Theoretical Study Research Articles

Selective Capture and Manipulation of DNA through Double Charged Nanopores.

In the past few decades, nanometer-scale pores have been employed as powerful tools for sensing biological molecules. Owing to its unique structure and properties, solid-state nanopores provide interesting opportunities for the development of DNA sequencing technology. Controlling DNA translocation in nanopores is an important means of improving the accuracy of sequencing. Here we present a proof of principle study of accelerating DNA captured across targeted graphene nanopores using surface charge density and find the intrinsic mechanism of the combination of electroosmotic flow induced by charges of nanopore and electrostatic attraction/repulsion between the nanopore and ssDNA. The theoretical study performed here provides a new means for controlling DNA transport dynamics and makes better and cheaper application of graphene in molecular sequencing.

Study results in curvilinear motion of high-speed track machine with electromechanical transmission

Introduction. Transport and technological means based on tracked undercarriages have found their use in both military and civilian industries. Their widespread use is due to a number of advantages that contribute to the further development of mechanization of production, increasing the efficiency of transportation of minerals, and developing infrastructure during the development of new territories. Ensuring cross-country ability and mobility of vehicles with tracked undercarriages, including tracked conveyor-tractors, is possible through the use of hybrid electromechanical transmissions. One of the components of scientific research in this direction is carrying out simulation modeling of the movement of equipment. Modeling the motion process will make it possible to substantiate the energy characteristics of the electromechanical transmission of a tracked vehicle and confirm the adequacy of previously performed theoretical studies.Research methods. The main objective of the simulation was to confirm the effectiveness of the theoretical studies performed. The studies in the VISSIM programming environment using typical motion cycles that equivalently reflect the operating conditions and use of a tracked machine were carried out.Results. As a result of the research, quantitative estimates of the influence of the power of a diesel generator and the charge of an energy storage device on the dynamic performance of equipment were obtained. It has been established that in order to meet the requirements for promising samples, the power of the energy storage device should be at least 2.5 kWh when using a standard internal combustion engine.Discussion and conclusion. The research results can be used to create, based on the existing scientific and technical background, a promising robotic complex with an electromechanical transmission.

Theoretical study of the electron-induced vibrational excitation of H2O

This study presents calculations for cross sections of the vibrational excitation of $ H O X A_1 via electron impact. The theoretical approach employed here is based on first principles only, combining electron-scattering calculations performed using the UK R-matrix codes for several geometries of the target molecule, three-dimensional (3D) vibrational states of H$_2$O, and 3D vibrational frame transformation. The aim is to represent the scattering matrix for the electron incident of the molecule. The vibrational wave functions were obtained numerically, without the normal-mode approximation, so that the interactions and transitions between vibrational states assigned to different normal modes could be accounted for. The thermally averaged rate coefficients were derived from the calculated cross sections for temperatures in the 10-10000 K interval and analytical fits for rate coefficients were also provided. We assessed the uncertainty estimations of the obtained data for subsequent applications of the rate coefficients in modelling the non-local thermal equilibrium (non-LTE) spectra of water in various astrophysical environments.

Additive-Driven Nanoscale Architecture of Solid Electrolyte Interphase Revealed by Cryogenic Transmission Electron Microscopy.

In Li metal batteries (LMBs), which boast the highest theoretical capacity, the chemical structure of the solid electrolyte interphase (SEI) serves as the key component that governs the growth of reactive Li. Various types of additives have been developed for electrolyte optimization, representing one of the most effective strategies to enhance the SEI properties for stable Li plating. However, as advanced electrolyte systems become more chemically complicated, the use of additives is empirically optimized. Indeed, their role in SEI formation and the resulting cycle life of LMBs are not well-understood. In this study, we employed cryogenic transmission electron microscopy combined with Raman spectroscopy, theoretical studies including molecular dynamics (MD) simulations and density functional theory (DFT) calculations, and electrochemical measurements to explore the nanoscale architecture of SEI modified by the most representative additives, lithium nitrate (LiNO3) and vinylene carbonate (VC), applied in a localized high-concentration electrolyte. We found that LiNO3 and VC play distinct roles in forming the SEI, governing the solvation structure, and influencing the kinetics of electrochemical reduction. Their collaboration leads to the desired SEI, ensuring prolonged cycle performance for LMBs. Moreover, we propose mechanisms for different Li growth and cycling behaviors that are determined by the physicochemical properties of SEI, such as uniformity, elasticity, and ionic conductivity. Our findings provide critical insights into the appropriate use of additives, particularly regarding their chemical compatibility.

Iron(I) Complex Bearing an Open-Shell Diazenido Ligand.

Low-valent transition-metal diazenido species are important intermediates in transition-metal-mediated dinitrogen reduction reactions. Isolable complexes of the type unanimously feature closed-shell diazenido ligands. Those bearing open-shell diazenido ligands have remained elusive. Herein, we report the synthesis, characterization, and reactivity of a d7 iron(I) complex featuring an open-shell silyldiazenido ligand, [(ICy)Fe(NNSiiPr3)(η2:η2-dvtms)] (1, ICy = 1,3-dicyclohexylimidazole-2-ylidene, dvtms = divinyltetramethyldisiloxane). Complex 1 is prepared in good yield by silylation of the iron(-I)-N2 complex [K(18-crown-6)][(ICy)Fe(N2)(η2:η2-dvtms)] with iPr3SiOTf and has been fully characterized by various spectroscopic methods. Theoretical studies, in combination with characterization data, established an S = 1/2 ground spin-state for 1 that can best be described as a quartet iron(I) center featuring an antiferromagnetically coupled triplet silyldiazenido ligand. The diazenido and alkene ligands in 1 are labile, as indicated by the facile disproportionation reaction of 1 at ambient temperature to transform into the iron(II) bis(diazenido) species [(ICy)(NNSiiPr3)2Fe(dvtms)Fe(NNSiiPr3)2(ICy)] (2) and the iron(0) species [(ICy)Fe(η2:η2-dvtms)] and also the alkene-exchange reaction of 1 with PhCH═CHBC8H14 to form [(ICy)Fe(NNSiiPr3)(η2-trans-PhCH═CHBC8H14)] (3). Complex 1 is light-sensitive. Upon photolysis, it undergoes a SiiPr3 radical-transfer reaction to yield [(ICy)Fe(σ:η2-MeCHSiMe2OSiMe2CH═CHSiiPr3)] (4) and N2. The reactions of 1 with the trityl radical and organic bromides yield iron(II) complexes, which indicates its reducing nature. Moreover, 1 is a weak hydrogen-atom abstractor, as indicated by its inertness toward HSi(SiMe3)3 and cyclohexa-1,4-diene and the low calculated N-H bond dissociation energy (48 kcal/mol) of its corresponding iron(II) iso-hydrazenido species.

Theoretical calculations and molecular modelling of isoindoline compounds as anticonvulsant agents

The lack of safe and effective antiepileptic drugs is a persistent issue that could be addressed through the repurposing or further development of commonly available drugs. Due to high accuracy, low effort, and high cost, it is best to begin the search for alternative treatments with a theoretical chemical study. Isoindoline derivatives, their ΔG, and their molecular docking were subjected to the molecular level theory. Having a ΔG of -4.9, compound A1 demonstrated a unique activity against protein 1OHV (4-aminobutyrate-aminotransferase; from pig), while the same compound demonstrated distinct activity against protein 3F8E (coumarins as suicide carbonic anhydrase inhibitors) with a ΔG of -4.533. Moreover, compound A3 exhibited a unique activity against protein 6KZP (calcium channel-ligand) with a ΔG of -7.597. The undertaken DFT analysis determined the highest occupied molecular orbital (HOMO), the least unoc¬cupied molecular orbital (LUMO), and the HOMO-LUMO gap values for the studied derivatives (compound A1: -0.202, -0.091, and -0.111 eV; compound A3: -0.228, -0.102, and -0.126 eV, respectively). The ionization potential, the soft¬ness, the hardness, and other chemical properties of these compounds were subsequently computed. Drug likeness predictions were employed in order to show that the compounds adhered to Lipinski’s rule. Our results indicate that the molecular mass, log P, as well as the hydrogen bonding donors and acceptors of the herein assessed isoindoline compounds fall within acceptable ranges.

Theoretical calculations and molecular design of novel dioxoisoindoline derivatives as anticonvulsant agents

Our study discusses the need for the development of alternative treatments for antiepileptic drugs. It proposes a theoretical chemical study using dioxoisoindoline derivatives and molecular docking in order to find potential alterna¬tive drugs. Three compounds (S1, S3, and S4) exhibited distinct activity against specific proteins related to epilepsy treatment. Our study also describes a DFT study that analysed the energy levels of the derivatives. Furthermore, we employed Lipinski’s rule and drug likeness predictions in order to assess the suitability of the derivatives as medicines. The results indicate that the molecular mass, log P, hydrogen bonding donors, and acceptors of the compounds fall within acceptable ranges. Overall, our study emphasizes the importance of finding new treatments for epilepsy, and presents a preliminary investigation into the potential of dioxoisoindoline derivatives.

An experimental and theoretical study to evaluate Al2O3–PbO–B2O3–SiO2–BaO radiation shielding properties

This study's objective is to evaluate an Al2O3–PbO–B2O3–SiO2–BaO glass system's radiation shielding characteristics. The composition of the glasses is 15Al2O3–25PbO–(60-x)B2O3–10SiO2–xBaO, with x in the 5–20 mol% range. Experimental results were used to determine the samples' linear attenuation coefficients (LAC), which were then confirmed by Phy-X program. Utilizing narrow beam transmission geometry, the experimental LAC values were determined. According to the results there was high agreement when comparing the theoretical and experimental values. The LAC values were used to calculate the prepared glasses' mass attenuation coefficients (MAC) and other relevant properties. The mean free path (MFP) values of the sample with 5 mol% BaO were 0.079, 2.549, 3.944 and 4.273 cm at 0.0595, 0.662, 1.173, and 1.332 MeV, thus demonstrating that raising the glass system's BaO enhances the prepared glasses' shielding capacity. According to radiation protection efficiency (RPE), the glasses' capacity to shield the photon is enhanced when their BaO content rises.

Study on β-glucosidase activators by 3D-QSAR, molecular docking and molecular dynamics simulation

To investigate the conformational relationship and mechanism of action of β-glucosidase (BGL) activators, a theoretical study of three-dimensional quantitative structure activity relationship, molecular docking, molecular dynamics (MD) simulations, and binding free energy analysis were performed. The results indicate that comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) models had good stability and predictive ability, with r2cv/ r2pred values of 0.540/0.998 and 0.654/0.993, respectively. The derived contour maps of steric, electrostatic, and hydrogen bond donor field further displayed the modified information of these activators. Molecular docking and MD were performed on calcium diascorbate (CaAS) and L-Ascorbyl 2,6-Dipalmitate (L-ADP), which have good activating ability. The study indicates a positive interaction between the activators and the enzyme, and this interaction does not cause irreversible negative effects on the conformation of BGL. The MD results show that the total binding free energies of CaAS and L-ADP with BGL were −19.837 kJ/mol and −37.798 kJ/mol, respectively, and the binding force of the activators with BGL was mainly derived from hydrophobic interaction and hydrogen bonding. This study offers important guidance for the efficient use of BGL and for the research and development of effective activators.

[Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] half-sandwich complexes: Synthesis, solid-state structure, hirshfeld surface analysis and theoretical studies

Indenyl-titanium trichloride complexes of type [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl3] (R = SiMe3 (3a); R = tBu (3b)) were obtained by treatment of Li[1-(SiMe3)-3-(R)-C9H5] (R = SiMe3 (1a); R = tBu (1b)) with titanium tetrachloride (2) in a 1:1 molar ratio in the presence of isopropanol and SOCl2. Compounds [Ti{η5-1-(SiMe3)-3-(R)-C9H5}Cl2(OEt)] (R = SiMe3 (4a); R = tBu (4b)) are accessible by reacting 1a,b (R = SiMe3 (1a); R = tBu (1b)) with TiCl4 (2) in the presence of ethanol and SOCl2, or when 3a,b were treated with equimolar amounts of EtOH in refluxing benzene. Spectroscopic methods and single crystal X-ray diffraction analysis confirmed the piano-stool geometry of 3a and 4b in the solid state. Hirshfeld surface analysis using 2D fingerprint plots of 3a and 4b were conducted to elaborate non-covalent, intermolecular interactions existing in the solid state, which accounted for the strengthening of the crystal lattice. The molecular structures of the 3 and 4 were further investigated by quantum-chemical calculations. The geometries of the compounds were optimized at the B3LYP/6-31G(d)+LANL2DZ level of theory, and their related molecular parameters including frontier orbital energy gap and molecular electrostatic surface potential have also been calculated to better understand their properties.

Theoretical study on photoelectric properties of ferroelectric photovoltaic perovskite CsGeBr3 based on first-principle calculations

Abstract Ferroelectric photovoltaic materials with intrinsic spontaneous polarization have attracted great attention because the ferroelectric polarization can promote the directional migration of electrons and holes, and reduce the trend of carrier recombination. Recently, the evidence of ferroelectricity in the typical three-dimensional all-inorganic halide perovskites CsGeX3, with band gaps of 1.6 eV to 2.3 eV has been confirmed. But the spontaneous polarization of ferroelectric perovskite CsGeX3 is ~10 to 20 μc/cm2 which is weaker than that of ABO3 (~26 to 75 μc/cm2). Strain engineering has a significant influence on the ferroelectric polarization of semiconductor materials by controlling the lattice scaling and the internal atomic spacing. Hence, in this work, strain engineering is introduced to enhance the ferroelectric polarization and maintain the photovoltaic properties of ferroelectric perovskite CsGeBr3. In this paper, we studied the ferroelectric polarization and photoelectric properties of ferroelectric perovskite CsGeBr3 under different triaxial compressive strain based on first-principle calculations. The calculated results show that when the applied compressive strain increases from 0% to -4%, the spontaneous polarization of ferroelectric perovskite CsGeBr3 increases from 14.23 μc/cm2 to 51.61 μc/cm2, and the band gap reduces from 2.3631 eV to 1.5310 eV. The effective mass of electrons and holes gradually reduces, exciton binding energies decrease from 48 meV to 5 meV, and the optical absorption coefficient is strongly enhanced from 3×105 cm-1 to 5×105 cm-1 in visible range. Besides, the power conversion efficiency(PCE) of CsGeBr3 is significantly increased from 16.95% to 26.77%. Therefore, the results indicate that the application of compressive strain can increase the ferroelectric polarization and even improve the original photovoltaic performance of ferroelectric perovskite CsGeBr3. Our theoretical calculations can provide useful insights and beneficial guidance into experimental studies of ferroelectric perovskites in photoelectric applications.

Ionic Pairs-Engineered Fluorinated Covalent Organic Frameworks Toward Direct Air Capture of CO2.

The covalent organic frameworks (COFs) possessing high crystallinity and capability to capture low-concentration CO2 (400ppm) from air are still underdeveloped. The challenge lies in simultaneously incorporating high-density active sites for CO2 insertion and maintaining the ordered structure. Herein, a structure engineering approach is developed to afford an ionic pair-functionalized crystalline and stable fluorinated COF (F-COF) skeleton. The ordered structure of the F-COF is well maintained after the integration of abundant basic fluorinated alcoholate anions, as revealed by synchrotron X-ray scattering experiments. The breakthrough test demonstrates its attractive performance in capturing (400ppm) CO2 from gas mixtures via O─C bond formation, as indicated by the in situ spectroscopy and operando nuclear magnetic resonance spectroscopy using 13C-labeled CO2 sources. Both theoretical and experimental thermodynamic studies reveal the reaction enthalpy of ≈-40kJmol-1 between CO2 and the COF scaffolds. This implies weaker interaction strength compared with state-of-the-art amine-derived sorbents, thus allowing complete CO2 release with less energy input. The structure evolution study from synchrotron X-ray scattering and small-angle neutron scattering confirms the well-maintained crystalline patterns after CO2 insertion. The as-developed proof-of-concept approach provides guidance on anchoring binding sites for direct air capture (DAC) of CO2 in crystalline scaffolds.

Introducing the Occupational Health and Safety Potential Midpoint Impact Indicator in Social Life Cycle Assessment

Occupational health and safety (OSH) is crucial for sustainable development, recognized by corporations, the European Union, and Sustainable Development Goals. This study introduces a characterization model for OSH in the social life cycle assessment (S-LCA) to support the quantification of OHS along product supply chains and sustainable decision making. The characterization model aims to provide a practical approach for assessing OHS at the product level with actual working hours or recommends a secondary approach with monetary data, when working hours are unavailable, to calculate the Occupational Health and Safety Potential (OHSP). The developed model was tested in a theoretical case study on shirt production in Europe and globally. The case study shows that the European shirt value chain resulted in higher OHSP values than the global shirt values chain. In addition, the model shows which life cycle stages and organizations highly contributed to the OHSP results. In both approaches, the shirt production stage contributed highly. Differences in results emerged based on the calculation approach, underscoring the model’s versatility, because increasing the complexity of calculating the CFs with monetary values will affect the results based on sectorial monetary output. Additionally, the study mentions benefits to the operationalization of social impact assessment and limitations when the developed characterized model is employed. Last, this study aids in offering a tool for organizations to meet the demands of the new Corporate Sustainability Reporting Directive by quantifying and publicizing OHS data.

Bismuth tri-iodide – Graphene 2D material

In recent years, a multitude of 2D materials has been extensively studied, and new ones continue to emerge. Among these, bismuth tri-iodide-graphene material has been reported in both theoretical and experimental studies, displaying intriguing properties. These findings suggest potential photovoltaic applications for BiI3 layers and van der Waals superstructures. In this context, the present work explores the growth of van der Waals superstructures BiI3–graphene, obtained through physical vapor deposition. These structures are achieved by nucleating BiI3 and allowing it to grow on graphene-covered TEM grids and ultra-flat silicon substrates.When the structures are directly grown on grids and substrates covered with graphene, twisted BiI3 structures are formed, leading to Moiré interference, indicating the presence of two or more BiI3 layers and non-uniformity. However, when the structures are grown on grids pre-treated with UV/O3, and then subjected to annealing and post-growth, they become more uniform and aligned, without observable twisting. Structures obtained on substrates with this treatment and post-growth result in thinner layers, as thin as 7.59 ± 0.16 nm, with a roughness of 0.435 ± 0.018 nm. As the thickness decreases, the position of the (003) reflection peak in the diffraction pattern shifts to lower values and broadens, indicating an expansion of the cell along the c-axis. The obtained bandgap values, ranging from 1.55 ± 0.04 to 1.62 ± 0.04 eV, closely align with theoretical predictions. The obtained structures become part of the 2D universe of other similar materials, such as TMDs-graphene, and open up exciting possibilities for new properties and applications.

1,2,3-Triazole-containing azamacrocycles from chiral triazolopeptoids: synthesis and solid-state studies.

Two new chiral 1,2,3-triazole-containing macrocyclic oligoamides (i.e.: triazolopeptoid 4 and 5) were obtained through solid-phase synthesis of linear precursors followed by high dilution macrocyclization reaction. Theoretical (DFT) and spectroscopic (NMR) studies revealed the intricate interplay between the Na-chiral side chains and their conformational attitudes. BH3-mediated reduction of the tertiary amide groups of known 1-3 and newly synthesized 4 gave novel azamacrocycles 6-9. Detection of borane complexes of azamacrocycles 6 and 9 (i.e.: 10 and 11), corroborated by X-ray diffraction studies, demonstrated the peculiar properties of 1,2,3-triazole-containing macrorings.

Ultrahigh energy efficiency from a supersonic underwater ultrasound source

The present work is dedicated to an experimental and theoretical study of an innovative underwater ultrasound source. The source works using a technique in which a pulsed power generator using the impedance mismatch of a long high-voltage coaxial cable generates a train of voltage impulses with a very high pulse repetition frequency of the order of a few MHz. Applying this train of voltage impulses to a pair of underwater electrodes generates a streamer-initiated breakdown of water and, subsequently, a plasma column connecting the electrodes over a very large inter-electrode gap of 55 mm. The interaction of the long plasma column thus formed with the surrounding water produces a rapidly expanding vapor bubble, an “instrument” producing a strong pressure wave with an overall energy efficiency of 24%, an order of magnitude higher than most underwater pressure sources reported in the literature.

Intrinsic negative Poisson’s ratio of the monolayer semiconductor β- TeO2

Monolayer semiconductors with unique mechanical responses are promising candidates for novel electromechanical applications. Here, through first-principles calculations, we discover that the monolayer β- TeO2 , a high-mobility p-type and environmentally stable 2D semiconductor, exhibits an unusual out-of-plane negative Poisson’s ratio (NPR) when a uniaxial strain is applied along the zigzag direction. The NPR originates from the unique six-sublayer puckered structure and hinge-like Te–O bonds in the 2D β- TeO2 . We further propose that the sign of the Raman frequency change under uniaxial tensile strain could assist in determining the lattice orientation of monolayer β- TeO2 , which facilitates the experimental study of the NPR. Our results is expected to motivate further experimental and theoretical studies of the rich physical and mechanical properties of monolayer β-TeO2.

Theoretical investigation of energy levels and transitions for Ce iii with applications to kilonova spectra

ABSTRACT Doubly ionized cerium (Ce2+) is one of the most important ions to understand the kilonova spectra. In particular, near-infrared (NIR) transitions of Ce iii between the ground (5p6 4f2) and first excited (5p6 4f 5d) configurations are responsible for the absorption features around 14 500 Å. However, there is no dedicated theoretical studies to provide accurate transition probabilities for these transitions. We present energy levels of the ground and first excited configurations and transition data between them for Ce iii. Calculations are performed using the grasp2018 package, which is based on the multiconfiguration Dirac–Hartree–Fock and relativistic configuration interaction methods. Compared with the energy levels in the NIST data base (Kramida et al. 2024), our calculations reach the accuracy with the root-mean-square (rms) of 2732 or 1404 cm−1 (excluding one highest level) for ground configuration, and rms of 618 cm−1 for the first excited configuration. We extensively study the line strengths and find that the Babushkin gauge provides the more accurate values. By using the calculated gf values, we show that the NIR spectral features of kilonova can be explained by the Ce iii lines.

Ion Dynamics at the Intermediate Charging State of the Sodium Vanadium Fluorophosphate Cathode.

Na super ionic conductor (NASICON)-type polyanionic vanadium fluorophosphate Na3V2O2(PO4)2F (NVOPF) is a promising cathode material for high-energy sodium-ion batteries. The dynamic diffusion and exchange of sodium ions in the lattice of NVOPF are crucial for its electrochemical performance. However, standard characterizations are mostly focused on the as-synthesized material without cycling, which is different from the actual battery operation conditions. In this work, we investigated the hopping processes of sodium in NVOPF at the intermediate charging state with 23Na solid-state nuclear magnetic resonance (ssNMR) and density functional theory (DFT) calculations. Our experimental characterizations revealed six distinct sodium coordination sites in the intermediate structure and determined the exchange rates among these sites at variable temperatures. The theoretical calculations showed that these dynamic processes correspond to different ion transport pathways in the crystalline lattice. Our combined experimental and theoretical study uncovered the underlying mechanisms of the ion transport in cycled NVOPF and these understandings may help the optimization of cathode materials for sodium-ion batteries.

Height-modulating horizontal transport of dust particles in a dusty plasma ratchet

Abstract Dust particles are often electrostatically trapped and levitated within the non-electroneutral region of a sheath. The fascinating transport phenomena of dust particles strongly depend on the plasma parameters surrounding them within the sheath, whereas, that are quite difficult to obtain, leading to an unclear understanding of particle transport mechanisms. Here, we demonstrate a tunable horizontal transport of micron-sized dust particles by precisely manipulating their vertically suspended heights in an asymmetric ratchet sheath by designing dusty plasma ratchet. A collection of dust particles serves as micro-probes to detect the height-dependent transport properties and the feature of the sheath. Two methods are employed to lift or reduce the suspended heights of dust particles while maintaining the sheath unchanged. As the suspended heights of dust particles vary, their directional transport changes accordingly, including a flow reversal. A two-dimensional (2D) model of the ratchet sheath depicts the nonlinear distributions of plasma parameters and reveals that these unexpected transport phenomena can be attributed to the dependence of the electric ratchet potential and the resulting non-equilibrium net ion drag force on the suspended heights of dust particles. Our combined experimental and theoretical study provides insights into the fundamental transport properties of dust particles in an asymmetrical sheath.