International Journal of Quantum Chemistry最新文献

The spectral-luminescence properties and photochemical conversions of phenol were analyzed for an isolated molecule as well as in water solvents in a continuum implicit model and explicit atomistic surroundings. This involved employing cut-edge hybrid quantum-classical methodologies to generate static optical spectra and the excited dissipative crossing potential energy curves. A combination of electronic excitations, gradient calculations, and embedding electrostatic potential fitting charges on quantum-classical molecular dynamic propagation trajectories provided statistically averaged absorption spectra. The mixed-reference spin-flip multiconfigurational linear response method based on reference triplet preprocessed in the time-dependent density-functional theory was utilized to determine conical intersections between the lowest excited and ground states, as well as two-stage transitions from the second excitation to the ground state. Non-adiabatic quantum-classical molecular dynamics defined photodissipative trajectories of excited states, their lifetimes, and crossing points through trajectory surface hopping together with the mixed-reference spin-flip and embedding electrostatic potential fitting approaches. Dyson orbitals of the extended Koopmans' theorem were applied to reveal the nature of molecular states at conical intersections and key points on photodynamic trajectories. Potential hydroxyl group cleavage predicted with conical intersections searching turns to “swift” OH deprotonation through |π→$��{\sigma }_{\mathrm{OH}}^{*}�$⟩ transition along photodynamic propagations in contrast with “long” processes leading to benzene ring deformation with stable OH bond.

The CaTiO₃ has been extensively investigated as a highly promising optical material mostly for its optoelectronic properties and its function as a host for transition metals doped in the CaTiO₃. Electronic and optical properties of CaTi_1−xCu_xO₃ (2-D and 3-D) have been thoroughly analyzed using first-principles calculations based on Density Functional Theory (DFT). The calculations of these properties in both 2-D and 3-D configurations have performed by the use of generalized gradient approximation plus Hubbard (GGA + U). The electronic characteristics including the electronic band structure, partial density of states, and total density of states have been meticulously computed for CaTi_1−xCu_xO₃ in both 2-D and 3-D. Upon analyzing the obtained results, we investigated that conduction and valence bands overlapped for both 2-D and 3-D structures revealing the metallic nature. We observed transitions mainly attributed to Cu-d, Ti-d, Ti-p, and O-p orbitals in both 2-D and 3-D configurations. Discussion delves into the significance of electronic band structure calculations in understanding optical properties. Peaks in the energy loss function are observed at 13 eV in both cases referred to the plasmon energy. Static values of the dielectric functions, extinction coefficient, reflectivity, and refraction are also computed. Our obtained results showed that the CaTi_1−xCu_xO₃ compound in 3-D form is more apt for optoelectronic devices and UV-LED applications.

SCAN/molecular mechanics molecular dynamics (SCAN/MM MD) simulations have been employed to investigate the structural and dynamical properties of La³⁺ in aqueous solution. These simulations revealed the presence of two distinct hydration shells, with the first shell exhibiting a La-O bond distance of 2.56 Å. The water molecules in this initial hydration shell displayed a mean residence time (MRT) of 208 ps, suggesting a less rigid structure. Five successful ligand exchange events occurred within a simulation duration of 100 ps. The stretching frequency of La-O was found to be 331 cm⁻¹, with a force constant of 92 N/m. Notably, the data obtained from the SCAN/MM MD simulation demonstrated good agreement with experimental findings.

The adsorption properties of ionic liquids containing pyrrolidinium cations and various inorganic anions as electrolytes on a platinum surface were analyzed using first principle density functional theory. Three different orientations of the alkyl cation chain were observed during the adsorption process. The strength and structural stability varied between non-fluorinated and fluorinated anions upon adsorption, with oxygen atoms influencing the mechanism of adsorption and driving the structural stability of the anion, while fluorine atoms played a role in determining the orientation of the cation during adsorption. Net atomic charges analysis, electron density difference methods, and electron density accumulation for this complex system were utilized to further investigate these phenomena. The results of this study provide valuable insights into the role of anions in the adsorption behavior of pyrrolidinium-based ionic liquids on platinum surfaces, shedding light on the factors that influence their adsorption properties and structural stability on a molecular level. The findings of this study contribute to a better understanding of the interplay between anions and platinum surfaces in the adsorption of pyrrolidinium based ionic liquids, which can have implications for various applications such as electrochemistry, catalysis, and energy storage.

Co-delivering FDA-approved drugs can be less harmful and boost biological activity by targeting different protein mechanism at same time. Gemcitabine and 5-Fluorouracil (GE5F) adduct work together to destroy cancer cells and increase the efficacy in the fight against breast cancer. The basis set B3LYP/6-311 G was utilized in this investigation to improve the structure of GE5F adduct. The natural bond analysis exhibited the intermolecular interactions of the GE5F adduct. Electronic transitions were seen to be π → π*, and theoretical calculations were performed for the ultraviolet to visible spectrum. The energy gap between HOMO and LUMO was used to study the GE5F adduct's structural stability and reactivity; the computed energy gap (ΔE) was 3.912 eV. The Mulliken charge population was assessed and the complex structure's electrostatic potential was established. Weak interactions of the GE5F were assessed using RDG analysis, and topological aspects were investigated using LOL and ELF analysis. Investigating the GE5F adduct's adsorption, distribution, metabolism, excretion, and toxicity properties, the results confirmed that GE5F adduct comes under the safety parameters being a drug-likeness molecule. Molecular docking experiments were conducted using target proteins for breast cancer. The complex molecule had a higher binding affinity as indicated by the docking scores, which validated the better combinatorial interaction between gemcitabine and 5-Fluorouracil. With − 9.4 kcal/mol, the complex molecule's strongest binding capacity was against PARP protein, and stable confirmation was observed through molecular dynamic simulation for 100 ns with four hydrogen bond interactions. These in silico finding will pave a way for in vitro and in vivo experiments with better enhancement of FDA approved drugs.

The current investigation employs first-principles DFT (density functional theory) calculations to examine the influence of transition metal replacements on the structural, thermodynamic, and thermoelectric properties of Cu-based chalcogenides TMCu₃Se₄ (TM = Nb/Ta/V). The PBE-generalized gradient approximation (GGA) model is utilized to compute the fundamental properties of Cu-based chalcogenides under study. A thorough examination of the energy band structures indicates that these chalcogenides are semiconductor compounds with indirect energy bandgaps. We can infer from the calculated energy band structures that the bandgap values are 1.67, 1.77, and 1.05 eV for NbCu₃Se₄, TaCu₃Se₄, and VCu₃Se₄, respectively. The $��{\mathrm{ZT}}_e�$ values for NbCu₃Se₄, TaCu₃Se₄, and VCu₃Se₄ are 0.661, 0.998, and 0.996, respectively. These values make them highly appropriate for usage in thermoelectric (TE) devices. The thermoelectric characteristics of pyrochlore oxides TMCu₃Se₄ (TM = Nb/Ta/V) suggest that these materials have promising potential for energy-related applications. The analyzed thermodynamic properties demonstrate that the Cu0based chalcogenide materials TMCu₃Se₄ (TM = Nb/Ta/V) exhibit a notable level of thermal stability.

Cluster formation has significant implications in atmospheric science and environmental chemistry. These clusters are characterized by complex interactions between their constituents, which influence their structure, stability, and growth. Experimental investigations are difficult for the initial stages of prenucleation cluster formation, which leads to larger aerosols. To understand the formation of clusters, the interactions between sea salts (NaCl, KCl, and MgCl₂), water, and sulfuric acid molecules have been investigated. Each step has been comprehensively examined and thermodynamic parameters have been computed using DLPNO-CCSD(T)/CBS//M06-2X/6-311++G(3df,3pd) to find the stabilities of the molecular complexes. Among all complexes, the binding energies of cluster (SS)₁(W)₁(SA)₃ are found to be the lowest due to the formation of HCl, hydrogen bonding, and weak van der Waal forces. Sea salts have shown a more favorable interaction with H₂SO₄ compared to H₂O molecules. The addition of H₂SO₄ increases the reactivity of the cluster (SS)₁(W)_n, while the addition of H₂O molecules reduces the reactivity of the cluster (SS)₁(SA)_n. However, further addition of H₂SO₄ or H₂O to the existing cluster (SS)₁(W)_n(SA)_n increases the free energy of formation. Furthermore, the influence of temperature was also investigated, suggesting that complex formation is slightly more favorable at lower temperatures than at higher temperatures. The negative values of thermodynamic parameters indicate, that these complexes are spontaneous and exothermic over the colder regions.

In this work, we have studied the torquoselectivity of a set of unusual ring-opening electrocyclic reactions that have not been successfully rationalized using models based on orbital symmetry nor have they been explained by steric hindrance. Firstly, the corresponding transition states have been obtained, and it has been verified that the intrinsic reaction coordinates associated with these transition states are consistent with the reactants and products of the reactions studied. This has allowed us to theoretically calculate the reaction barriers (with their corresponding thermal corrections) and compare them with the corresponding experimental values. In a second step, we have analyzed the electronic bonding structure using the methodologies of Natural Bond Orbital Analysis and Quantum Theory of Atoms in Molecules, searching for interactions that may significantly stabilize the transition states. Finally, we have analyzed the reactivity using a recent model that has allowed us to calculate the corresponding bond reactivity descriptors.