Electronic Charge Distribution Research Articles

Computational and experimental investigations on structural, electronic and optical properties of scheelite compounds

Oxide of tungstate has consistently been pursued for use in optoelectronic applications. This study details the synthesis of AWO4 (A = Ba, Sr and Ca) using a high-temperature solid-state method. Additionally, theoretical calculations highlight its electronic structure, density of states, photoelectric properties, and vibrational modes. The x-ray diffraction of AWO4 (A = Ba, Sr and Ca) was meticulously introduced by the utilization of Rietveld for refinement. The refined lattice parameters substantially verified AWO4 (A = Ba, Sr and Ca) as a tetragonal system of scheelite with the spatial group of I41/a, and demonstrated significant alteration with the discrepancy in the radius of alkaline earth metal (A-site) ions. The electronic configuration and optical attributes of AWO4 (A = Ba, Sr and Ca) possessing scheelite-like structure were explored using density functional theory (DFT) based computational techniques. The theoretical blueprint was derived by optimizing the structure based on defects. The postulated optical bandgap energy confirms the occurrence of direct electronic transitions at Brillouin region G points. Calculations suggested the direct band gaps of BaWO4, SrWO4, and CaWO4 at 4.385, 3.123 and 3.813 eV. This was attributed to the energy levels produced by O and A-site atoms in the valence band, and W and O atoms in the conduction band. An examination of the polarization effect and uneven electronic charge distribution between [CaO8]6− and [WO4]2− clusters brought about by structural defects in AWO4 (A = Ba, Sr and Ca) was performed. Moreover, advanced investigations have been conducted on the elastic constants and mechanical durability of AWO4 (A = Ba, Sr and Ca). This research extensively calculated the elastic moduli of various matrices utilizing DFT. The critical Pugh’s ratio value was found to be >1.75, it indicated that AWO4 (A = Ba, Sr and Ca) has significant potential as a resilient material.

Controllable Phase Separation Engineering of Iron-Cobalt Alloy Heterojunction for Efficient Water Oxidation.

The tailor-made transition metal alloy-based heterojunctions hold a promising prospect for the electrocatalytic oxygen evolution reaction (OER). Herein, a series of iron-cobalt bimetallic alloy heterojunctions are purposely designed and constructed via a newly developed controllable phase separation engineering strategy. The results show that the phase separation process and alloy component distribution rely on the metal molar ratio (Fe/Co), indicative of the metal content dependent behavior. Theoretical calculations demonstrate that the electronic structure and charge distribution of iron-cobalt bimetallic alloy can be modulated and optimized, thus leading to the formation of an electron-rich interface layer, which likely tunes the d-band center and reduces the adsorption energy barrier toward electrocatalytic intermediates. As a result, the Fe0.25Co0.75/Co heterojunction exhibits superior OER activity with a low overpotential of 185 mV at 10 mA cm-2. Moreover, it can reach industrial-level current densities and excellent durability in high-temperature and high-concentration electrolyte (30 wt % KOH), exhibiting enormous potential for industrial applications.

Insights into the Ligand Effect in β-CD@Fe3O4 Composites to Activate Peroxymonosulfate for Efficient Degradation of Pharmaceutical Contaminants: A Study Employing Density Functional Theory

This study presents a detailed investigation into the use of β-cyclodextrin (β-CD) encapsulated iron oxide nanoparticle (β-CD@Fe3O4) composites, modified with different ligands, to activate peroxymonosulfate (PMS) for the degradation of pharmaceutical contaminants, namely, diclofenac, carbamazepine, and erythromycin. The focus is on understanding the ligand effect, particularly using citric acid (CIT), polyethyleneimine (PEI), and cetyl trimethyl ammonium bromide (CTAB), on the degradation performance of these composites. Employing density functional theory (DFT) calculations, this work examines the electronic structure and charge distributions of β-CD@Fe3O4 composites, providing insights into their interaction with various pollutants. The study reveals that the β-CD@PEI@Fe3O4 composite demonstrates superior degradation efficiency due to optimal electrostatic interactions, regardless of the pollutant’s hydrophobicity. On the other hand, β-CD@CIT@Fe3O4 shows moderate efficiency, and β-CD@CTAB@Fe3O4 exhibits selective efficiency, particularly for hydrophobic compounds. These findings underscore the significant role of surface chemistry in modulating the activation of PMS and the degradation of contaminants, opening avenues for designing tailored β-CD composites for environmental remediation.

An in-depth study of the synthesis, electronic framework, and pharmacological profiling of 1-(anthracen-9-yl)-N-(4-nitrophenyl) methanimine: In vitro and in silico investigations on molecular docking, dynamics simulation, BSA/DNA binding and toxicity studies

The synthesis, electrical structure, and biological characteristics of Schiff bases produced from nitro aniline and 9-anthraldehyde have been thoroughly investigated in this work. Advanced spectroscopic methods, such as FT-IR, NMR, and UV–VIS spectroscopies, were used to carefully characterise the compounds. The synthesis of Schiff bases was conclusively verified by the FT-IR spectrum analysis, as shown by distinctive absorption bands that matched the imine group's stretching vibrations. The compounds' significant bathochromic shift, which is suggestive of their electronic transitions, was discovered by UV–VIS analysis. The reduced band gap that has been observed highlights the molecules' reactivity. Through a variety of wave function studies, the distribution of electronic charge was further clarified, offering insights into the behaviour of the molecules. Through the use of insilico toxicity studies, molecular docking, molecular dynamics simulations, BSA and DNA binding assays, and antimicrobial assays, the biological potential of the synthesised compounds was thoroughly evaluated. This study is unique since it is the first in-depth report on the thorough biological and theoretical analysis of these chemicals.

Time-resolved x-ray spectroscopy of nucleobases and their thionated analogs.

The photoinduced relaxation dynamics of nucleobases and their thionated analogs have been investigated extensively over the past decades motivated by their crucial role in organisms and their application in medical and biochemical research and treatment. Most of these studies focused on the spectroscopy of valence electrons and fragmentation. The advent of ultrashort x-ray laser sources such as free-electron lasers, however, opens new opportunities for studying the ultrafast molecular relaxation dynamics utilizing the site- and element-selectivity of x-rays. In this review, we want to summarize ultrafast experiments on thymine and 2-thiouracil performed at free-electron lasers. We performed time-resolved x-ray absorption spectroscopy at the oxygen K-edge after UV excitation of thymine. In addition, we investigated the excited state dynamics of 2-tUra via x-ray photoelectron spectroscopy at sulfur. For these methods, we show a strong sensitivity to the electronic state or charge distribution, respectively. We also performed time-resolved Auger-Meitner spectroscopy, which shows spectral shifts associated with internuclear distances close to the probed site. We discuss the complementary aspects of time-resolved x-ray spectroscopy techniques compared to optical and UV spectroscopy for the investigation of ultrafast relaxation processes.

Symmetry and reactivity of π-systems in electric and magnetic fields: a perspective from conceptual DFT.

The extension of conceptual density-functional theory (conceptual DFT) to include external electromagnetic fields in chemical systems is utilised to investigate the effects of strong magnetic fields on the electronic charge distribution and its consequences on the reactivity of π-systems. Formaldehyde, H2CO, is considered as a prototypical example and current-density-functional theory (current-DFT) calculations are used to evaluate the electric dipole moment together with two principal local conceptual DFT descriptors, the electron density and the Fukui functions, which provide insight into how H2CO behaves chemically in a magnetic field. In particular, the symmetry properties of these quantities are analysed on the basis of group, representation, and corepresentation theories using a recently developed automatic program for symbolic symmetry analysis, QSYM2. This allows us to leverage the simple symmetry constraints on the macroscopic electric dipole moment components to make profound predictions on the more nuanced symmetry transformation properties of the microscopic frontier molecular orbitals (MOs), electron densities, and Fukui functions. This is especially useful for complex-valued MOs in magnetic fields whose detailed symmetry analyses lead us to define the new concepts of modular and phasal symmetry breaking. Through these concepts, the deep connection between the vanishing constraints on the electric dipole moment components and the symmetry of electron densities and Fukui functions can be formalised, and the inability of the magnetic field in all three principal orientations considered to induce asymmetry with respect to the molecular plane of H2CO can be understood from a molecular perspective. Furthermore, the detailed forms of the Fukui functions reveal a remarkable reversal in the direction of the dipole moment along the CO bond in the presence of a parallel or perpendicular magnetic field, the origin of which can be attributed to the mixing between the frontier MOs due to their subduced symmetries in magnetic fields. The findings in this work are also discussed in the wider context of a long-standing debate on the possibility to create enantioselectivity by external fields.

Machine Learning-Assisted Computational Screening of Adhesive Molecules Derived from Dihydroxyphenyl Alanine.

Marine mussels adhere to virtually any surface via 3,4-dihydroxyphenyl-L-alanines (L-DOPA), an amino acid largely contained in their foot proteins. The biofriendly, water-repellent, and strong adhesion of L-DOPA are unparalleled by any synthetic adhesive. Inspired by this, we computationally designed diverse derivatives of DOPA and studied their potential as adhesives or coating materials. We used first-principles calculations to investigate the adsorption of the DOPA derivatives on graphite. The presence of an electron-withdrawing group, such as nitrogen dioxide, strengthens the adsorption by increasing the π-π interaction between DOPA and graphite. To quantify the distribution of electron charge and to gain insights into the charge distribution at interfaces, we performed Bader charge analysis and examined charge density difference plots. We developed a quantitative structure-property relationship (QSPR) model using an artificial neural network (ANN) to predict the adsorption energy. Using the three-dimensional and quantum mechanical electrostatic potential of a molecule as a descriptor, the present quantum NN model shows promising performance as a predictive QSPR model.

BaTiO3-xNy: Highly Basic Oxide Catalyst Exhibiting Coupling of Electrons at Oxygen Vacancies with Substituted Nitride Ions.

The base strength of oxide catalysts is controlled by the electron charge distribution between cations and anions, with unsaturated oxygen ions that have lone pair electrons typically acting as basic sites. Substitution of oxide ions with anions that have different valences, such as nitride and hydride ions, can often generate basic sites. It is plausible that electrons trapped at oxygen vacancy sites could provide increased electron density and shift the highest occupied molecular orbital energy levels of anions upward in the case that the oxygen vacancies couple with surface-substituted anions. The present work demonstrates that high catalytic basicity can be obtained via site-selective doping of anions at face-sharing Ti2O9 dimer sites with oxygen vacancies in BaTiO3-x. This improved basicity stems from the coupling of substituted nitride ions to electrons at oxygen vacancies. The oxynitride BaTiO3-xNy was found to contain nitride ions that have increased electronic charge density on the basis of such interactions. Enhanced surface basicity following doping with nitride ion was also confirmed by CO2 temperature-programmed desorption and infrared spectroscopy in conjunction with the adsorption of CHCl3. The strong Lewis base sites resulting from the formation of the oxynitride evidently facilitated the catalytic activation of C-H bonds to promote Knoevenagel condensation reactions between aldehydes and active methylene compounds with pKa values of up to 28.9.

Hybrid Functional Study on Electronic and Optical Properties of the Dopants in Anatase TiO2.

TiO2 was known as a golden heterogeneous photocatalyst due to its chemical stability, low cost, nontoxicity, and strong oxidizing power. However, anatase TiO2 predominantly absorbs the photon energy in the ultraviolet region (λ < 387.5 nm); therefore, to increase the utilization of sunlight, the approach of doping of metals and nonmetals into pure TiO2 is implemented. Here we incorporate the dopants of Zr, Si, V, W, Ge, Cr, Sn, Mo, and Pb into the TiO2 lattice and study the optoelectronic properties, including the formation energies and the electron charge distributions, using the Vienna ab initio Simulation Package (VASP) from the hybrid functional of Heyd, Scuseria, and Erhzerhof (HSE06). We observed that V-, Mo-, and Cr-doped systems introduce shallow impurity states within the band gap, and those states influence the shift of the absorbance spectra to visible light by enhancing the photocatalytic efficiency. W-doped anatase TiO2 structure reduces the band gap of the pure anatase TiO2 by 0.7 eV. Notably, this reduction occurs without the introduction of any impurity states between the band edges. Additionally, the absorption edge of the solar spectrum shifts toward lower photon energy from 3.5 to 3.1 eV. From Bader charge analysis, we observed that mainly the charge transfer occurred from the dopants and charge accumulation happened around nearby oxygen atoms. The ferromagnetism was observed in V-, Cr-, Mo-, and W-doped anatase TiO2 structures due to the charge imbalance of the spin-up and spin-down states.

Vibrational study and effect of copper substitution on the electrical properties of the (C2H5NH3)2CdCl4 hybrid compound

In this paper, elaborated samples (C2H5NH3)2CdCl4 and (C2H5NH3)2Cd0.5Cu0.5Cl4 have been studied by X-ray powder diffraction patterns, Raman and impedance spectroscopy. X-ray diffraction indicates that these compounds crystallize at room temperature in the orthorhombic system. The values of lattice parameters and volume were determined. Raman spectroscopy (RS) analysis was used to identify the different modes of vibration between atoms. This technique confirms the presence of the organic and inorganic chain of the hybrid compounds. The morphological analysis was carried out, and the size of the grain was ascertained using the Image J application. The electrical measurements were performed in the 5 Hz – 10 MHz frequency range and 0–6 V bias voltage interval. The capacitance behavior as a function of frequency is explained by the interface states effect. It is noted that the capacitance increases with the introduction of copper in (C2H5NH3)2CdCl4 hybrid compound. The C–V curves show three regions of electronic charge distribution: (a) inversion, (b) depletion and (c) accumulation. The frequency dependence of the conductivity is interpreted in term of Jonscher law. The increase of the conductivity is attributed to the incorporation of copper in (C2H5NH3)2CdCl4 compound.

Density functional theory study of NO adsorption on the transition metal M (M=Cu, Fe and Mn) modified TiO2 surface

To study the effect of different kinds of transition metals and their proportions on NO adsorption on TiO2 surface, the density functional theory (DFT) method was used to calculate the energetic, geometric structure and electronic structure of the adsorption of NO on transition metal M (M = Cu, Fe and Mn)-anatase TiO2 (101) surface. The above transition metals were adsorbed on anatase TiO2 (101) surface in three different adsorption ratios, which are single transition metal adsorption model, mixed 2:2 and 1:3 ratio models. On the basis of the study, 13 models were established to study the effects of transition metals and adsorption ratio on NO oxidation to determine the optimal adsorption model. It has been found from the energetic calculations that mixed adsorption model is more stable for the adsorption of NO. The results of electronic structure and charge distribution analysis showed that a large quantity of active electron clusters are distributed around Mn and Fe atoms, which are attached to a large area of N atoms in NO, indicating that Mn and Fe can provide more electrons for catalytic reaction and facilitate electron exchange between catalyst and NO. Among all the adsorption models, the 3Fe+1Mn–TiO2 and 3Mn+1Fe–TiO2 models are superior, i.e., they can exchange more electrons with NO before the catalytic reaction, which is conducive to the subsequent catalytic reaction.

Computational Study for Insight into LixNiO2 Interlayer Collapse and Pillar Dopant to Counter Oxygen Charge-Transfer at High Depth of Charge (x < 0.25)

As demand for high power and energy capacity has continued to rise, increasing nickel content in Li[Ni1-y-zCoyMnz]O2 (NCM) or Li[Ni1-y-zCoyAlz]O2 (NCA) cathode materials has been the subject of extensive study to improve the specific capacity of Li-ion batteries. Commercialized (Ni composition ~60%) NCM/NCA can deliver specific capacity near 170 mAh/g while LixNiO2 (LNO) has been shown to offer over 200 mAh/g, but coincidently suffers from instability, and anisotropic volume strain due to Ni(III)-O6 Jahn-Teller (JT) distorted shearing and especially lattice collapse during charging. The resulting crack formation in primary particles and pulverization of secondary particles increases surface area exposed to the liquid electrolyte and accelerates phase decomposition due to oxygen evolution and side reactions, with capacity fading increasingly well studied and characterized, including the known chemical instability of Ni—O system yields oxygen redox and evolution at LNO surfaces near 4.2 V. In potential solid-state battery applications, the mechanical nature of large anisotropic strain will incur broken contact with solid electrolyte and shorten lifespan. As the most critical lattice collapse occurs in charging beyond 75% de-lithiation (x < 0.25), mitigation by implementing cutoff voltage near 4.2 V (vs Li anode) has commonly been implemented, consequently restricting practical energy density. Detailed analysis of electronic charge and charge density distribution via first-principles calculations reveals oxygen-nickel charge transfer during charge/discharge is well correlated to oxygen-cation coordination. While charging, each Ni layer shrinks monotonically throughout de-lithiation, from 2.17 Å to 1.9 Å, and the Li interslab thickness first increases, from 2.55 Å to 2.82 Å at 75% de-lithiation, then decreases to 2.48 Å. The former is consistent with the perspective of Ni(III) [3d7: t2g 6 eg 1] oxidation to smaller Ni(IV) [3d6: t2g 6 eg 0], collaborated by respective magnetic moments, a / b lattice constant decrease, and Ni-O bond length changes associated with the loss of JT distortion. The interslab behavior, however, requires recognition of Ni-O bonding character of eg states, where modeling the interslab expansion and collapse in finer detail confirms approximately linear behavior in each regime, notably collapsing even with low but finite Li (e.g. 20-8%) in each interlayer (no empty layers or stacking order transitions). By Bader charge analysis, it is found that Ni exhibits less redox activity directly; rather oxygen charge is more significantly depleted due to charge transfer as eg bonding states are de-occupied by electrons during charge, indicated in projected density of states. Smaller and substantially charge-depleted oxygens appear around 25% Li content and were all identified as oxygens lacking any Li nearest neighbors. Intuitively, as concentrations progress below 25% (> 4.2 V), the number of such oxygen rapidly increases with a corresponding dwindling of higher charge state oxygens local to the few remaining Li. The interslab (Li-layer) thickness decrease follows from these smaller oxygen ins and significantly lessened repulsion across the Li layer in local close-packed, O3 stacking sequence. To mitigate the collapse, high valent cations as dopants at Li-site are investigated in similar detail with this mechanism in mind. Potential cations were chosen on a basis of compatibility with Li-site octahedra, with radii similar to Li+, and less comparable to Ni(II), Ni(III), or Ni(IV). Models of LNO doped as Lix-yMyNiO2 are found to donate charge to all six neighboring oxygen and the respective NiO6 octahedra throughout de-lithiation (decreasing x, 1 > x > y). The charge-compensated oxygens retain stronger local coulomb interaction near the cation dopant and provide a pillaring effect to reduce lattice collapse even to 100% depth of discharge. Select dopants indicate low anisotropy and volumetric strain, e.g. ∆V/V ~ 2% over the range of 0-90% capacity. The presented role of cation dopants reinforces the promise of “zero-strain” LNO cathode material, with simultaneous improvement to thermal and mechanical stability, encouragingly reported by experimental works, and both greater capacity and power by unlocking deeper charging.

Cationic and anionic defect decoration of CoO through Cu dopants and oxygen vacancy for a High‑Performance supercapacitor

CoO has attracted increasing attention as an electrochemical energy storage owing to its excellent redox activity and high theoretical specific capacitance. However, its low inherent electrical conductivity results in sluggish reaction kinetics, and the poor rate capability of CoO limits its widespread applications. Herein, a multiple-defect strategy of engineering oxygen vacancies and Cu-ion dopants into the low-crystalline CoO nanowires (Ov–Cu–CoO) is successfully applied. Because of the advantage of the dual defect synergetic effect, the electronic structure and charge distribution are effectively modulated, thus enhancing the electrical conductivity and enriched redox chemistry. The obtained Ov–Cu–CoO electrode exhibits a high specific capacity of 1388.6 F⋅g−1 at a current density of 1 A⋅g−1, an ultrahigh rate performance (81.2% of the capacitance retained at 20 A⋅g−1) and excellent cycling stability (101.1% after 10,000 cycles). Moreover, an asymmetric supercapacitor device with Ov–Cu–CoO as the positive electrode having a high energy density of 44.1 W⋅h⋅kg−1 at a power density of 800 W⋅kg−1, and can still remain 27.2 W⋅h⋅kg−1 at a power density of 16 kW⋅kg−1. This study demonstrates an effective strategy to enhance electrochemical performance of CoO that can be easy applied to other transition metal oxides.

Ample Lewis Acidic Sites in Mg2B2O5 Facilitate N2 Electroreduction through Bonding-Antibonding Interactions.

Extensive research on the electrochemical nitrogen reduction reaction (NRR) has put forward a sound list of potential catalyst materials with properties inducing N2 adsorption, protonation, and reduction. However, rather than a random selection of catalysts, it is essential to understand the vitals in terms of orbital orientation and charge distribution that actually manipulate the rate-determining steps of NRR. Realizing these factors, herein we have explored a main group earth-abundant Mg-based electrocatalyst Mg2B2O5 for NRR due to the abundance of Lewis acid sites in the catalyst favoring the bonding-antibonding interactions with the N2 molecules. Positron annihilation studies indicate that the electronic charge distribution within the catalyst has shallow surface oxygen vacancies. These features in the catalyst enabled a sound Faradaic efficiency of 46.4% at -0.1 V vs reversible hydrogen electrode for the selective NH3 production in neutral electrolyte. In situ Fourier transform infrared suggests a maximum N-N bond polarization at -0.1 V and detected H-N-H and -NH2 intermediates during the course of the NRR on the catalyst surface. In a broader picture, the biocompatibility of Mg2+ diversifies the utility of this catalyst material in N2/biofuel cell applications that would certainly offer a green alternative toward our goal of a sustainable society.

A combined theoretical and experimental study of the D-2-aminobutyric acid L-norvaline single crystal for efficient third-order nonlinear optical (NLO) applications

Here we report, the formation of an optically active single crystal of D-2-aminobutyric acid L-Norvaline (ABANV) by the slow evaporation technique by co-crystallization of amino acids D-2-aminobutyric acid (ABA) and L-Norvaline together in water. An X-ray diffraction technique has been used to determine the dimensions of the single crystal unit cells. The functional group of ABANV crystal was studied using FTIR spectroscopy in order to determine its chemical structure. The FT NMR spectrum was conducted to analyze the carbon and hydrogen environments of the grown crystal. In optical absorption studies, the crystal was shown to be transparent in the visible region with a lower cut off wavelength of 236 nm, which led to an optical band gap energy Eg of 5.25 eV. In addition, using TG/DSC techniques, we have investigated the thermal stability of the grown ABANV single crystal as well as their accurate melting point. A HOMO and LUMO analysis were performed to determine the electronic charge distribution and reactivity of the molecules within the crystal. First-order molecular hyperpolarizality (β) properties of the grown crystal have been determined using the B3LYP method. The scatter graph provides an explanation of the chemical bonding of ELF and LOL, as well as the inter and intra fragment interactions.

The Effect of the Interface Layer on the Electronic Parameters of the Light Emitting Electrochemical Cell (LEC) Device Based on Iridium (III) Complex that Calculated by Different Methods

We report a calculation of the electronic parameters and some optical measurement results of a light-emitting electrochemical cell (LEC), one of the most basic forms of electroluminescent films by modifying 4-(4-methoxy-N-naphthalen-1-ylanilino) benzoic acid (MA) as hole injection layer doped with an emissive layer that is ionic transition metal complex (Ir[dF(CF3)ppy]2(dtbpy))PF6-(Ir-iTMC). The electronic parameters of LEC device were computed using three different methods; Cheung and Cheung’s, Conventional Schottky and Norde, to evaluate the ideality factor (n), the barrier height () and the series resistance (Rs) of the LEC device. The formation on indium tin oxide (ITO) substrate was analyzed by Atomic Force Microscopy (AFM). The HOMO-LUMO energy level and electronic charge distribution of the MA molecule were computed theoretically using Chemissian software. The MA’s HOMO-LUMO energy level is determined to be EHOMO = −5.27 eV and ELUMO = −1.40 eV. The ITO surface has been modified with the Self-Assembled Monolayers (SAM) technique as an interlayer to improve the surface working function by simplifying hole injection from the ITO anode to the Hole Transport Layer (HTL) in the LEC. The Ir- iTMC complexes containing Π-conjugated bridging ligand shown better external quantum efficiency (EQE), reaching to 1.49%. The max luminance values of the bare-LEC and LEC-MA are measured as 145 cd m−2 and 1240 cd m−2, respectively.

Atomic and electronic structures of an Ag-containing 4A zeolite

Atomic structure of an Ag-containing 4A zeolite with the Ag/Al atomic ratio of about 10% was investigated by a pair distribution function (pdf) analysis. Valence- and conduction-band O 2p partial electronic structures of this insulating material were respectively measured by soft X-ray emission and absorption spectroscopies using an O 1s-2p resonance technique. Moreover, a density functional theory (DFT) hybridized by 25% of Hartree–Fock exchange was applied to determine the atomic structures and electronic states. Although the box size of the DFT calculation was small due to the limited computational power, the present DFT results excellently reproduce the pdf data as well as O 2p partial electron density of states (DOS). The electronic charge distributions in this zeolite with an antibacterial function obtained by the present DFT calculation revealed half-filled charges on the Ag atoms, which may act as a formation of deactivating the bacteria.

Computational Insights and Virtual Screening of Repurposed FDA-Approved Drug Against SARS-CoV-2 Protease

In recent times, the emergence of novel Coronavirus and the successive mutations in the viral genome has posed a major threat to public health with strikingly high mortality and morbidity rates across the globe. To address the health concern, the current scenario demands the need for effective therapeutics and at present, the anti-viral drug Remdesivir has been used worldwide to combat the disease. Therefore, in this present study, we have adopted structure-based virtual screening approach to assess the inhibitory potential of the five structural analogues of Remdesivir (Rm) against SARS-CoV-2 main protease (Mpro) using Autodock molecular docking tool. Density functional theory (DFT) calculations have been carried out to gain deep insights into the electronic structure of these analogues. The low HOMO–LUMO gap implies that Rm3 is chemically active and MEP analysis shed light on the possible regions of electronic charge distribution. From the docking results, the analogue compound Rm5 has been identified to exhibit effective inhibitory effect with higher binding affinity (−7.8 kcal mol−1). Most of the docked compounds, however, were found to exhibit good drug-likeness properties and hence could serve as potential candidates against SARS-CoV-2 Corona virus.

Third-order nonlinear response of a novel organic acetohydrazide derivative: Experimental and theoretical approach

A novel nonlinear optical (NLO) organic material of N'-[(E)-(5-bromofuran-2-yl)methylidene]-2-(6-chloropyridin-3-yl)acetohydrazide (BCA) was synthesized by reflux method. The synthesized material was characterized using various analytical techniques, including spectroscopic methods (NMR, FTIR, PXRD). The UV–Vis absorption spectrum of BCA was recorded in different solvents. A strong absorption peak was observed in the 280–350 nm range, indicating its potential for UV-based optoelectronic applications. BCA shows good NLO responses (αCT, βCT, γCTvalues) with different solvents. The dielectric measurements were performed using impedance spectroscopy with varying temperatures as a function of frequency. Thermal stability of the material was evaluated using thermogravimetric analysis, indicating high thermal stability up to 153.28°C. The FMO, MEP, and NBO analyses were implemented using density functional theory (DFT) calculations to investigate the BCA molecule's electronic structure and charge distribution. The topology studies were carried out using the QTAIM and NCI to understand the structure's chemical bonding and intermolecular interactions and the structure's chemical bonding and intermolecular interactions. NLO properties of the BCA material were investigated using the Z-scan technique with a continuous wave (CW) laser, revealing a strong third-order nonlinear susceptibility (χ(3)) value of 2.44 × 10−6 e.s.u. and potential optical limiting behavior (OL threshold = 3.437 × 103 Wcm−2). The TD-HF method performed the calculated molecular static and dynamic of NLO parameters with frequency. The computed γ value of 6.2 × 10−36 e.s.u. was found to be consistent with the experimental value. The results of this study recommend that the synthesized hydrazide derivative material has potential NLO applications.

First-principles calculations investigation on different coverage of H2O adsorption on the Mg-montmorillonite (0 1 0) edge surface

Clay minerals are often cause of deformation in soft rock tunnel engineering, leading to safety problems. The deformation mechanism is closely related to the interaction between clay minerals and water molecules. Mg-montmorillonite (Mg-MMT) with good adsorbability is one of the most abundant components in clay minerals. In the present paper, the density functional theory was employed to clarify the adsorption mechanism of H2O on the Mg-MMT (010) surface at the molecular level. The adsorption structures and energies of H2O molecules on the Mg-MMT (010) surface were systematically studied for a wide coverage from 0 to 1.0 monolayer (ML). The results showed that the interlayer-bridge site was the most favorable for water molecules adsorption, and followed by the hollow, bridge, and top adsorption sites. When the coverage was 0.5 ML, the highest adsorption energy for above adsorption sites was 0.71, 0.62, 0.61, and 0.44 eV, respectively. The adsorption energy increased with increasing coverage for water molecules in range of 0 < Θ ≤ 0.5 ML, while decreased with the coverage range of 0.5 < Θ ≤ 1.0 ML. The above results implied that water molecules could be easily adsorbed on the Mg-MMT (010) surface. Besides, other properties of the H2O/Mg-MMT (010) surface system, including the atomic structures, bonding analyses, density of electronic states and charge distribution were also studied in detail for different coverages.