Electron Density Distribution Research Articles

Bonding properties and crystal packing in β-(SeCl4)4 derived from Hirshfeld Atom Refinement.

Binary chalcogen halogen EX4 species represent intriguing systems in terms of chemical bonding theories, such as hypervalency and stereoactivity of lone electron pairs. Instead of a simple molecular EX4 structure, selenium tetrachloride forms an ionic pair, Cl3Se+Cl-, that assembles into a tetrameric (SeCl4)4 structure, namely, tetra-μ3-chlorido-dodecachloridotetraselenium. This article describes the charge-density analysis of the tetrameric molecule of β-SeCl4 based on the aspherical model obtained from Hirshfeld Atom Refinement of the tetrameric molecule and of an explicit cluster of 15 tetramers that simulates the crystal packing. Deformation density, electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) were used to evaluate the bonding situation, the electron-density distribution around the Se atom and the interaction energy of the tetramer.

Unsymmetric Protonation Driven Highly Efficient H2O2 Photosynthesis in Supramolecular Photocatalysts via One-Step Two-Electron Oxygen Reduction.

Photocatalytic hydrogen peroxide (H2O2) production has emerged as an attractive alternative to the traditional anthraquinone process. However, its performance is often hindered by low selectivity and sluggish kinetics of oxygen reduction reaction (ORR). Herein, we report an anthrazoline-based supramolecular photocatalyst, SA-SADF-H+, featuring an unsymmetric protonation structure for H2O2 photosynthesis from water and air.The introduction of unsymmetric protonation disrupts the initial mirror symmetry of SADF, significantly enhancing the molecular dipole and facilitating efficient charge separation and electron transfer. Additionally, this modification increases the hydrophilicity of SA-SADF-H+, enabling the interaction of water and dissolved oxygen with the catalytic sites. The altered electron density distribution creates numerous dual active sites for Yeager-type O2 adsorption, facilitating an efficient ORR towards H2O2 via a direct one-step two-electron pathway. Notably, SA-SADF-H+ achieves an outstanding photocatalytic H2O2 production at a rate of 4667 μmol L-1 h-1, with a remarkable solar-to-chemical conversion (SCC) of 1.35%, surpassing most organic photocatalytic systems. Furthermore, SA-SADF-H+ demonstrates remarkable photocatalytic antibacterial activity, achieving 100% antibacterial efficiency against Staphylococcus aureus within 60 min.

Investigation of the Binary Nitrides YN, LaN and LuN by Solid-State NMR Spectroscopy

Based on their various and outstanding properties, binary nitrides are used as (synthesis) materials in industry and research. Hence, their comprehensive characterization by analytical methods is of particular interest. Since Nuclear Magnetic Resonance (NMR) spectroscopy is very sensitive to the symmetry of the electronic density distribution, it is a suitable tool for the investigation of rock-salt structure types and, especially, for those with known stoichiometry issues. Here, we report on magic-angle spinning NMR spectra of the nuclides 89Y (I=12), 139La (I=72) and 14N (I=1) in polycrystalline samples of YN, LaN and LuN. Due to the high symmetry of their crystal structures, the spectra of all nuclides do not exhibit anisotropic effects of significant magnitude. The resulting isotropic chemical shift values are δiso(89Y) = 516 ppm for YN, δiso(139La) =1294 ppm for LaN, and δiso(14N) = 457 ppm (YN), 788 ppm (LaN) and 384 ppm (LuN). The newly determined δiso(14N) values for these three binary nitrides fit well into the previously reported linear correlation between nitrogen distance to the nearest cation and isotropic chemical shift, leading to a better correlation coefficient and reduced error margins for the fit parameters.

A New Method for Reconstruction of Regional Three‐Dimensional Electron Density Distributions Using AI‐Based Data Assimilation Method and Incoherent Scatter Radar Measurements

AbstractThe ionosphere's dynamic structure affects electromagnetic radiation by altering radio wave propagation, impacting daily communications. The characteristics of the ionosphere are primarily characterized by electron density parameters. This paper proposes a method to construct Three‐Dimensional (3‐D) electron density distributions with arbitrary spatiotemporal resolution in ISR observational regions. The method, termed Artificial Intelligence‐based data assimilation (AI‐Assim), integrates data assimilation directly into a neural network. It assimilates electron density from the IRI‐2020 model to fill ISR observation gaps. Experiments conducted using the Sanya Incoherent Scatter Radar (SYISR) in Hainan, China, successfully constructed a 3‐D electron density structure over the region, with a 0.2° latitude/longitude resolution and 1 km height resolution. The method's effectiveness was validated by calculating the mean square error and comparing the results with digisonde measurements.

The Relationship Between Spin Crossover (SCO) Behaviors, Cation and Ligand Motions, and Intermolecular Interactions in a Series of Anionic SCO Fe(III) Complexes with Halogen-Substituted Azobisphenolate Ligands.

To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5'-dihalogen substituents from fluorine to iodine were synthesized, and their anionic FeIII complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the FeIII complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C-H···X, C-H···N, and C-H···O hydrogen bonds, and C-H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity.

Deep Learning Model Size Performance Evaluation for Lightning Whistler Detection on Arase Satellite Dataset

The plasmasphere within Earth’s magnetosphere plays a crucial role in space physics, with its electron density distribution being pivotal and strongly influenced by solar activity. Very Low Frequency (VLF) waves, including whistlers, provide valuable insights into this distribution, making the study of their propagation through the plasmasphere essential for predicting space weather impacts on various technologies. In this study, we evaluate the performance of different deep learning model sizes for lightning whistler detection using the YOLO (You Only Look Once) architecture. To achieve this, we transformed the entirety of raw data from the Arase (ERG) Satellite for August 2017 into 2736 images, which were then used to train the models. Our approach involves exposing the models to spectrogram diagrams—visual representations of the frequency content of signals—derived from the Arase Satellite’s WFC (WaveForm Capture) subsystem, with a focus on analyzing whistler-mode plasma waves. We experimented with various model sizes, adjusting epochs, and conducted performance analysis using a partial set of labeled data. The testing phase confirmed the effectiveness of the models, with YOLOv5n emerging as the optimal choice due to its compact size (3.7 MB) and impressive detection speed, making it suitable for resource-constrained applications. Despite challenges such as image quality and the detection of smaller whistlers, YOLOv5n demonstrated commendable accuracy in identifying scenarios with simple shapes, thereby contributing to a deeper understanding of whistlers’ impact on Earth’s magnetosphere and fulfilling the core objectives of this study.

The Electron‐Density Distribution of UCl4 and Its Topology from X‐ray Diffraction

AbstractThe chemistry of electrons in actinide complexes and materials is still poorly understood and represents a serious challenge and opportunity for experiment and theory. The study of the electron density distribution of the ground state of such systems through X‐ray diffraction represents a unique opportunity to quantitatively investigate different chemical bonding interactions at once, but was considered “almost impossible” on heavy‐atom systems, until very recently. Here, we present a combined experimental and theoretical investigation of the electron density distribution in UCL4 crystals and comparison with the previously reported spin density distribution from polarized neutron diffraction. All approaches provide a consistent picture in terms of electron and spin density distribution, and chemical bond characterization. More importantly, the synergy between experiments and quantum‐mechanical calculations allows to highlight the remarkable sensitivity of X‐ray diffraction to electrons in materials.

Supramolecular Structure of Sulfonamide-Substituted Silatranes: Quantum Chemical DFT Calculations.

The supramolecular structure of the crystal products-N-[2-chloro-2-(silatranyl)ethyl]-4-nitro-benzenesulfonamide 4d and N-chloro-N-[2-chloro-1-(silatran-1-yl-methyl)ethyl]benzene-sulfonamide 5a was established by X-ray diffraction analysis data, FTIR spectroscopy and DFT quantum chemical calculations. Their crystal lattice is formed by cyclic dimers with intermolecular hydrogen NH∙∙∙O-Si bonds and CH∙∙∙O=S short contacts. The distribution of electron density in the monomers was determined using quantum chemical calculations of their molecular electrostatic potential (MESP) in an isolated state (in gas) and in a polar medium. The transition from covalent N-Si bonds in crystal compounds and polar medium to non-covalent N∙∙∙Si bonds happened while performing the calculations on the monomer molecules and their dimers in gas. The effect of intermolecular interactions on the strength of the N-Si and N∙∙∙Si bonds in molecules was evaluated through calculations of their complexes with H2O and DMSO.

Investigating the electronic properties and reactivity of polyaniline emeraldine base functionalized with metal oxides

Due to its appealing qualities, such as its miniature size and the ability to modify physical properties through chemical synthesis and molecular design, polymer material offers considerable advantages over traditional inorganic material-based electronics. Conjugate polymers are particularly interesting because of their molecular design capabilities, which enable the synthesis of conducting polymers with a variety of ionization potentials and electron affinities (EA), and their ability to control the energy gap and electronegativity (χ). Accordingly, density functional theory (DFT) at the B3LYP/SDD model was used to present possible interactions between polyaniline (PANi) and both alkali and heavy metal oxides. Total dipole moment (TDM), HOMO–LUMO band gap energy (ΔE), ionization energy (IE), EA, chemical hardness (η), chemical potential (μ), electrophilicity index (ω), chemical softness (S), and χ are calculated. TDM of PANi increased while ΔE decreased due to functionalization. The distribution of electronic charge density in molecular electrostatic potential (MESP) maps together with the results of ω reflected the electrophilic nature. The obtained results confirmed that the addition of metal oxides significantly improves the TDM, ΔE, and reactivity descriptors. A strong correlation between the experimental and calculated IR spectra was observed. Additionally, PANi–2MgO and PANi–2MnO model molecules exhibited the highest reactivity. Accordingly, PANi functionalized with MgO and MnO are promising candidates for energy storage devices.

Halogen substitution effects in Chlorostannate(II) hybrid material: Insights from DFT study on 2(C4H4FN3O)·SnX6·2(H2O), (X = F, Cl, Br, I)

The development of new materials is crucial for advancing technologies in material science, energy, and biology. In this study, we investigate the effect of Halogen-substitution on the compound 2(C4H4FN3O)·SnX6·2(H2O) (where X = F, Cl, Br, and I). Using extensive theoretical analysis, we examined the impact of halogen substitution on the structural properties, band gap energy (Eg), and chemical behavior. Our results show that the Eg decreases with the increasing atomic number of halogens. The I-substituted compound is the most reactive and exhibits significant intramolecular charge transfer, enhancing its antioxidant properties. The spatial distribution of electron density in the Frontier Molecular Orbitals (FMOs) indicates that the HOMO is localized on the inorganic anion and the LUMO on the organic cation, a pattern consistent across all substituted compounds. These findings highlight the potential of these compounds in electron transfer reactions and provide insights for tailoring them for specific chemical and biochemical applications.

Ab Initio Structure and Dynamics of Beryllium Monofluoride and Its Anion.

The accurate potential energy functions of beryllium monofluoride, BeF, and its anion, BeF-, have been determined from ab initio calculations using the coupled-cluster approach, up to the CCSDTQP level of approximation, in conjunction with the augmented correlation-consistent core-valence basis sets, aug-cc-pCVnZ, up to septuple-zeta quality. The vibration-rotation energy levels of the two species were predicted to near the "spectroscopic" accuracy. Changes in the electron density distribution upon formation of the Be-F chemical bond are discussed.

Features of electronic structure of (<i>η</i>⁵-C₅H₅)LuCl₂(THF)₃

For the first time, a topological analysis of the electron density distribution function in a crystal for an organolanthanide compound was carried out using the CpLuCl₂(THF)₃ complex as an example. The charges on atoms were determined. A predominantly ionic nature of the Lu–ligand bond was confirmed, but the essentially covalent nature of the Lu–Cp bond was discovered. The energies of the Lu–ligand bonds were determined.

All-optical method for generating transient microstructured targets in laser ion acceleration

We demonstrate an all-optical method that online produces “microstructured” targets by manipulating a Laguerre-Gaussian (LG) prepulse. Besides the enhancement of the proton number, the cutoff energy is nearly doubled. Such transient “microstructured” targets are characterized using both offline and online approaches. Based on probe experiments and hydrodynamic simulations, we develop a simple model to describe the electron density distribution upon the arrival of the main pulse. Two-dimensional particle-in-cell simulations reveal that the annular plasma acts as an oscillating cavity for hot electrons and results in a cascaded acceleration effect. The combination of low-intensity LG prepulses and ultraintense Gaussian pulses opens another avenue for fine-tuning laser-plasma interactions spatiotemporally in interdisciplinary applications. Published by the American Physical Society 2024

Experimental and Theoretical Characterization of 4π‐Electron Möbius Aromatic System of a 1,2‐Digermacyclobutadiene†

AbstractWe present the visualization of the experimental valence electron‐density distribution (EDD) in the isolated 1,2‐digermacyclobutadiene ring system, revealing the unique 4π electron‐delocalization on the four‐membered Ge2C2 ring. A remarkably high Möbius 4π‐electron aromatic character in the Ge2C2 ring can be suggested from theoretical calculations, in sharp contrast to the significant antiaromaticity of the all‐carbon cyclobutadiene ring.

Distinctive features of measuring <I>T<SUB>e</SUB></I> and <I>n<SUB>e</SUB></I> spatial distributions in the Globus-M2 spherical tokamak using method of Thomson scattering of laser radiation

The results of measuring the electron temperature and density spatial distributions in plasma of the Globus-M2 tokamak using the Thomson scattering diagnostics are presented. The diagnostics provides measurements throughout the entire tokamak discharge, starting from time of gas breakdown. The Thomson scattering data were analyzed in order to determine the positions of the last closed flux surface, the plasma magnetic axis, and the radius of inversion during the saw-tooth oscillations. The results of measurements performed during the internal reconnection of magnetic field lines are presents, as well as the dynamics of spatial distributions of electron temperature, density and pressure during the plasma transition to the H-mode. The results of measuring the electron temperature distribution in the scrape-off layer using the Thomson scattering diagnostics are also presented for distances up to 4 cm outside the last closed flux surface.

Convolutional network learning of self-consistent electron density via grid-projected atomic fingerprints

The self-consistent field (SCF) generation of the three-dimensional (3D) electron density distribution (ρ) represents a fundamental aspect of density functional theory (DFT) and related first-principles calculations, and how one can shorten or bypass the SCF loop represents a critical question in electronic structure theory from both practical and fundamental standpoints. Herein, a machine learning strategy, DeepSCF, is presented in which the map between the SCF ρ and the initial guess density (ρ0) constructed by the summation of neutral atomic densities is learned using 3D convolutional neural networks (CNNs). High accuracy and transferability of DeepSCF are achieved by first encoding ρ0 on a 3D grid and then expanding the input features to include atomic fingerprints beyond ρ0. The prediction of the residual density (δρ) rather than ρ itself is targeted, and given that δρ is indicative of chemical bonding information, a dataset of small-sized organic molecules featuring diverse bonding characters is adopted. The fidelity of DeepSCF is finally enhanced by subjecting the atomic geometries of the dataset to random rotations and strains. The effectiveness of DeepSCF is demonstrated using a complex carbon nanotube-based DNA sequencer model. This work evidences that the nearsightedness in electronic structure can be optimally represented via the spatial locality in CNNs, offering insight into the success of various machine learning-based atomistic materials simulations.

Catalytic behavior, electronic structure and spectroscopic (FT-IR, Raman, UV–vis) properties for the new ionic liquid imidazolium hydrogen sulfate

Catalytic performance, chemical reactivity, vibrational modes and electronic transitions of the ion pair [H–Im]+[HSO4]– were investigated in the current paper. Hence, a combined experimental (Hammett acidity function, infrared, Raman and ultraviolet-visible spectroscopies) and theoretical (molecular electrostatic potential surface, reduced density gradient, frontier molecular orbital analysis, quantum theory of atoms in molecules, net atomic charges, global and local reactivity descriptors) study was conducted. In terms of the catalytic performance, the acetic acid esterification with butanol was evaluated. Important kinetic (rate constant, activation energy, pre-exponential factor) and thermodynamic (enthalpy, entropy, Gibbs free energy barrier) factors for ester production as a function of the temperature and catalyst loading have been determined. Results revealed intensive electron density distribution in [H–Im]+[HSO4]– due to chemical interactions between the cationic and anionic moieties. These bonds were established as electrostatic in nature. The pronounced charge transfers within [H–Im]+[HSO4]– managed the title compound acidity (H0) and its catalytic behavior towards butyl acetate synthesis. Using the thermodynamic and kinetic measurements, a mechanism for acetic acid esterification with butanol in the presence of imidazolium hydrogen sulfate ionic liquid was offered.

Achieving High OER Performance by Tuning the Co/Mn Content in Prussian Blue Analogues.

The need for efficient, economical, and clean energy systems is increasing, and as a result, interest in water-splitting techniques to produce green hydrogen is also increasing. However, the sluggish kinetics of the oxygen evolution reaction (OER) hinders the practical application and widespread use of water-splitting technologies; therefore, to address this challenge, it is essential to develop cost-effective and efficient OER catalysts. In this work, we have synthesized an inexpensive and tunable FeCoMn Prussian blue analogue (PBAs) as an efficient OER catalyst via a straightforward process. The ratio of the Co and Mn to optimize the electrochemical performance, and as a result, the FeCo0.41Mn0.42 PBA catalyst demonstrated the best electrochemical performance (260/304 mV overpotential at 10/50 mA cm-2, a low Tafel slope of 48 mV dec-1 and a good stability of 72 h at 10 mA cm-2). Additionally, X-ray absorption spectroscopy (XAS) measurements and density functional theory (DFT) calculations suggest that the FeCo0.41Mn0.42 PBA possesses the optimized electronic density distribution at the active site (Co), and the doping of Mn and Fe can not only increase the electricity conductivity but also activate the critical H2O deprotonation step.

Electronic, thermodynamic, NLO, and spectroscopic properties of OAFLC compounds via DFT: A focus on 1F6B, 1F6Bi, 1F6BiN, and 1F6BN

This study presents a comprehensive quantum mechanical investigation of four novel liquid crystalline compounds: 1F6B, 1F6Bi, 1F6BiN, and 1F6BN. Using Density Functional Theory (DFT) with the B3LYP functional and 6-311G(d,p) basis set, we optimized the molecular geometries and analyzed their electronic and vibrational properties. Atomic Polar Tensor (APT) charge analysis showed significant charge distributions. Electrostatic potential (ESP) mapping identified potential reactive sites, while Electron Localization Function (ELF) and Localized Orbital Locator (LOL) analyses depicted the electron density distributions. Thermodynamic parameters indicated the compounds’ vibrational stability and responsiveness to thermal changes. Non-linear optical (NLO) properties were characterized by significant dipole moments and polarizabilities, suggesting potential in optoelectronic applications. Frontier molecular orbital analysis indicated stability with HOMO-LUMO gaps ranging from 4.15 to 4.64 eV. UV–Vis spectra revealed key electronic transitions, while Raman spectroscopy detailed various vibrational modes. The study offers valuable insights into the molecular behavior of these compounds, laying the groundwork for their future applications in material science and advanced technologies.

Electronic and photocatalytic properties of Cu4 cluster-modified Ag/g-C3N4 single-atom catalysts: A hybrid DFT study

Increasing the active sites on the catalyst surface has been a key goal to increase the catalyst efficiency. This paper presents an efficient conversion of solar energy into chemical energy, realized by a Cu4 cluster-assisted single-atom catalyst (Ag-doped g-C3N4). The catalyst enhances charge transfer and light absorption, and the unique advantages of this approach in the field of photocatalysis are substantiated by density functional theory. Under the synergistic effect of Cu4 clusters, the electronic state density distribution of the Ag single-atom catalyst substrate is drastically altered, which realizes the increase of substrate active sites and rapid charge separation and transfer. Compared with the pristine substrate g-C3N4, the new electronic state distribution and the generation of impurity energy levels lead to the narrowing of the band gap from 2.77 to 1.83 eV, accelerating the transfer and separation of electrons and holes, and enlarging the visible light absorption range from 410 to 760 nm, thus improving the solar energy utilization. Despite the reduced band gap, the conduction and valance band edges of (Ag, Cu4) codoped g-C3N4 still have sufficient potential to split water. Therefore, to improve the photocatalytic performance under visible light, simultaneous codoping of the Ag single atom and Cu4 cluster on g-C3N4 is an effective strategy. The study provides theoretical support for further optimization of single-atom catalysts.