International Journal of Quantum Chemistry最新文献

The cross-linked polyethylene (XLPE) is usually applied in high-voltage direct-current power cable insulation. The electrical conductivity of the insulation material can be increased by the byproducts based on dicumyl peroxide (DCP) process. A new functional structure was designed to prepare XLPE-based insulation materials without byproducts and the reaction mechanism and process were theoretically studied. The reaction potential energy information is obtained at B3LYP/6-311 + G(d,p) level. Results demonstrate that the 3,5-disubstituted acetophenone epoxy-g-Ap-g-epoxy can be used as dual-functional additives of voltage stabilizer and cross-linker. The cross-linking reactivity on the three attacking patterns of nucleophilic reagent is in order of CH site by O on carbonyl groups > CH₂ site by O on carbonyl groups > CH₂ site by O on hydroxyl groups. The byproducts-free dual-functional structure design of XLPE-based insulation PE-g-Ap-g-PE opens up the possibility to replace DCP cross-linking and would be beneficial to further design thermoplastic insulation materials.

The cross-linked polyethylene (XLPE) is usually applied in high-voltage direct-current power cable insulation. The electrical conductivity of the insulation material can be increased by the byproducts based on dicumyl peroxide (DCP) process. A new functional structure was designed to prepare XLPE-based insulation materials without byproducts and the reaction mechanism and process were theoretically studied. The reaction potential energy information is obtained at B3LYP/6-311 + G(d,p) level. Results demonstrate that the 3,5-disubstituted acetophenone epoxy-g-Ap-g-epoxy can be used as dual-functional additives of voltage stabilizer and cross-linker. The cross-linking reactivity on the three attacking patterns of nucleophilic reagent is in order of CH site by O on carbonyl groups > CH₂ site by O on carbonyl groups > CH₂ site by O on hydroxyl groups. The byproducts-free dual-functional structure design of XLPE-based insulation PE-g-Ap-g-PE opens up the possibility to replace DCP cross-linking and would be beneficial to further design thermoplastic insulation materials.

Metal-air batteries stand as a sustainable energy technology; however, their large-scale application is impeded by the high overpotential at cathodes, which compromises cycling stability. Recent investigations have demonstrated that dual-atom catalysts exhibit superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance compared to single-atom counterparts, highlighting the critical importance of rational design for highly active diatomic metal–organic frameworks (TM₂-MOF). Herein, we systematically explored the ORR/OER behaviors of TM₂-MOF catalysts (TM = Cu, Ag, Au, Ni, Pd, and Pt) via first-principles calculations. A combination of structural optimization, stability evaluation, charge density distribution analysis, and thermodynamic free energy computations revealed that Au₂-MOF delivers exceptional catalytic activity, with an extremely low overall overpotential of 0.44 V for ORR/OER processes. This structural innovation not only significantly enhances the catalytic efficiency of TM₂-MOF based catalysts but also provides fundamental insights and novel strategies for advanced electrocatalyst development for metal-air battery.

Accurate modeling of CO adsorption on copper surfaces is essential for catalytic processes such as syngas conversion and methanol synthesis. However, standard generalized gradient approximation (GGA) functionals cannot reproduce physical site preferences due to the “CO adsorption puzzle.” Nonetheless, resolving site preference alone does not ensure a computationally feasible methodology for studying catalytic COCu systems. A systematic approach is required to identify a balanced framework that is both accurate and feasible for large-scale catalytic studies. Thus, this work systematically evaluates the effects of basis sets, exchange functionals, dispersion and Hubbard-U adjustments for CO adsorption on Cu(100), Cu(110), Cu(111), and Cu(211) surfaces using periodic DFT computations. While experimentally observed on-top adsorption can be achieved using the Hubbard-U correction, dispersion corrections only improve adsorption energy agreement with experimental data, not the site preference. Among the tested setups, projector augmented-wave method with the Perdew–Burke–Ernzerhof exchange-correlation (PAW-PBE) with U = 8 eV and Grimme-D3 dispersion correction emerged as a reliable and efficient combination, consistently reproducing adsorption energies and vibrational properties in agreement with experimental reports. To validate this setting in catalytic CO–Cu systems, the approach was extended to methanol adsorption. This work provides a unified, computationally efficient DFT + U + D3 protocol that reproduces experimental CO adsorption behavior and can be readily applied to other catalytic Cu systems.

Although the isomeric energetic compounds DTDA and T-N10B share high sensitivity, DTDA possesses superior thermal stability. Investigations reveal that DTDA's enhanced thermal stability originates from stronger trigger bonds (resulting in a higher initial decomposition energy barrier), greater π-electron delocalization capability, and an effective hydrogen bonding network in the crystal. On the other hand, their shared high sensitivity stems from similar crystal packing imperfections: irregular Hirshfeld surfaces, anisotropic molecular arrangement, and inhomogeneous intermolecular interactions. These structural features collectively restrict energy dissipation under external stimuli, thereby explaining their high sensitivity.

Fluorine is commonly incorporated into pharmaceuticals to enhance properties such as metabolic site blocking. However, the Smoothened receptor (SMO) inhibitor, 2,4-Difluoro-benzylphthalazine derivative, undergoes metabolism by CYP450 to generate toxic quinone species. A combination of reactivity and accessibility is employed to demonstrate that the quinone production involves hydrogen abstraction from benzyl instead of the phenyl epoxidation mechanism. The main metabolite of fluorine-containing benzylphthalazine derivatives is benzyl hydroxylation derivatives, which corroborates well with experimental observations. The rate-determining step in the epoxidation process is a CO bond formation, leading to the production of a radical species instead of a carbocation intermediate. The substitution of F with groups such as CF₃ or CN can increase the energy barrier associated with CO bond formation, thereby augmenting the difficulty in producing quinones. The present study provides a theoretical foundation for the drug metabolism and drug design of pharmaceuticals containing fluorine atoms.

A computational study of dihydrogen-bonded complexes formed by LiH⋯HX (X = F, Cl, CN, or CCH) at the DFT, MP2, and CCSD theoretical levels along with Pople's and Dunning's basis sets is presented. One of our main goals was to establish a direct correlation between interaction strength and the stretching frequencies of the proton donors shifted to red and blue. To this end, NBO and ChElPG atomic charge calculations were performed to quantify intermolecular charge transfers. Considering the wide range of formalisms for atomic charge calculations, the theoretical levels employed, as well as the types of intermolecular bound systems studied in this work, the application of an unsupervised statistical pattern recognition method was required. Furthermore, NCIPlot graphic visualization and QTAIM topological descriptors have characterized all dihydrogen bonds and the intermolecular covalency profile could be discussed in terms of contributions from kinetic and potential energy densities. Additionally, SAPT energy partitioning was used to evaluate the interaction strength and the trend associated with the manifestation of intermolecular covalency.

The development of high-performance n-type thermoelectric materials for application in aerospace energy harvesting systems is the main objective of this work. We present an innovative synthesis approach for ZnAlGaO-based semiconductors, utilizing a refined sol–gel technique with water-based precursor solutions and the inclusion of glacial acetic acid to facilitate gelation. The process carefully controls solution pH and turbidity through precise instrumentation, ensuring the formation of uniform gels. Following gelation, the xerogel undergoes an optimized drying procedure at 200°C to remove residual compounds. High-purity ZnAlGaO materials are then created by calcining the resultant powders at 600°C. A novel thermal process at 1350°C for 36 h was implemented to improve the bulk thermoelectric characteristics of the material. Detailed characterization techniques, including DTA-TG, SEM, FTIR, XRD, XPS, and thermoelectric measurements, confirm the superior performance of the fabricated materials. The n-type ceramics exhibit a remarkable thermoelectric figure of merit of 0.172 at 800°C, making them promising candidates for thermoelectric generator applications in aerospace technologies.

Anthocyanidins are natural compounds soluble in water and known for their various biological activities. They show potent antioxidant activity towards free radicals. Herein, we investigate the effects of different types of polar and nonpolar solvents on the antioxidant activity of pelargonidin 3-glucoside. Density functional theory calculation has been performed using the hybrid functional M052X and the basis set 6-31+G(d,p). The solvent effects were considered implicitly by using IEFPCM formalism where acetone, aniline, benzene, water, methanol, chloroform, and cyclohexane are the attested solvents. The antioxidant activity is evaluated by calculating bond dissociation enthalpies of different OH groups (BDEs) and ionization potentials (IP) of pelargonidin 3-glucoside. In addition, the dipole moment and gap energy in different solvents were determined. The results show that the antioxidant activity of the pelargonidin 3-glucoside increases with polarity and that water is the favored media for free radical scavenging. The results show that an exponential potential decays of ionization potential with the dielectric constant of the tilted solvent. The favorable mechanism involved in free radical scavenging of free radicals by anthocyanidin pelargonidin 3-glucoside may depend on both the environment and the reactants. Herein, the effect of the solvent polarity on the stability of the transition state, activation, and the rate constant of the PC-ET mechanism of OOCH3 free radical scavenging by the pelargonidin 3-glucoside have been investigated. The obtained results showed that the free radical scavenging by 3-glucoside may be strongly affected by the environmental media and the type of solvents, that is, polar or nonpolar solvents.