International Journal of Quantum Chemistry最新文献

Pyrite is the most widely distributed sulfide mineral with a wide range of uses, and pyrite is mainly recovered by means of flotation in practical production, and the commonly used flotation collectors are mainly xanthates with good flotation performance. The adsorption behavior of commonly used collectors ethyl xanthate and butyl xanthate on the surface of pyrite is investigated by using the density functional tight bounding theory (DFTB). The results show that when a single reagent acts on the pyrite surface, butyl xanthate has a stronger effect than ethyl xanthate, and the adsorbed mineral surface shows obvious hydrophobicity. The interaction between ethyl xanthate and butyl xanthate had a stronger effect than that of a single reagent, and the simulation of the flotation environment at ordinary temperature using molecular dynamics revealed that the synergistic adsorption of the two different reagents on the surface of pyrite was more hydrophobic, that is, the synergistic adsorption of the combined collector of ethyl xanthate and butyl xanthate on the surface of pyrite was stronger. The results of the study are of great significance for the synergistic effect between the combined collector and the mineral.

In this paper, the first-principles method is used to calculate the electronic structure of the intrinsic WSe₂ system and the Ca adsorbed WSe₂ system under shear deformation, and the diffusion barrier of Ca on WSe₂ is studied in depth. The results show that shear deformation can effectively reduce the band gap of WSe₂ system, and shear deformation can easily lead to the transition from semiconductor properties to metal properties. The adsorption of Ca leads to the change of the band structure of WSe₂. The contribution of Ca-d electrons leads to an increase in the peak in the range of 3–6 eV. The shear deformation reduces the diffusion barrier of Ca on the WSe₂ surface. This paper provides an improvement method for the application of WSe₂ in the field of battery.

Ionic liquids (ILs) are considered unique and attractive types of solvents with great potential to capture carbon dioxide (CO₂) and reduce its emissions into the atmosphere. On the other hand, carrying out experimental measurements of CO₂ solubility for each new IL is time-consuming and expensive. Whereas, the possible combinations of cations and anions are numerous. Therefore, the preparation and design of such processes requires simple and accurate models to predict the solubility of CO₂ as a greenhouse gas. In the present study, two different models, namely: artificial neural network (ANN) and support vector machine optimized with dragonfly algorithm (DA-SVM) were used in order to establish a quantitative structure–property relationship (QSPR) between the molecular structures of cations and anions and the CO₂ solubility. More than 10 116 CO₂ solubility data measured in various ionic liquids (ILs) at different temperatures and pressures were collected. 13 significant PaDEL descriptors (E2M, MATS8S, TDB6I, TDB1S, ATSC4V, MATS8M, ATSC7V, Gats2S, Gats5S, Gats5C, ATSC6V, DE, and Lobmax), temperature and pressure were considered as the model input data. For the test set data (2023 data point), the estimated mean absolute error (MAE) and R² for the ANN model are of 0.0195 and 0.9828 and 0.0219 and 0.9745 for the DA-SVM model. The results obtained showed that both models can reliably predict the solubility of CO₂ in ILs with a slight superiority of the ANN model. Examination of sensitivity and outlier diagnosis examinations confirmed that the QSPR model optimized using the ANN algorithm is better suited to correlate and predict this property.

As one of the most potent greenhouse gases, SF₆ has a significant economic and environmental impact on the purification and recovery of exhaust gases from the semiconductor industry. The adsorption and separation performance of SF₆ on a two-dimensional covalent organic framework TAT-COFs-1-AB with different functional groups (SO₃H, Et, NH₂, OMe, OH, H) was investigated by using grand canonical Monte Carlo (GCMC) simulations and density functional theory (DFT) calculations. The results show that the adsorption at low pressure depends on the interactions between the SF₆ and COF frameworks, while at high pressure it is mainly affected by the porosity. The highest adsorption capacity of 8.44 mmol/g (298 K, 100 kPa) is exhibited by TAT-COF-1-AB-H, which has the highest porosity. Chemical functionalization was found to be effective in enhancing the SF₆/N₂ selectivity. Among all the functionalized COFs, TAT-COF-1-AB-NH₂, with the highest specific surface area and strong heat of adsorption, showed the highest selectivity. The simulation of self-diffusion also shows consistent results with the GCMC simulation. The findings highlight that the adsorption capacity is influenced by substituent and porosity, with SF₆ showing a consistent preference for adsorption at hollow sites, as evidenced by binding energy and charge transfer analyses.

An intriguing question in the general problem of aromaticity is whether captodative aromatic systems with the donor and acceptor substituents at the same carbon of the CC bond can be more stable than the π-conjugated push-pull counterparts? The analysis of electronic, magnetic, and structural criteria of aromaticity showed that for conventional organic substituents XO, TfN, (NC)₂C, (NO₂)₂C, Tf₂C, the push-pull tropylidene derivatives [tropylium]⁺CHCHX⁻ are expectedly more stable than their captodative isomers [tropylium]⁺C(X⁻)CH₂, with the lowest ΔE for the most strong acceptor Tf₂C. A different behavior is observed for XMHlg₃ (MB, Al; HlgF, Cl). They are not only structurally and magnetically most aromatic in both series but show the inverse stability of the push-pull and captodative isomers, the latter being more stable by up to 10 kcal/mol (in gas).The difference between the MHlg₃ groups and conventional organic groups is that in the latter the electron density is transferred to the π-system of the substituent, while the former can accept it only to the σ*(CM) orbital. Thus, when the electron donor and acceptor effects are separated between the σ and π systems, captodative isomers can be more stable than their push-pull isomers with more extended conjugation.

The cover image is based on the Research Article Asymmetric electronic deformation in graphene molecular capacitors by S. Salehfar et al., https://doi.org/10.1002/qua.27426.

[Correction added on 25 July 2024, after first online publication: Cover has been replaced.]

In this study, we investigated the mechanism of the inactivated hexene hydrogenation reaction catalyzed by a ruthenium (II) complex containing “N-heterocyclic carbene” (NHC) ligands, specifically SIMes and CBA, using DFT calculations. Our focus was on RuH(OSO₂CF₃)(CO)(SIMes)(CBA), which exhibits excellent catalytic behavior. We tested the B3LYP-D3, cam-B3LYP, and TPSSh functionals. The hydrogenation reaction is initiated by the release of SIMes rather than CBA due to the lower associated dissociation energy. Our findings indicate a reaction mechanism consisting of two consecutive steps, each involving one hydrogen atom migration. The first step, considered as the kinetically limiting transition state, exhibits a Gibbs free activation barrier of 12.9 kcal mol⁻¹. This step involves two asynchronous processes. The first one describes the migration of the ruthenium hydride to the internal carbon of the olefine function, transitioning from π to σ coordination mode, which promotes the formation of a bond between ruthenium and the terminal olefinic carbon. The second process involves the oxidation of ruthenium from Ru(II) to Ru(IV). This oxidation is crucial as it enables the decomposition of the H₂ molecule into two hydrogen atoms bonded to the ruthenium atom. The geometrical structures of the Hidden Reaction Intermediate Ru(II) complex and the quasi-transition state of the second process have been determined by means of the RIRC technique. The second step entails the migration of one of the newly formed hydrides of the Ru(IV) complex to the terminal olefinic carbon, resulting in the release of hexane with a weak activation Gibbs free energy of .8 kcal mol⁻¹. Lastly, we explored the use of dichloromethane as a solvent, considering the PCM model. The presence of the solvent significantly decreases the energy dissociation of SIMes from 17.9 to 9.0 kcal mol⁻¹, providing notable benefits.

Multi-resonant thermally activated delayed fluorescent (MR-TADF) materials, which combine large oscillator strengths, small singlet-triplet energy gaps, high photoluminescence quantum yields, and color purity, have attracted great interest in both experimental and theoretical research in recent years. However, the differences between two classes of MR-TADF, utilizing carbonyl groups and boron atoms as acceptors respectively, have not been clearly delineated, and the implementation of strategies combining both is extremely limited. This limitation hampers the diversity in composition and structure of MR-TADF. In this study, we employed boron as the central acceptor and carbonyl groups as peripheral acceptors, designing and investigating 7 merged systems of MR-TADF molecules. Calculations revealed that, in contrast to the strong acceptor characteristics of boron atoms, carbonyl groups do not exhibit absolute acceptor features, and their resonance effects depend on the surrounding environment. This unique resonance effect induces LRCT features to varying degrees, enabling the emission coverage of these molecules across almost the entire visible spectrum (theoretical emission wavelengths covering 452–751 nm). We gained an understanding of the differences between boron acceptors and carbonyl groups, achieving full-color emission by adjusting only the MR cores. This provides insights into the rational design of complex-component full-color MR-TADF emitters.

This research has discovered relationships between atom reactivity parameters (such as electronegativity or hardness) and the pressure exerted on their electronic shells. These relationships are derived from the relationship between the radius of the atom confined within a spherical box and the pressure exerted on the box by its electrons. To determine the pressure corresponding to each radius, it was essential to formulate a set of new basis functions valid for calculating the energy of confined atoms. These new basis functions, Simplified Box Orbitals (SBOs), stem from the previously studied SBOs, but their coefficients are obtained variationally instead of being fitted to a Slater-Type Orbital (STO), and the powers (R−r)^k are selected differently. These differences make them especially suitable for treating confined atoms and distinguishing between “hard” and “soft” confinements. This methodology has proven useful for accurately calculating the properties of various atoms under different pressures, namely H, He, Li, Be, B, C, N, O, F, and Ne. Furthermore, we believe that the new basis functions are suitable for obtaining Gaussian expansions that will enable the treatment of confined molecules, which we intend to study in a subsequent work.