogen bonding attractive and steric repulsive regions are identified by non-covalent interaction (NCI) investigation. Inter and intra molecular interactions are identified by using Hirshfield analysis in various modes.

Numerical simulation for magnetic field analysis and magnetic adsorption behavior of ellipse magnetic matrices in HGMS: Prediction magnetic adsorption behavior via numerical simulation

Magnetic matrices are the core components of HGMS systems. In this study, the induced magnetic field distribution characteristics of ellipse magnetic matrices are investigated via numerical simulation. Besides, the effects of magnetic matrices structure parameters and magnetic field distribution characteristics on the cumulative adsorption behavior of magnetic particles are also discussed. First, the numerical simulation results indicated that compared with the simulation results of a single magnetic matrix, the multi-matrix composite system simulation results demonstrate that an interaction of the induced magnetic fields generated by the superposition of magnetic fields is enhanced with the increase in the long axis size or the decrease in the gap between the matrices, heightening the magnetic induction but leading to the magnetic field gradient and magnetic field forces to significantly decrease near the surface of the matrix. And the rapid reduction of the magnetic field forces around the single matrix leads to a reduction in the range of action. However, to a certain extent, the interaction of the induced magnetic fields also will make the scope of the magnetic field force expand with the decrease in the gap between the matrices. The magnetic cumulative adsorption tests prove that it is feasible to infer the adsorption behavior of magnetic particles through the numerical simulation and theoretical calculations. The adsorption morphology of magnetic particles on the surface of magnetic matrices show that the repulsive region of magnetic particles is perpendicular to the direction of magnetic field, and the adsorption region of magnetic particles is parallel to the direction of magnetic field and with the increase of the size of magnetic matrices, the effective adsorption area of magnetic particles on the surface of magnetic matrices decreases gradually. Besides, with the increase of the horizontal gap between adjacent magnetic matrices, the adsorption thickness of magnetic particles on the surface of magnetic matrices decreases. Moreover, with the expansion of the horizontal gap between the adjacent magnetic matrices, the adsorption amount of the magnetic particles gradually decreases due to the decrease of the adsorption area and fill rate. The adsorption amount of magnetic particles will decrease as the long axis size increases when the fill rate of the magnetic matrices is similar.

Repulsive, Densely Packed Ligand-Shells Mediate Interactions between PbS Nanocrystals in Solution

The surface capping ligands on nanocrystals (NCs) impart colloidal stability and determine the organization into ordered solids when cast from solution. Here, we use small-angle neutron scattering (SANS) to measure the solution structure factor in dispersions of fully passivated, oleate-capped PbS NCs up to concentrations of 16 v/v%. Fitting the data by assuming an attractive square well interaction potential between NCs yields a repulsive core diameter larger than the physical NC core diameter. This repulsive core stems from a densely packed region of the ligand-shell near the NC surface. The spatial extent of the repulsive core increases with temperature as ligand motion increases, becoming repulsive farther out in the ligand-shell, while the portion of ligand-shell outside of the repulsive region remains attractive with a strength of ∼1 kBT. SANS provides a molecular interpretation of the fundamental interparticle interactions in colloidal nanocrystal suspensions, ultimately relevant to understanding the self-organization of nanoscale materials.

Relativistic treatment of alkaline earth dimers in the presence of non-central molecular potential in N-dimensions

Abstract Within the framework of relativistic theory, N-dimensional non-central Morse potential as anharmonic model is considered thoroughly to describe the internuclear motion of alkaline earth dimers in the different electronic states. We illustrate the surface plots of alkaline earth dimers to examine the effect of angular potential, due to existence of molecular systems in which spherical symmetry disappears. Also, the contribution of angle dependent interaction to the relativistic energy spectra has been investigated in N-dimensions. We determine the relativistic vibrational transition frequencies in the lower vibrational states for the X 1 Σ g + ground state of 24 Mg 2 , 40 Ca 2 , 24 Mg 40 Ca and A 1 Σ u + excited state of 88 Sr 2 alkaline earth diatomic molecules. The theoretical results have been compared with Rydberg-Klein-Rees (RKR) and the inverted perturbation approach (IPA) experimental data. We also discussed the validity of Pekeris approximation around the equilibrium distance as well as the repulsive and attractive regions for alkaline earth dimers.