International Journal of Quantum Chemistry最新文献

LaTaON₂ is a promising visible-light-responsive photocatalyst for water splitting because of its broad visible light absorption and suitable band edge positions. However, the high defect concentration hinders the charge transfer and results in the poor photocatalytic performance of LaTaON₂. Loading proper cocatalysts is one of the most efficient strategies for promoting charge separation/transfer and achieving high reaction activity. In this work, we have used density functional theory calculations to study the depositions of Pt, Ru, and Ni single atom cocatalysts on LaTaON₂(010) surface. The most stable adsorption configuration is the same site for all the elements, namely the top of the N atom on the La-terminated surface and the fourfold hollow site on the Ta-terminated surface. The adsorption of the metal single atom on Ta-termination is stronger than that on La-termination due to the formation of more bonds. Upon the deposition, no localized impurity states appear in the middle of the forbidden gap since the nd states of metal adatoms are located within the valence band and conduction band of LaTaON₂. The efficiency of the photocatalysts is probed by investigating their ability to adsorb the H atom in a thermodynamically favorable manner. Our results reveal that the energetically favorable sites of HER are the N atom on the La-termination and the O and N atoms on the Ta-termination, respectively. Compared with the clean surface, the surfaces with Pt, Ru, and Ni single adatoms exhibit higher performance for HER because loading metal cocatalysts can further activate the surface nonmetal atoms and reduce the Gibbs free energy of hydrogen adsorption. The work gives an atom-level insight into the role of metal single atom cocatalysts in the LaTaON₂ photocatalyst for hydrogen production.

This manuscript introduces a relativistic method to determine the electronic structure and electron collision ionization process of atoms placed in a semiclassical plasma. The method uses the effective interaction pseudo-potential derived for general two interacting charged particles taking into account the quantum mechanical and screening effects to model the plasma environment. The Dirac equation with the aforementioned pseudo-potential is solved numerically to obtain the bound state and continuous state wave functions. The method starts from the Dirac equation and thus includes the relativistic effects on the one-electron level. The effects coming from the Breit interaction and quantum electrodynamics corrections are included. As a representative example, we investigate the plasma electron screening effect and the plasma ion screening effect, separated and combined, on the level delocalization and electron collision ionization process of hydrogen atoms placed in a strongly coupled semiclassical plasma environment. Properties of the spectra such as energies, oscillator strengths, and relativistic energy shifts corresponding to bound states are determined. The relativistic distorted wave method is used to provide a consistent and elaborate description of the ionization cross sections of the electron collisions involved. Our results reveal that the plasma electron shielding effect contributes to a reduced ionization potential and oscillator strength, while increasing the electron impact ionization cross section, when compared with the results of an isolated scenario. When the plasma ion shielding effect is included, these observed alterations are further enhanced, highlighting the considerable role of the plasma ion shielding effect in this process. Our results are in agreement with other theoretical data. The present study not only extends the relativistic distorted wave approach to the analysis of collision processes in semiclassical plasmas and evaluates the impact of the plasma ion screening effect but also has practical implications for radiation physics, inertial confinement devices, and the interiors of stars.

This research work focuses on the theoretical investigation and evaluation of the biological activities of three medicinal plants: black cumin and Artemisia, which have been widely used in the treatment of coronavirus, and Euphorbia Atlantica Coss, belonging to the Euphorbiaceous family. The molecules that are the subject of our work are: thymol, thymoquinone, thujone, and artemisinin, as well as methyl galat (M1) and pholoroacetophenone 4-O-B-D-glucopyranoside (M2); molecules extracted from the plant Euphorbia Atlantica Coss. Structural and orbital studies are carried out on these species, with the aim of establishing a structure-biological activity relationship. The obtained results an energy gap of the order of ~5.5 eV is found for most of the molecules. Potential electrostatic calculations show that Thymol, M1, and M2 are susceptible to electrophilic attack. Thymol has a high polarizability and therefore a good activity, while a good electronic transfer is observed for thujone and artemisinin. Our study showed that black cumin has much more intense absorbance peaks than other plants. AIM analysis identifies critical points at CO and OH bonds, with strong hydrogen bonding in artemisinin. Molecular docking shows promising inhibitory potential of artemisinin. Assessment of the main ADME properties showed that all compounds except M1 and M2 comply with Lipinski's rule, which predicts good oral bioavailability.

The study investigated the contribution of hydroxymethanesulfonic acid (HMSA) to the formation of new particles in the presence of atmospheric bases such as ammonia (A), methylamine (MA), dimethylamine (DMA) and water (W) by DLPNO-CCSD(T)/aug-cc-pVTZ//B3LYP-D3/aug-cc-pVTZ(aug-cc-pV(T+d)Z for sulfur) level. Clusters containing HMSA were found easily to form six− or eight−membered ring structures via SO—H⋯O (HMSA donor), O—H⋯O/N (W donor), N—H⋯O/N (A/MA/DMA donor), and C—H⋯O (MA/DMA donor) hydrogen bonds. Due to the synergistic interaction between X and Y molecules, the stability of HMSA−X−Y trimers is thermodynamically more favorable than HMSA−X dimers, and proton transfer was found to be exothermic and barrier−free in HMSA−X−Y trimers. Moreover, the stability of HMSA−X−Y trimers increased with higher alkalinity of X and Y, leading to decreased evaporation rates. The study highlights the significance of HMSA−containing trimers in nucleation processes for new particle formation, suggesting their potential role as nucleation centers in atmospheric conditions.

Molecular descriptors are essential tools for analyzing the structural and physicochemical properties of molecular systems. In this study, novel modified reverse degree-sum descriptors are applied to analyze kekulenes, a distinctive class of cycloarenes known for their aromaticity, superaromaticity, and exceptional electronic properties. These descriptors are further integrated with graph entropy measures to evaluate the structural complexity and energetic properties of three kekulene tessellation patterns: Zigzag, armchair, and rectangular. Energetic parameters, including total $��\pi �$-electron energy, HOMO-LUMO energy gaps, and resonance energy, are computed to provide a detailed understanding of the kinetic and thermodynamic stability of these tessellations. The modified reverse degree-sum-based methodology applies to all degree-sum-based descriptors. The variable parameter ‘$��k�$’ adjusts the molecular graph's degree-sum sequence to best fit the unique properties of each dataset. These enhancements strengthen correlations with physicochemical properties, improving the descriptor's effectiveness in structural analysis. Furthermore, regression models are developed to predict the energetic behavior of high-dimensional kekulene structures, offering a robust framework for advanced studies in molecular stability and design.

Sugar, as a denitration agent, has broad application prospects in the field of high-level radioactive liquid waste (HLLW) treatment. Understanding the interaction mechanism between nitric acid and sugar is crucial for the development of HLLW treatment. This study presents a detailed reaction mechanism, revealing key intermediates (HNO₂) and pathways (generation of carboxyl groups) leading to critical products (NO₂, NO, CO₂, and CO). The work shows five different paths leading to the ring-opening of β-D-glucopyranose. The results indicate that the ring-opening path involving the interaction of H₃O⁺ with glycosidic oxygen has the greatest kinetic advantage, with lower energy of highest point (EHP) (63.6 kJ/mol) and lower highest energy barrier (HEB) (49.2 kJ/mol). Furthermore, carbon oxides, as key gaseous products, exhibit a synergistic relationship with the generation pathways of nitrogen oxides, promoting each other. In addition, through thermodynamic analysis of the four reaction products (NO₂, NO, CO₂, and CO), the study shows that the reactions producing NO₂ and NO are spontaneous exothermic reactions, while the reactions generating CO₂ and CO are non-spontaneous endothermic reactions. The study aims to elucidate the atomic-scale interaction mechanism between sugar-based denitration agents and nitric acid, providing a theoretical basis for the application of natural polysaccharides in HLLW, while also opening new avenues for the design of reducing agents and byproduct control strategies in industrial denitration processes.

The effect of ribbon width and edge shape on the electronic and magnetic properties of C₆N₆ nanoribbons has been examined using density functional theory (DFT). The results indicate that all the considered C₆N₆ nanoribbons are energetically stable, and hydrogenation increases their stability while eliminating their magnetic properties. As the ribbon width increases, the energy gap decreases. The findings suggest that the band gap can be tuned by altering the edge shape and ribbon width. Consequently, the studied nanoribbons are promising candidates for optoelectronic and spintronic devices.

Nb₂C has attracted particular attention in the field of elevated temperature, wear resistance, and corrosion resistance, owing to its unique physical and chemical properties. Currently, fewer efforts have been devoted to the exploration of its mechanical properties and thermodynamic response under elevated pressure. As a solution, theoretical calculations were employed to reveal the influence of increased pressure on the structural, mechanical, electronic, and thermodynamic properties of Nb₂C. Elastic moduli were derived from elastic constants, whereas Poisson's ratio, sound velocity, and Debye temperature were determined using the obtained elastic moduli and constants. The investigation focused on the analysis of elastic anisotropy through the utilization of various indexes for elastic anisotropy, as well as the construction of three-dimensional (3D) surfaces and their planar projections. The analysis of the electronic characteristics indicates that Nb₂C displays a metallic behavior. Moreover, the hardness H_v and thermal conductivity k were evaluated by different methods.

The ground-state structures of neutral, monovalent, and divalent anion ScSn_n^0/−/2− (n = 4–17) clusters were calculated by using a global search technique combined with density functional theory, and their spectral properties, electronic configurations, and relative stability were also studied. It is found that the ground-state structures for monovalent anion ScSn_n⁻ (n = 4–17) clusters are similar to those of divalent anions, and the ground-state structures for ScSn_n^−/2− are all adsorption structures obtained by adsorbing one Sn atom on the structures of ScSn_n−1^−/2−. The growth mode of ScSn_n^0/−/2− (n = 4–17) clusters can be divided into three different types of adsorption modes (n = 4–5, n = 6–10 and n = 11–17): ScSn₄^0/−/2− triangular bipyramid structures, ScSn₆^0/−/2− pentagonal bipyramid structures, and ScSn₁₁^0/−/2− single capped anti-pentagonal prism structures are used as base units to adsorb 1–6 Sn atoms, forming adsorption structures. When n = 11, it is the smallest cage structure size. The simulated photoelectron spectra of ScSn_n⁻ clusters are in good agreement with the existing experimental spectra. The infrared, Raman, and ultraviolet spectral properties of ScSn_n^0/−/2− (n = 4–17) clusters were analyzed, and their natural population analysis, dissociation energy, second-order energy difference, and HOMO-LUMO energy gap were also discussed. The results show that the FK-structure ScSn₁₆⁻ cluster not only has good thermodynamic stability and chemical stability, but also exhibits ideal optical properties, which can be used as a potential nano-optical material building block.

The excellent corrosion resistance of high-nitrogen steel is related to the passivation film on its surface. However, the mechanism by which nitrogen and chromium atoms affect the formation of the passivation film remains unclear. Electrochemical test results show that nitrogen and chromium promote the formation of the passivation film and secondary passivation. The calculation results indicate that oxygen atoms tend to adsorb on the Fe(111) surface, and chromium doping enhances the adsorption of oxygen atoms. Nitrogen doping increased the segregation energy of chromium toward the surface by 79.8%, promoting the segregation of chromium toward the surface, which further enhanced the adsorption of oxygen atoms on the Fe(111) surface. The synergistic effect of nitrogen and chromium causes oxygen atoms to rapidly accumulate on the Fe(111) surface, forming a protective passivation film, which is the fundamental source of corrosion resistance. In addition, the d-band center is positively correlated with oxygen adsorption energy, indicating that increasing the d-band center on the surface can enhance the adsorption of oxygen atoms, promote the formation of passivation films, and improve corrosion resistance. These findings provide theoretical insights and strategies for studying and controlling the corrosion resistance of materials.