Charge Distribution Research Articles

Design, preparation and properties of biomedical Ti-Nb quaternary alloys with high strength and low modulus: insights from first-principles calculations

In this paper, we designed and developed biomedical β-type Ti-Nb quaternary alloy materials with high strength and low modulus. Building upon the d-electron alloy design method and the valence electron concentration e/a method, we use a Python program and thermodynamic theoretical parameters to determine a Ti-Nb quaternary alloy with the characteristics of a single-phase solid solution. Subsequently, we engage in theoretical and experimental investigations on the low modulus alloys identified through first-principles calculations. The results show that both Ti7Nb6Zr1Al2 and Ti11Nb2Ta2Al1 maintain a single β phase before and after cold rolling, which is related to the strong electronic density of states of s and p orbitals at low energy levels in the crystal structure of the two alloys. Ti11Nb2Ta2Al1 has a strong charge distribution on the (001) crystal plane, which causes a large amount of internal stress under large deformation conditions to promote grain crushing and weaken the intensity of the (001)[1-10] texture in the ODF diagram of 2 = 45°. The cold-rolled Ti11Nb2Ta2Al1 exhibits better corrosion resistance and biocompatibility than the cold-rolled Ti7Nb6Zr1Al2, and the good biocompatibility is related to the strong covalent bond between Al and Ta that inhibits the diffusion of Al ions. 90% cold-rolled Ti11Nb2Ta2Al1 stands out as an exceptionally promising orthopedic implant material due to its high elastic allowable strain (ReH/E), good corrosion resistance and biocompatibility.

Modeling and Analysis of IGBT Based on Two-Dimensional Charge Distribution

Modeling and Analysis of IGBT Based on Two-Dimensional Charge Distribution

Comparative theoretical analysis on the adsorption of cationic and anionic on metal iodides in water

This study focused on the comparative analysis of the adsorption of cationic safranine O (SF+) and anionic acid blue 25 (AB−) on (1 1 0) surface of magnesium, manganese, zinc, and nickel metal iodides using DFT and molecular dynamics (MD) simulation. The nature of the interactions has been thoroughly investigated by the HOMO/LUMO energy gap, global reactivity descriptors, Mulliken charge distribution, molecular electrostatic potential (MEP) map, adsorption energy, and natural bond orbital (NBO) analysis. The reactivity of the two dyes was compared based on the LUMO and HOMO energy levels. It was found that SF+ with a LUMO value of −0.991 eV and lower energy gap of 1.184 eV exhibits an electrophilic characteristic and high ability to be strongly adsorbed on the MI2. However, AB− exhibits a higher energy gap of 5.854 eV, indicating its lower reactivity compared to SF+. Mulliken charge distribution of the dyes and their MEP map also showed strongly negative and strongly positive sites. Subsequently, the stabilizing interactions of hyper-conjugation and charge delocalization have been evaluated. In addition, the MD simulation was employed to elucidate the mechanism of the dye’s adsorption on the adsorbent surfaces. The results suggest that the dyes are adsorbed on the four metal iodides in a close parallel position with less adsorption energy for SF+ compared to AB−. Finally, it was found that the Van der Waals forces are predominant in the adsorption process suggesting a physisorption mechanism in accordance with RDF analysis.

Measurement of fission product yields in the quasi-mono-energetic neutron-induced fission of 238U

The cumulative yield of the fission products within the mass range of 83–117 and 123–153 have been measured in the 6.61and 10.92 MeV quasi-mono-energetic neutron-induced fission of 238U by using an off-line γ-ray spectrometric technique. The neutron beams were obtained from the 7Li(p,n) reactions with the proton energies of 11 and 18.8 MeV. The mass chain yields were obtained from the cumulative yields by using charge distribution correction. The peak-to-valley (P/V) ratio, the average value of light mass (⟨AL⟩), heavy mass (⟨AH⟩) and the average number of neutrons (<ν>) were obtained from the mass yield data. The data in the 238U(n, f) reaction from the present work and literature at various energies were compared with the similar data in the 238U(γ, f) reaction and following observations were obtained. (i) In both the reactions, the mass yield distributions are double humped. (ii) The yield of fission products for A = 133–134, A = 138–139, and A = 143–144 and their complementary products are higher than those of other fission products due to the nuclear structure effect. (iii) The yield of symmetric product increases and thus the peak-to-valley (P/V) ratio decreases with excitation energy. (iv) With the increase of excitation energy, the <ν> vale increases in a similar way in both the reactions. (v) The changing trend of ⟨AL⟩ and ⟨AH⟩ values with the increase of excitation energy are entirely different in between the two reactions.

Selection of dopants and doping sites in semiconductors: the case of AlN

The choices of proper dopants and doping sites significantly influence the doping efficiency. In this work, using doping in AlN as an example, we discuss how to choose dopants and doping sites in semiconductors to create shallow defect levels. By comparing the defect properties of CN, ON, MgAl, and SiAl in AlN and analyzing the pros and cons of different doping approaches from the aspects of size mismatch between dopant and host elements, electronegativity difference and perturbation to the band edge states after the substitution, we propose that MgAl and SiAl should be the best dopants and doping sites for p-type and n-type doping, respectively. Further first-principles calculations verify our predictions as these defects present lower formation energies and shallower defect levels. The defect charge distributions also show that the band edge states, which mainly consist of N- s and p orbitals, are less perturbed when Al is substituted, therefore, the derived defect states turn out to be delocalized, opposite to the situation when N is substituted. This approach of analyzing the band structure of the host material and choosing dopants and doping sites to minimize the perturbation on the host band structure is general and can provide reliable estimations for finding shallow defect levels in semiconductors.

Selenic Acid Etching Assisted Atomic Engineering for Designing Metal-Semimetal Dual Single-Atom Catalysts for Enhanced CO2 Electroreduction.

Single-atom catalysts are promising for electrocatalytic CO2 conversion but face challenges in controllable syntheses. Herein, a facile selenic acid etching-assisted strategy has been developed to fabricate a hybrid metal-semimetal dual single-atom catalyst for electrocatalytic CO2 reduction. This strategy enables the simultaneous generation of monodisperse active sites and hierarchical morphologies with hollow nanostructures. The as-obtained catalyst with Fe-Se dual single-atom sites supported by porous nitrogen-doped carbon (FeSe-NC) shows exceptional catalytic activity and CO selectivity, delivering a Faradaic efficiency (FE) of >97% with industrially comparable jCO, superior to the Fe single-atom catalyst. Moreover, the FeSe-NC-based rechargeable Zn-CO2 battery delivers a high power density (2.01 mW cm-2) and outstanding FECO (>90%), as well as excellent cycling stability. Experimental results together with theoretical calculations reveal that the etching-induced defects and the Se-modulated Fe centers with asymmetrical polarized charge distributions synergistically facilitate the key intermediate *CO desorption and thus accelerate the CO2-to-CO conversion.

Alkali-decorated carbon nitride enhances the removal of enrofloxacin by ferrihydrite-H2O2 system: Mechanistic insights and degradation pathways

Antibiotic pollution affects water quality. Based on the ferrihydrite-H2O2 (Fh-H2O2) photo-Fenton system, alkali-decorated carbon nitride was introduced, and KC3N4/Fh, with ·OH and ·O2− as the primary reactive oxygen species, was synthesized for the degradation of veterinary antibiotic enrofloxacin in water. The modification with KOH induced the formation of cyano groups and nitrogen vacancies in KC3N4/Fh. The presence of cyano groups altered the original charge distribution and energy band structure of the material, thereby establishing an internal electric field. Directed driving of nitrogen vacancies accelerated the transfer of photogenerated charges from the conduction band of KC3N4 to the surface of Fh, facilitating the cycle process of Fe(III) and Fe(II). Meanwhile, the nitrogen vacancies significantly enhanced the adsorption capacity of KC3N4/Fh for H2O2 and accelerated the reaction between the generated Fe(II) and H2O2 to produce ·OH, which subsequently led to the efficient degradation and mineralization of enrofloxacin. The results demonstrated that the degradation rate of enrofloxacin by KC3N4/Fh reached 95.96 % within 30 min, highlighting its high efficiency and stability. Furthermore, KC3N4/Fh exhibited effective degradation of actual effluent under sunlight. This work proposes a novel approach to creating a Fh-H2O2-based photo-Fenton system for the efficient antibiotic degradation.

Design and characterization of defined alpha-helix mini-proteins with intrinsic cell permeability

Proteins with intrinsic cell permeability that can access intracellular targets represent a promising strategy for novel drug development; however, a general design principle is still lacking. Here, we established a library of 46,678 de novo-designed mini-proteins and performed cell permeability screening via phage display. Analyses revealed a characteristic neighboring distribution of positive charges across helices among enriched mini-proteins of CPP7, CPP11, CPP55, CPP109 and CPP112. Compared with the state-of-the-art cell-penetrating mini-protein ZF5.3, the optimized mini-protein CPP11D36R exhibited a sevenfold increase in cell permeability. Endocytosis uptake and early endosome release are the key penetrating mechanisms. A machine learning model with high-throughput data achieved an F1 score of 0.41, significantly outperforming the previously reported CPP prediction models, including MLACP, CPPpred and CellPPD, by 41 %. Overall, our findings validate the effectiveness of a helical structure with a cationic distribution as a design principle on a large scale and present a robust approach for the development of cell-permeable mini-protein drugs.

Large eddy simulations of electrification of liquid dielectrics in channel flow

In this paper we present a computational study of electrification of liquid dielectrics in channel flow and at moderate turbulence intensities. For purposes of computational savings this study consists of large eddy simulations, according to which the large turbulent scales are directly resolved by the computational grid while the effect of the smaller unresolved scales is suitably modeled. First we examine different subgrid-scale models for the electric charge density. Their efficacy is then assessed via comparisons with results from direct numerical simulations at low turbulence intensities. According to our comparisons and analysis, the most efficient model is the one based on the eddy diffusivity approach and the introduction of the turbulent electric Schmidt number. Subsequently, we present numerical results of electrification of benzene in channel flow and at different Reynolds numbers. Herein we discuss the various stages of the electrification process and the variation of the total charge and streaming current with the turbulence intensity. According to our findings, the increase of the turbulence intensity rises dramatically not only the amount of charge transported in the bulk of the fluid but also the rate at which this transport takes place. Finally, we present results for the statistics of the charge density, which provide additional insight about the distribution of the electric charges in the liquid.

Relativistic Modeling of Charged Anisotropic Stars in a Buchdahl Spacetime

In this paper, we studied the behavior of relativistic objects with charged anisotropic matter distribution with a linear equation of state considering a metric potential proposed for Buchdahl (1959). The new solutions to the Einstein-Maxwell system of equations are found in term of elementary functions. A physical analysis of electromagnetic field indicates that is regular in the origin and well behaved. The new obtained models satisfy all physical requirements of a physically reasonable stellar object. The models are consistent with the upper limit on the mass of compact stars for PSR J1823-3021G, PSR J1748- 2446an and PSR J1518+4904.

Macroscopic observation of a first order one-dimensional swelling-deswelling transition in a nanolayered material

AbstractThe high purity and superior quality of the synthetic clay mineral fluorohectorite allows for studies of phenomena that are masked by imperfections and the inhomogeneous charge distribution in the case of natural clay minerals. We have exploited this opportunity offered by synthetic fluorohectorite and report here digital optical microscopy observations of salinity controlled macroscopic swelling and deswelling behavior of extra-large nanolamellar clay mineral particle accordions of various sizes. We find that clay particle accordions, immersed in a saline solution, at sufficiently high salinity, are in their crystalline swelling region, with only a few water layers hydrating the accordion interlayer nano-spaces, corresponding to an interlayer spacing of about 1.5 nm. Using a micropipette as a micro-tweezer and thereby transferring accordions carefully back and forth between high and low salinity solutions, we observe well defined macroscopic accordion transitions between the crystalline swelling regime and an osmotic swelling regime where the interlayer spacings reach tens of nanometers, calculated from accordion thicknesses measured by digital imaging. The transitions display a clear first order character as evidenced by threshold salinity levels for their abrupt onsets as well as clear hysteresis with retention of crystalline or osmotic state memory, as salinity is increased or lowered. The experimental observations are supported by a theoretical model of the accordion interlayer spacing based on a Donnan equilibrium originating from the salinity gradient between the embedding saline solution and the ionic strength in the clay interlayers in the osmotic swelling regime.

Synthesis, spectroscopic, computational, topology, and molecular docking studies on N,N'-(4-methyl-1,3-phenylene)bis(1-(2,4-dichlorophenyl)methanimine)

The study extensively examined N,N'-(4-methyl-1,3-phenylene)bis(1-(2,4-dichlorophenyl)methanimine) (6D). Advanced spectroscopic techniques, including IR, Raman, NMR, and UV-VIS spectroscopies, were employed to analyse the molecule. The Schiff base was ultimately confirmed using NMR spectrum analysis. The UV-VIS study revealed a notable bathochromic change in the compound, indicating their electronic transitions. By using the HOMO–LUMO bond gap the titled compound reactivity sites were identified. The compound 6D HOMO–LUMO band gap is 3.70 eV. Various wave function investigations like MESP, HOMO–LUMO, RDG, ELF, LOL, and ALIE were conducted to elucidate the distribution of electronic charge, providing valuable insights into the behaviour of molecules. The biological probability of the synthesised compound was extensively assessed using a docking study. Using MEP and HOMO–LUMO investigations, we confirm nucleophilic and electrophilic attacking sites. In the docking study, the protein Bovine cytochrome bc1 complex stigma Tellin bound (PDB ID–1PP9) was downloaded. The docking study identified the most stable minimum binding energy is –6.26 kcal/mol.

A Computational Analysis of the Proton Affinity and the Hydration of TEMPO and Its Piperidine Analogs.

The study investigated the impact of protonation and hydration on the geometry of nitroxide radicals using B3LYP and M06-2X methods. Results indicated that TEMPO exhibited the highest proton affinity in comparison to TEMPOL and TEMPONE. Two pathways contribute to hydrated protonated molecules. TEMPO shows lower first enthalpies of hydration (ΔH1-M), indicating stronger H-bonding interactions, while TEMPONE shows higher values, indicating weaker interactions with H2O. Solvent effects affect charge distribution by decreasing their atomic charge. Spin density (SD) is primarily concentrated in the NO segment, with minimal water molecule contamination. Protonation increases SD on N-atom, while hydration causes a more pronounced redistribution for water molecules. The stability of the dipolar structure (>N⋅+-O-) is evident in SD redistributions. The frontier molecular orbital (FMO) analysis of TEMPONE reveals a minimum EHOMO-LUMO gap (EH-L), enhancing the piperidine ring's reactivity. TEMPO is the most nucleophilic species, while TEMPONE exhibits strong electrophilicity. Transitioning from NO radicals to protonated forms increases the EH-L gap, indicating protonation stabilizes FMOs. Increased water molecules make the molecule less reactive, while increasing hydration decreases this energy gap, making the molecule more reactive. A smaller EH-L gap indicates the compound becomes softer and more prone to electron density and reactivity changes.

On a Study of Photoionization of Atoms and Ions from Endohedral Anions

We study the relationship between the results of two qualitatively different semi-empirical models for photoionization cross sections, σnℓ, of neutral atoms (A) and their cations (A+) centrally encapsulated inside a fullerene anion, CNq, where q represents the negative excess charge on the shell. One of the semi-empirical models, broadly employed in previous studies, assumes a uniform excess negative charge distribution over the entire fullerene cage, by analogy with a charged metallic sphere. The other model, presented here, considers the quantum states of the excess electrons on the shell, determined by specific n and ℓ values of their quantum numbers. Remarkably, both models yield similar photoionization cross sections for the encapsulated species. Consequently, we find that the photoionization of the encapsulated atoms or cations inside the CNq anion is influenced only slightly by the quantum states of the excess electrons on the fullerene cage. Furthermore, we demonstrate that the influence decreases even further as the size of the fullerene cage increases. All this holds true at least under the assumption that the encapsulated atom or cation is compact, i.e., its electron density remains primarily within itself rather than being drawn into the fullerene shell. This remarkable finding results from Hartree–Fock calculations combined with a popular modeling of the fullerene shell which is simulated by an attractive spherical annular potential.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Harnessing the Unconventional Cubic Phase in 2D LaNiO3 Perovskite for Highly Efficient Urea Oxidation

AbstractPhase engineering is a critical strategy in electrocatalysis, as it allows for the modulation of electronic, geometric, and chemical properties to directly influence the catalytic performance. Despite its potential, phase engineering remains particularly challenging in thermodynamically stable perovskites, especially in a 2D structure constraint. Herein, we report phase engineering in 2D LaNiO3 perovskite using the strongly non‐equilibrium microwave shock method. This approach enables the synthesis of conventional hexagonal and unconventional trigonal and cubic phases in LaNiO3 by inducing selective phase transitions at designed temperatures, followed by rapid quenching to allow precise phase control while preserving the 2D porous structure. These phase transitions induce structural distortions in the [LaO]+ layers and the hybridization between Ni 3d and O 2p states, modifying local charge distribution and enhancing electron transport during the six‐electron urea oxidation process (UOR). The cubic LaNiO3 offers optimal electron transport and active site accessibility due to its high structural symmetry and open interlayer spacing, resulting in a low onset potential of 1.27 V and a Tafel slope of 33.1 mV dec−1 for UOR, outperforming most current catalysts. Our strategy features high designability in phase engineering, enabling various electrocatalysts to harness the power of unconventional phases.

Engineered interface charges and traps in GaN metal-oxide-semiconductor field-effect transistors providing high channel mobility and E-mode operation

Abstract This review focuses on controlling interface charges and traps to obtain minimal channel resistance and stable enhancement-mode operation in GaN metal-oxide-semiconductor field-effect transistors. Interface traps reduce the free electron density and act as Coulomb scattering centers, thus reducing the channel mobility. Oxide traps cause instability of threshold voltage (V th) by trapping electrons or holes under gate bias. In addition, the V th is affected by the overall distribution of interface charges. The first key is a design of a bilayer structure to simultaneously obtain good insulating properties and interface properties. The other key is the optimization of post-deposition annealing to minimize oxide traps and interface fixed charges. Consequently, the gate structure of an AlSiO/AlN/p-type GaN has been designed. Reductions in V th as a result of polarization charges can be eliminated by using an m-plane trench channel, resulting in a channel mobility of 150 cm2V–1s–1 and V th of 1.3 V.

DFT Computation, Spectroscopic, Hirshfeld Surface, Docking and Topological Analysis on 2,2,5‐Trimethyl‐1,3‐Dioxane‐5‐Carboxylic Acid as Potent Anti‐Cancer Agent

ABSTRACTThe 2,2,5‐trimethyl‐1,3‐dioxane‐5‐carboxylic acid (TDCA) using both theoretical and experimental methods have been studied. The sample has been subjected to XRD, FTIR, FT‐Raman, (C13 and H1) NMR, and UV–vis spectrum analysis. Then, theoretical calculations have been performed at the DFT/B3LYP/6‐311++G(d,p) higher based scale. The theoretical and experimental geometrical parameters and frequencies have been compared well. Theoretical and experimental NMR chemical shifts have been determined. Absorption wavelengths of UV–Vis spectrum were experimentally measured and compared with TD‐DFT predictions. Detailed explanations have been given for frontier molecular orbitals, low density gradient, distribution of Mulliken charges, molecular electrostatic potential (MEP), RDG, localized orbital location, and electron localized activities. Based on the studied 2D image of the Hirschfield surfaces, H···H (65.6%) and O···H/H···O (33.6%) are found as the controlling interactions. A high binding affinity of −6.5 Kcal/mol has been calculated against 4OAR protein. These theoretical findings of the molecule may be used as an anticancer drug candidate, which helps to explain the structural stability, reactivity and anticancer potential of TDCA. High drug affinity for the TDCA has been detected by in silico ADMET prediction.

Self-adaptive reconstructed high-entropy sulfide catalysts with optimized surface electronic structure for lithium-oxygen batteries

Nonaqueous lithium-oxygen batteries have attracted immense attention owing to their high theoretical energy density. High-entropy based materials, encompassing both high-entropy alloys and high-entropy oxides (sulfides), have emerged as promising candidates for cathode catalysts. However, current fabrication methods for high-entropy materials, particularly high-entropy sulfides, remain complex and expensive. And the catalytic mechanism of high-entropy sulfides under oxygen-mediated reactions remains elusive and warrants further investigation. Herein, we propose a novel synthesis method for high-entropy sulfides, involving a hydrogel-xerogel conversion followed by a duplex treatment (low-temperature sulfuration and high-temperature calcination) processes. The synthesized (CoFeNiMnCu)9S8 high-entropy sulfide catalyst achieves elemental equilibrium and exhibits an optimized surface charge distribution. During oxygen-based battery reactions, the catalyst undergoes self-adaptive surface reconstruction, resulting in the formation of a nanoscale polycrystalline layer. This surface modification facilitates charge transfer between Co and Ni elements, and further modulates the localized electronic structure. Benefiting from the reconstructed (CoFeNiMnCu)9S8 cathode catalysts, lithium-oxygen batteries exhibit high reversible specific capacity (15100 mAh g−1), good rate capability, and enhanced long-term cycling stability.

Toward an Enhanced Hydrophilic TiO2 Nanoparticles Adsorption at Air-Liquid Interface Through Ion Regulation.

This study investigates the dynamic properties of air-liquid interfacial tension for hydrophilic TiO2 P25 utilizing the pendant drop method. Additionally, it examines the interfacial adsorption mechanism of hydrophilic TiO2 particles, considering the characteristics of particle surface charge distribution in relation to ion regulation to enhance particle interface adsorption. Experimental results reveal that in the absence of ion addition, the TiO2 P25 suspension system exhibits limited interfacial adsorption due to its superhydrophilicity, regardless of particle concentration. The addition of NaCl increases the surface charge density of the particles, strengthens the electrostatic attraction between particles and the interface, and enhances particle adsorption. Specifically, at a low NaCl concentration (0.01 wt %), the increased surface charge density and contact angle of the particles elevate particle activity and high interfacial packing density. At a higher NaCl concentration (0.1 wt %), while NaCl further increases the particle contact angle, the increased effective cross-sectional area of the air-liquid interface occupied by individual particles leads to a reduction in surface free energy. Despite the enhanced electrostatic attraction, this results in a lower packing density.