International Journal of Quantum Chemistry最新文献

The hydration properties of HgCl₂ in water were investigated using quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) simulations. In the first hydration shell, HgCl₂ was coordinated by three water molecules, with an average Hg–O bond distance of 2.60 Å. These water molecules were positioned equatorially around the mercury atom. However, due to frequent ligand exchanges, the geometry of the first hydration shell exhibited a distorted trigonal bipyramidal structure. The mean residence time (MRT) of water molecules in this shell was 1.64 ps, indicating a relatively weak interaction between HgCl₂ and the surrounding water molecules.

This study offers a comprehensive and systematic theoretical investigation into the photophysical properties of new fluorescent nucleobase analogs, specifically ^CF3thG, ^CF3thA, ^CF3thC, and ^CF3thU, utilizing density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. These analogs (CF3th-bases) are generated by trifluoromethylation on the C7 atom of th-bases, and only ^CF3thG has just been synthesized experimentally. The nature of the electronic low-lying singlet transitions are discussed and compared with methylated and unmodified th-bases. The effects of water solution, deoxryribose conjunction, and base pairing were meticulously examined. It was found that trifluoromethylation leads to an increase in adiabatic ionization potentials (AIPs) and a concomitant decrease in HOMO (H)-LUMO (L) gaps, highlighting the significant impact of this modification on the electronic properties of nucleobases. Electronic absorption studies reveal red shifts in the S₁ transition energies of CF3th-bases relative to their parent th-bases, with enhanced oscillator strengths. All CF3th-bases exhibit fluorescence in the visible region. The inner shell water molecules were found to significantly impact the photophysical properties of ^CF3thG-H3. The deoxyribose conjugation introduces bathochromic shifts and enhancements of oscillator strengths in fluorescence emission processes. Base pairing with natural nucleobases maintains structural stability and it will result in the fluorescence quenching of ^CF3thC via an intermolecular charge transfer mechanism in gas phase. These findings highlight the significant impact of trifluoromethylation on the electronic and photophysical properties of th-bases, providing insights into their potential applications in nucleic acid research.

Quantum chemistry is among the most promising areas for quantum computing. In this study, we explored the efficacy of hybrid classical-quantum algorithms in modeling peptide bond dynamics by analyzing the cis-trans isomerization pathway, including an associated transition state. Three different active spaces were validated by coupled cluster calculations and the Qubit Efficient Encoding technique was applied to the chosen active spaces of the amide bond. Energy differences of the cis, trans and an isomerization transition state of the smallest suitable peptide models (N-methylacetamide and H-Gly-Gly-OH) were determined by the VQE method using 3 different hardware efficient ansätze (HEA). The VQE results from different combinations of active spaces and HEAs were compared with the exact results, and their difference converged to 0 kJ·mol⁻¹ as the number of the layers of the ansätze increased and showed that in these cases VQE is applicable to calculate local energetic properties of amides.

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.