Theoretical Chemistry Accounts最新文献

The detailed analysis of the mechanism of metathesis of N-methylformamide with dimethyl carbonate leading to the formation of N, O-dimethylcarbamate was carried out using the B3LYP/6-311++G(df,p), B3LYP-D3(BJ)/6-311++G(df,p) and ωB97XD/6-311++G(df,p) density functional methods. The reactions proceed in three stages. The first step consists in the tautomeric conversion of N-methylformamide to iminol. The second stage, which is the rate-limiting step, involves the addition of dimethyl carbonate via the N=C π-bond of iminol. The third stage of the reaction is the cleavage of the methyl formate molecule from N-methyl-N-[(hydroxy)(methoxy)methyl]-O-methylcarbamate. This conversion results in the formation of N, O-dimethylcarbamate. All stages of the reactions are catalyzed by associates of alcohols, which lead to a strong decrease in activation enthalpies.

In this paper, we investigate two model reactions (an electrocyclic ring closure and a tautomerism equilibrium) in different sized fullerene cages to explore the intricate details of the confinement effect in chemistry and in chemical reactivity. Fullerene cages offers, with their unique geometry and electronic properties, an ideal theoretical model to explore confinement-induced alterations in reaction pathways and energy barriers. Computational results demonstrate that the induced confinement may significantly influence the thermodynamics and kinetics of the chemical processes under study through a comparative investigation of reactions in various fullerene cage sizes and their occurrence in gas phase. This theoretical investigation intends to improve our knowledge of molecular confinement events, while also highlighting the potential use of fullerene cages as adjustable nanoreactors for regulating and improving chemical reactivity.

Machine learning (ML) approaches have been developed to predict materials’ corrosion inhibition efficiency, particularly pyrimidine compounds. Notably, the virtual sample generation (VSG) technique enhances prediction accuracy, a novel approach for handling small datasets in this context. The random forest model, the best-performing nonlinear algorithm, showed substantial accuracy improvement based on the increase in R² value from 0.05 to 0.99 and the decrease in RMSE value from 5.60 to 0.42, after applying VSG. These results underscore the efficacy of the VSG technique in boosting the predictive performance of ML models, particularly in scenarios constrained by limited data availability.

Based on the first-principles calculations, we systematically studied and fully characterized the electronic structure and optical properties of four novel ZnO phases assembled by Zn₁₂O₁₂ clusters and compared them with the results of wurtzite (WZ) ZnO. The results show that the density of states of the four cluster-assembled materials is similar to that of WZ-ZnO, but the bandgap is larger than that of the latter. Among them, FAU-ZnO, LTA-ZnO, and SOD-ZnO are direct bandgap semiconductors. The calculation of the optical properties of SOD-ZnO is most similar to those of WZ-ZnO, but R-ZnO has higher static permittivity, reflection, and refraction coefficients. Considering that the presence of cage-like voids in cluster-assembled materials is more conducive to doping of various elements, cluster-assembled materials are more likely to change the bandgap and corresponding electronic structure through doping than WZ-ZnO. From this perspective, these two materials have great potential for photocatalytic and optoelectronic device applications.

A computational study on the host–guest complexes of neutral bis(4-nitrophenyl)squaramide (SQ) and halide anions is reported. In the gas-phase, the calculated interaction and stabilization energies indicates a diminishing intrinsic affinity of SQ for anions from fluoride to iodide. The nature of interactions is investigated using Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM) along with Energy Decomposition Analysis-Natural Orbitals for Chemical Valence (EDA-NOCV). While electrostatic interactions account for roughly 60% of the total, EDA-NOCV analysis demonstrated increasing contributions of orbital interactions from (left[ {{text{SQ}} cdots {text{I}}} right]^{ - }) to (left[ {{text{SQ}} cdots {text{F}}} right]^{ - }) complexes. In solution, thermodynamic cycle analyses and Gibbs free energy calculations reveal a propensity towards the formation of (left[ {{text{SQ}} cdots {text{F}}} right]^{ - }), taking into account the influence of solvation energies on the overall stability. The consistent trend observed in selectivity both in the gas phase and in solution suggests that changes in solvation energy do not significantly impact the stability of complexes. The findings were additionally supported by a significant correlation observed between the computed and experimental formation constants.

Efficient calculations of the quantum product state-resolved differential cross sections play a crucial role in unraveling the dynamics of a chemical reaction. Using hyperspherical coordinates, a stair-shaped grid-based time-dependent quantum wave packet method is proposed for efficiently calculating the product quantum state-resolved reactive scattering information. As numerical examples, quantum product state-resolved reaction probabilities for the reactions of O + O(_{2}) and Cl + H(_{2})((v_0)=1) with (J=0) are computed, which involve long-time resonance states extending over long-range grids and are difficult for obtaining accurate results using the time-dependent method. The results through calculations are being compared to those obtained using the reactant coordinate-based (RCB) method and the interaction-asymptotic decomposition method (IARD).

Quantum dots (QDs) have attracted significant interest because of their tunable bandgaps, which enable numerous applications in fields such as photovoltaics, biomedicine, and materials science. This study explores various core electron treatments in the density functional theory (DFT) analysis of II-VI semiconductor quantum dots and their bulk counterparts. We compared All-electron (AE), Effective Core Potential (ECP), All-Electron Relativistic (AER), and DFT-Semicore pseudopotential (DSPP) treatments. Our findings indicate that the AE treatment aligns closely with the experimental results for smaller QDs, whereas the accuracy of DSPP increases with larger QDs. DSPP provides an optimal balance between computational efficiency and accuracy, making it suitable for studying II-VI QDs. Notably, the bandgap behavior varies, being direct for zinc and cadmium chalcogenides, whereas mercury chalcogenides are zero-gap semiconductors (semimetals). The inner bonds of the QDs exhibit an ionic character, whereas the terminal bonds display a covalent character. This study enhances our understanding of the structural and electronic properties of II-VI quantum QDs, aiding their application in various technologies.

In this study, the geometric and electronic properties of Ti2CO2 and Ti2CO2/G heterostructures as anode materials for sodium-ion batteries were systematically investigated using first-principles calculations. The storage mechanism and properties of sodium atoms on Ti₂CO₂ and Ti₂CO₂/G heterostructures were further studied. By comparing the adsorption energy (− 1.4 eV, − 1.26 eV), diffusion barrier (0.21 eV, 0.14 eV), storage capacity (478mAh/g, 528mAh/g), average open-circuit voltage (0.68 eV, 0.51 eV), and elastic modulus (161.40 N/m, 364.82 N/m) of sodium atoms on Ti₂CO₂ and Ti₂CO₂/G heterostructures, we found that Ti₂CO₂/G heterostructure exhibits superior structural stability, better electronic conductivity, higher storage capacity, lower average open-circuit voltage, lower diffusion barrier, and superior mechanical performance. Through this study, we explore the potential of Ti₂CO₂/G as an anode material for sodium-ion batteries and its sodium storage mechanism.

The selectivity of the sodium channel has been the subject of numerous experimental and theoretical studies. In this work, this problem is approached from a theoretical point of view based on a model built from the Selective Filter (SF) of the open structure of the voltage-activated channel of the bacterium Magnetococcus marinus. This approach has allowed us to calculate the interaction energies of the system (cation-water-SF-fragment), both for the sodium cation and the potassium cation. The results have highlighted the importance of differential dehydration of cations, as well as the environment where it occurs. Semi-empirical and ab initio methods have been applied to analyze and quantify the interaction energies when the cations are in the SF of the sodium channel, with the DFT (ab initio) methods giving us the key to the distribution of the interaction energies and therefore how dehydration occurs.

It is well-known that the Spin-Coupled (SC) description of the cyclopentadienyl anion is problematic. A converged six electrons in six orbitals SC calculation on this anion break the D_5h electron density spatial symmetry by approximately localizing two of the six pi singly-occupied orbitals over one carbon. A complete active space valence bond (CASVB) calculation for the same six pi electrons in six orbitals does not break symmetry, yielding five equivalent pi orbitals over the five carbons and one pi orbital with high amplitude along the C₅ molecular rotation axis. A Spin-Coupled calculation comprising six electrons in five orbitals, SC(6,5), yields five equivalent non-orthogonal pi orbitals over the carbons with “1.2” (6/5) electron occupancy each. In this paper, these different solutions are contrasted with one generated by the present author in which five spatially different but equivalent configurations of a perfect-pairing symmetry broken solution are put together in a multi-configuration Spin-Coupled calculation of six electrons in 30 orbitals. It is concluded that, in spite of the computational complexity of this calculation, its result is qualitatively more akin to a valence bond-like description of the resonant pi system of the cyclopentadienyl anion.