Electron Density Properties Research Articles

Computational analysis of 1T-MoS2: Probing the interplay of layer-dependent electronic structure, quantum capacitance, charge density and mechanical properties

To meet the high energy demand of society, a conversion to renewable energy sources has become essential and energy should be appropriately stored for future use. This has led to the development of energy-storing devices such as supercapacitors (SCs). To enhance capacitive behavior, the concept of quantum capacitance (CQ) is unveiled, which results from the confinement of electrons in their energy states. In this work, 1T phase of MoS2 is studied as it has received a lot of attention because of its wide applications in the energy storage devices and electronics. Here, the electronic structure, CQ and surface charge density (σ) of one, two and three-layered structures of 1T phase is studied using Density Functional Theory. No bandgap is obtained in the Density of States (DOS) and the bands plot of 1T structure indicates their metallic character and the DOS is continuous in all three layers. The CQ of three-layered structure dominates over the other two layers throughout the potential window. The larger CQ and σ values are obtained as 1718.06 μF cm−2 and -1299.50 μC cm−2 for three-layered structure at −0.27 V and −1 V respectively. For analyzing the mechanical strength, Young's modulus is evaluated for optimized structure by applying uni-axial strain. The value is obtained as 177.37 GPa, which is a measure of elastic deformation behavior. The results suggest that the capacitive performance of 1T MoS2 for SC applications is better and it can function as flexible cathode material for asymmetric SC applications.

Fine-tuning the photophysical properties of Imidazo[1,2-a]pyridine-based dyes by the change in substituent and solvent media: DFT and TD-DFT studies

In the present work, photophysical properties of the nine excited-state intramolecular proton transfer (ESIPT) active 2-(2 -hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP)-based dyes A1-A9 (X= H, Me, F, Cl, OMe, OH, CN, NO2 and CF3) were investigated at PBE0/6-31++G(d,p) and M06-2X/6-31++G(d,p) levels of theory in the gas phase and solvent media. The structural parameters, relative energies, vibrational spectra, photophysical properties, potential energy curves, natural bond orbital (NBO) charges, hole and electron isosurfaces, electron density properties and reduced density gradient (RDG) spikes were computed. The H-bonding is strengthened at the S1 state by comparing infrared vibrational spectra, the relevant bond length and bond angle, electron density properties and RDG analysis. The results revealed that ESIPT in the A1-A7 and A9 in the gas phase is a barrier-less process, while there is an energy barrier for the A8 (X=NO2). In polar solvents, it is predicted that the ESIPT process only in A5 and A6 is a barrier-less process. The A2, A4 and A5 exhibited the greatest redshift in the keto fluorescence emission in tetrahydrofuran solvents. The significant Stokes shift observed in the S1-K emission of certain dyes makes these molecules highly appealing for various applications such as chemosensors, fluorescent probes, laser dyes and optoelectronic devices.

Synergistic Strain Suppressing and Interface Engineering in Na4MnV(PO4)3/C for Wide-Temperature and Long-Calendar-Life Sodium-Ion Storage.

A Na4MnV(PO4)3 (NMVP) cathode is regarded as a promising cathode candidate for sodium-ion batteries (SIBs). However, issues such as low electronic conductivity and partial cation dissolution contribute to high polarization and structure distortion. Herein, we engineered the local electron density and reaction kinetic properties of NMVP cathodes with varying oxygen vacancies by introducing varying amounts of Zr doping and carbon coating. The optimized sample exhibited a high-rate capacity of 71.8 mAh g-1 at 30 C (83.1% capacity retention after 1000 cycles) and excellent performance over a wide temperature range (84.1 mAh g-1 at 60 °C and 61.4 mAh g-1 at -30 °C). In situ X-ray diffraction technology confirmed a redox solid solution and a two-phase reaction mechanism, revealing minor changes in cell volume and slight strain variations after Zr doping, effectively suppressing the structural distortion. Theoretical calculations illustrated that Zr doping largely shrinks the band gap of NMVP, enriches local electron density, and slightly alters the local element distribution and bond lengths. Moreover, full-cells have shown high energy density (259.9 Wh kg-1) and outstanding cycling stability (200 cycles). The work provides fresh insights into the synergistic effect of strain suppressing and interface engineering in promoting the development of wide temperature range and long-calendar-life SIBs.

Computational analysis of substituent effects on proton affinity and gas-phase basicity of TEMPO derivatives and their hydrogen bonding interactions with water molecules

The study investigates the molecular structure of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives in the gas phase using B3LYP and M06-2X functional methods. Intermolecular interactions are analyzed using natural bond orbital (NBO) and atoms in molecules (AIM) techniques. NO2-substituted TEMPO displays high reactivity, less stability, and softer properties. The study reveals that the stability of TEMPO derivatives is mainly influenced by LP(e) → σ∗ electronic delocalization effects, with the highest stabilization observed on the oxygen atom of the nitroxide moiety. This work also considers electron density, atomic charges, and energetic and thermodynamic properties of the studied NO radicals, and their relative stability. The proton affinity and gas-phase basicity of the studied compounds were computed at T = 298 K for O-protonation and N-protonation, respectively. The studied DFT method calculations show that O-protonation is more stable than N-protonation, with an energy difference of 16.64–20.77 kcal/mol (22.80–25.68 kcal/mol) at the B3LYP (M06-2X) method. The AIM analysis reveals that the N–O…H interaction in H2O complexes has the most favorable hydrogen bond energy computed at bond critical points (3, − 1), and the planar configurations of TEMPO derivatives exhibit the highest EHB values. This indicates stronger hydrogen bonding interactions between the N–O group and water molecules.

Exploring the photophysical properties of flavone-based dyes as an anti-angiogenic agent and with fluorescence emission in the near-infrared (NIR) region: a TD-DFT study

In this work, photophysical properties of the flavone-based dyes APG, BCN, CYS, LUT, and OX-A were investigated using TD-DFT calculations at PBE0/6-311++G (d,p) level in the gas phase and solvent media. The structural parameters, absorption and emission spectra, potential energy curves, natural charges, electron density properties, reduced density gradient, and protein–ligand docking properties were calculated. In the S1 state, the normal form of all dyes was directly converted to its tautomeric T form by no energy barrier. The results demonstrated that O1–H2···O6 H-bonding at S0 state is stronger than O1···H2–O6 one at S1 state. Upon photoexcitation to the S1 state, the flavones exhibit keto fluorescence emission in the near-infrared (NIR) wavelengths of 848.0 nm for APG to 1143.1 nm for OX-A, making the application of these molecules more attractive in the medical and physiological diagnostics. In addition, the anti-aging properties of the flavonoids were studied by docking process on the two aging targets brain-derived neurotrophic factor (BDNF) and nerve growth factors (NGF). Our study can provide insights into the design of a flavone-based ESIPT fluorescent probe and its anti-aging properties which might inspire future applications in the field of chemical sensing, imaging and drug design.

The electronic structure, electronic charge density, optical and thermoelectric properties of Mo and Rh based triple perovskite semiconductors Ba3CaNb2O9 for low-cost energy technologies

The electronic structure, electronic charge density, optical and thermoelectric properties of Mo and Rh based triple perovskite semiconductors Ba3CaNb2O9 for low-cost energy technologies

Stability trend analysis of light lanthanide complexes with a fluorophenyl-dipicolinamide: A quantum chemical study

Extracting lanthanides (Ln) from actinides (An) is a crucial step in reprocessing spent nuclear fuel, and the interaction between ligands and Ln inevitably deserves careful study. In this study, we employ density functional theory (DFT) calculations to analyze the stability trend of trivalent light lanthanides (Ln (III), from La(III) to Eu(III)) complexes with N,N'‑diethyl-N,N'-di(para)fluorophenyl-2,6-dipicolinamide (FDPA), which has emerged as a promising ligand in Ln-An separation. The bond length, nature of bonding and electronic energy density properties of Ln-N and Ln-O bonds have been investigated. The quantum theory of atoms in molecules calculation shows that Ln(III)-FDPA complexes are stable, via closed-shell interactions. The Gibbs free energy changes (∆G) of La(III), Pr(III), Pm(III), Sm(III), and Eu(III) complexes with FDPA are approximately -0.07 Kcal/mol. In contrast, the ∆G values of Ce(III) and Nd(III) complexes with FDPA are 1.534 and 0.781 Kcal/mol, respectively. These findings indicate that La(III), Pr(III), Pm(III), Sm(III), and Eu(III) can be excellently extracted by FDPA from acidic solvents, whereas Ce(III) and Nd(III) do not. Our study contributes to a better understanding of the mechanism of lanthanide complexes and provides guidance for the design of ligands that can effectively discriminate lanthanides in nuclear waste reprocessing.

Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs?

In the manuscript, we check properties of electron densities n e traced by flux ratio R sii of [S ii]λ6716 Å to [S ii]λ6731 Å in narrow emission line regions (NLRs) between Type-1 active galactic nucleus (AGN) and Type-2 AGN in SDSS Data Release 12 (DR12). Under the framework of unified model considering kiloparsec-scale structures, similar n e in NLRs should be expected between Type-1 AGN and Type-2 AGN. Based on reliable measurements of the [S ii] doublet with measured parameters at least 5 times larger than corresponding uncertainties, there are 6039 Type-1 AGN and 8725 Type-2 AGN (excluding the Type-2 LINERs and the composite galaxies) collected from SDSS DR12. Then, lower R sii (higher n e ) in NLRs can be well confirmed in Type-1 AGN than in Type-2 AGN, with the confidence level higher than 5σ, even after considering the necessary effects including effects of electron temperatures traced by [O iii]λ4364,4959,5007 Å on estimating n e in NLRs. Two probable methods are proposed to explain the higher n e in NLRs in Type-1 AGN. First, the higher n e in NLRs of Type-1 AGN could indicate longer time durations of AGN activities in Type-1 AGN than in Type-2 AGN, if AGN activities triggering galactic-scale outflows leading to more electrons injecting into NLRs were accepted to explain the higher n e in NLRs of Type-2 AGN than H ii galaxies. Second, the lower n e in NLRs of Type-2 AGN could be explained by stronger star-forming contributions in Type-2 AGN, considering lower n e in H ii regions. The results provide interesting challenges to the commonly and widely accepted unified model of AGN.

Decoding Chemical Bonds: Assessment of the Basis Set Effect on Overlap Electron Density Descriptors and Topological Properties in Comparison to QTAIM.

Quantum chemical bonding descriptors based on the total and overlap density can provide valuable information about chemical interactions in different systems. However, these descriptors can be sensitive to the basis set used. To address this, different numerical treatments of electron density have been proposed to reduce the basis set dependency. In this work, we introduce overlap properties (OPs) obtained through numerical treatment of the electron density and present the topology of overlap density (TOP) for the first time. We compare the basis set dependency of numerical OP and TOP descriptors with their quantum theory of atoms in molecules (QTAIM) counterparts, considering the total electron density. Three single (C-C, C-O, and C-F) bonds in ethane, methanol, and fluoromethane and two double (C═C and C═O) bonds in ethene and formaldehyde were analyzed. Diatomic molecules Li-X with X = F, Cl, and Br were also analyzed. Eight parameters, including QTAIM descriptors and OP/TOP descriptors, are used to assess the basis dependency at the ωB97X-D level of theory using 28 basis sets from three classes: Pople, Ahlrichs, and Dunning. The study revealed that the topological overlap electron density properties exhibit comparatively lesser dependence on the basis set compared to their total electron density counterparts. Remarkably, these properties retain their chemical significance even with reduced basis set dependency. Similarly, numerical OP descriptors show less basis set dependency than their QTAIM counterparts. The excess of polarization functions increases charge concentration in the interatomic region and influences both QTAIM and OP descriptors. The basis sets Def2TZVP, 6-31++G(d,p), 6-311++G(d,p), cc-pVDZ, cc-pVTZ, and cc-pVQZ demonstrate reduced variability for the tested bond classes in this study, with particular emphasis on the triple-ζ quality Ahlrichs' basis set. We recommend against using basis sets with numerous polarization functions, such as augmented Dunning's and Ahlrichs' quadruple-ζ.

Investigations on 355 nm picosecond laser machining of carbon fiber reinforced polymer composites

Carbon fiber reinforced polymer (CFRP) composites have emerged as excellent performance structural materials with a wide range of applications in the aerospace industry. Ultrafast laser is a promising and versatile tool for manufacturing these composites due to its advantages of high peak intensity and ultrashort pulse duration. Herein, a theoretical model based on the Fokker–Planck law and the two-temperature equation, i.e. the ultrafast responses of a two-dimensional heterogeneous material assembly of resin matrix padded with carbon fiber reinforced phase irradiation by 355 nm picosecond laser is established. The evolution of laser-excited free electron density is analyzed, and the relationship between the optical properties of substrate and electron density is revealed. The spatial and temporal distribution of electron and lattice temperatures are thus characterized. The ablation thresholds of resin and carbon fiber are determined, the accuracy of which are verified by experiments. On this basis, orthogonal experiments are conducted to analyze the influence law of process parameters on the ablation depth and heat affected zone (HAZ) width. Optimized parameter groups are discovered to realize the high-quality machining of CFRP composite with considerable depth-to-width ratio and limited HAZ width. This work offers new insight into the fundamental regimes and high-quality machining for picosecond laser manufacturing of CFRP composites.

Effect of Introducing Defects and Doping on Different Properties of Monolayer MoS2

Herein, the comprehensive study of different properties of undoped MoS2, MoS2 lattice with sulfur (S) and, molybdenum (Mo) vacancy, and MoS2 with substitutional doping of niobium (Nb), vanadium (V), and zinc (Zn) atoms is done. The density functional theory (DFT) is used and the electronic properties like density of states, band structure, electron density, and optical properties like dielectric function, optical conductivity, and refractive index are studied. It is observed that undoped MoS2 monolayer shows direct bandgap semiconductor characteristics with a bandgap of around 1.79 eV. P‐type characteristics are observed for Nb‐, V‐, and Zn‐doped MoS2 lattices. The real part and imaginary parts of all optical parameters along x and z directions for different MoS2 supercells are found to be anisotropic in nature up to a photon energy of almost 11 eV and thereafter they show nearly isotropic nature. Finally, it is found that the obtained properties of MoS2 monolayer as per literature are suitable for next‐generation MOSFET application.

Effect of gas flow on the nanoparticles transport in dusty acetylene plasmas

This article presents simulation results on the effects of neutral gas flow for nanoparticle transport in atmospheric-pressure, radio-frequency, capacitively-coupled, and acetylene discharge. The acetylene gas is set to flow into the chamber from the upper showerhead electrode. The internal energy of the gas medium therein is transferred into kinetic energy so the gas advection can be triggered. This is represented by the pressure volume work term of the gas energy converse equation. The gas advection leads to the gas temperature sink at the gas inlet, hence a large gas temperature gradient is formed. The thermophoresis relies on the gas temperature gradient, and causes the profile of nanoparticle density to vary from a double-peak structure to a single-peak one. The gas advection influences the properties of electron density and temperature as well and causes the drift-ambipolar mode profile of electron density asymmetric. In the bulk region, i.e. away from the inlet, the gas advection is more like one isovolumetric compression, which slightly increases the temperature of the gas medium at consuming its kinetic energy.

Experimental and DFT TB-mBJ calculations studies of structural, morphological, electronic, optical and electrical properties of copper oxide thin films

The present work reviews a study of copper oxide (CuO) thin film properties elaborated via two distinct techniques: spin-coating and sprays pyrolysis. The primary objective of the work is to investigate the experimental results and theoretical finding by DFT TB-mBJ calculations of pure CuO films. First of all, the structural properties were studied by X-ray diffraction; Where the CuO films show polycrystalline and monoclinic structures without any other phases. Furthermore, Field emission scanning electron microscopy (FESEM) investigates the effects of elaboration methods on the morphology and surface composition and also, the film thickness was about 234,1 nm for sprayed film and 449 nm for spin-coated films. Moreover, the Optical analysis exhibits a higher absorbance for sprayed films than the spin-coated ones where the band gap energy was found 1.25 eV for using spin-coated and 1.35 eV for sprayed thin films respectively. Furthermore, the electrical conductivity of the spin coated films is higher than the sprayed ones. The band structure, density of states (DOS), electronic density and optical properties of pure CuO were estimated using the LDA approximation in conjunction with the TB-mBJ approximation in order to investigate its characteristics. These results indicate that the CuO films are suitable to be used as an absorber of thin-film solar cells.

NLO ACTIVITY AND COMPUTATIONAL DISCUSSION OF HALOGEN-SUBSTITUTED CHALCONE DERIVATIVES

The four halogen-substituted chalcones 1–4 have been synthesized and analyzed to FT-Infrared, UV-Visible, GC-MS spectrometer, and 1D NMR (1H and 13C) spectroscopy techniques. Computational calculations were carried out for geometrical optimization of structure regards bond length, bond angle, and torsional angle estimated. The molecular properties of donor-acceptor electron delocalization (NBO), Electron density, and bond critical point are carryover in (AIM), the polar site of molecules is determined by (MEP), HOMO-LUMO, and the dipole moment was calculated by GAUSSUION-09 Package. The polarizability and first-order hyperpolarizability calculations derived from non-linear optical (NLO) properties for the synthesized compounds (1-4). The disc diffusion method was used to investigate the microbial activity of antibacterial and antifungal activity.

Investigation of C–F···F–C Interactions Using Experimental and Theoretical Charge Density Analyses

Among the halogens, fluorine plays a crucial role in governing the potency of drugs and pharmaceuticals. In this study, experimental and theoretical charge density analyses have been performed on N-(2,5-difluorophenyl)-3,5-difluoro-N-(3-methoxyphenethyl)benzamide to study the nature of weak intermolecular interactions, especially the F···F interactions, mediated by organic fluorine. The kind of C–F···F–C interactions analyzed in this study are Type I and quasi Type I/Type II. For this, the quantitative and qualitative analyses of electron densities have been performed based on the multipole modeling of high-resolution experimental X-ray diffraction data and theoretical structure factors generated from periodic calculations. The interactions have been analyzed based on the topological properties of electron densities using quantum theory of atoms in molecules (QTAIM). Thus, the nature of organic fluorine has been investigated by studying deformation of electron densities, Laplacian, and topological parameters.

Substituent effect on the photoinduced geometrical changes of Cu[formula omitted]Phen[formula omitted] complexes

This paper analyzes the substituent effect (SE) on the photo-physical process of bis-1,10-phenanthroline copper(I) complexes to provide information that may eventually be useful in designing molecular machines based on this metal. This metal complex’s ground and excited states were calculated, including the vertical, adiabatic, and intersystem crossing points (ISCP). Ab Initio Molecular Dynamics was used to find the time when the ISCP appears. The integrated properties of electron density allowed to detection of SE on the metal-ligand electron transfer and the dihedral angle between the ligands. The properties of the atomic graph permitted the analysis of SE on the equatorial coordination sites.

A comparative study on the physicochemical properties of the nanostructured triazolium based ionic liquids composed of [5F-PhMTZ]+ cation and various anions with their non-fluorinated cation analogues

Newly designed task specific ILs using structural modification of the current non-fluorinated ILs were introduced. Here we chose 1-perfluorophenyl-4-methyl-1,3,4 triazolium [5F-PhMTZ]+ cation and various anions [Y1-10] (Y = Cl-, NO3–, CF3CO2-, BF4-, N(CN)2-, ClO4-, C(CN)3-, PF6-, Tf2N--cis and Tf2N--trans) to investigate the effect of adding fluorine atom on the structure of cationic part and then on the whole of the IL characteristics. All of the obtained results were compared with those previously reported to the same non fluorinated ILs to make deep explanation of fluorination effects on the whole characteristics of the selected ILs. All designed ion pairs, topological properties, interaction energies between constructing parts, Electrostatic potential maps, Volumetric and electron density properties, Frontier molecular orbitals, Electrochemical windows, Natural bonding orbitals analysis, the Density of states were discussed.

Bond Bundle Analysis of Ketosteroid Isomerase.

Bond bundle analysis is used to investigate enzymatic catalysis in the ketosteroid isomerase (KSI) active site. We identify the unique bonding regions in five KSI systems, including those exposed to applied oriented electric fields and those with amino acid mutations, and calculate the precise redistribution of electron density and other regional properties that accompanies either enhancement or inhibition of KSI catalytic activity. We find that catalytic enhancement results from promoting both inter- and intra-molecular electron density redistribution, between bond bundles and bond wedges within the KSI-docked substrate molecule, in the forward direction of the catalyzed reaction. Though the redistribution applies to both types of perturbed systems and is thus suggestive of a general catalytic role, we observe that bond properties (e.g., volume vs energy vs electron count) can respond independently and disproportionately depending on the type of perturbation. We conclude that the resulting catalytic enhancement/inhibition proceeds via different mechanisms, where some bond properties are utilized more by one type of perturbation than the other. Additionally, we find that the correlations between bond wedge properties and catalyzed reaction barrier energies are additive to predict those of bond bundles and atomic basins, providing a rigorous grounding for connecting changes in local charge density to resulting shifts in reaction barrier energy.

Relationship between structure and properties of microwave dielectric ceramic Li(1+x)2MgTi3O8 based on Li non-stoichiometry

Li(1+x)2MgTi3O8 (0.0 ≤ x ≤ 0.10) ceramics with Li non-stoichiometric ratios were prepared by the solid-state reaction method to inhibit the volatilization of Li. The effects of the Li non-stoichiometric ratios on the sintering behavior, crystal structure, microscopic morphology, Raman vibrations, electron density, and dielectric properties of Li(1+x)2MgTi3O8 ceramics were systematically investigated. The Li(1+0.06)2MgTi3O8 ceramics demonstrate the best dielectric properties with εr = 26.33, Q × f = 69 435 GHz (@6.87 GHz, 54% improvement), τf = 2.95 × 10−6 °C−1. For the non-intrinsic factors, the high relative density (97.15%) and larger grain size (16.78 μm) allow the dielectric properties to be improved. As for the intrinsic factors, a reasonable excess of Li improves the bond ionicity of the Mg—O bond, the lattice energy of the Ti—O bond, and the electron cloud density, thus optimizing the dielectric properties. Raman spectroscopy leads to the same result from the point of view of lattice vibrations. At the same time, the distortion of the polyhedra is also improved, so that τf also approaches 0. The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.

Electronegativity effect of (Z[tbnd] S, O, F and Cl) doping on the electrical, electron density and optoelectronic properties of half-Heusler LiMgP: DFT overview

In this paper, the effect of (Z S, O, F and Cl)- dopant has been exanimated on the electronic structure and optoelectronic properties of LiMgP alloy, where the Z amount is 6.25%. Hence, the considered systems are Li16Mg16P15S, Li16Mg16P15O, Li16Mg16P15F and Li16Mg16P15Cl. The LiMgP alloy has an XYZ arrangement which is crystallized in the (N° 216) space group. The present investigation is carried out within the Wien2K package combined with the TB-mBJ approach. Within the study, the Burstein–Moss shift is observed when (Z S, O, F and Cl) where the n-type occurred and the Fermi level lies inside the conduction band (CB). This conduct is significant because it allows obtaining various optical characteristics for the same material. The calculated apparent band gap follows the trend: (Eg+ΔE)Li16Mg16P15Cl>(Eg+ΔE)Li16Mg16P15F and (Eg+ΔE)Li16Mg16P15S>(Eg+ΔE)Li16Mg16P15O. This suggests that the halogen family (Cl and F) has much more effect on LiMgP than the chalcogen family (O and S). Based on the dielectric function, doping leads to a strong move of the absorption edge to low energies, in which four sharp peaks appear at 0.3, 0.6, 0.9 and 1.1 eV due to S, O, Cl and F elements, respectively.