International Journal of Quantum Chemistry最新文献

In this work, we investigate quantum information entropy for double hyperbolic well potentials within the framework of the fractional Schrödinger equation (FSE). Specifically, we analyze the position and momentum Shannon entropies for two hyperbolic potentials, $��{�U�}_{�1�}�$ and $��{�U�}_{�2�}�$, as a function of the fractional derivative order $��\mu �$. Our findings reveal that decreasing $��\mu �$ enhances wave function localization in position space, thereby reducing spatial uncertainty while simultaneously increasing momentum uncertainty. We confirm the validity of the Beckner–Bialynicki-Birula–Mycielski inequality for both potentials, demonstrating its robustness across different degrees of nonlocality. Furthermore, we explore the behavior of Fisher information, observing that it increases in position space while decreases in momentum space as the well depths grow.

The electronic and nonlinear optical (NLO) properties of XAl₁₂-Y (X = Be, Al, C, and P; Y = K and K₃O) were systematically investigated theoretically. Density functional theory calculations demonstrated that the Y ligands bind strongly to the XAl₁₂ clusters with high binding energies. Natural population analysis revealed that an electron is transferred from (super)alkali to the XAl₁₂ cluster. XAl₁₂-Y exhibits excellent NLO response, as evidenced by the calculated static and dynamic first hyperpolarizabilities, as well as hyper-Rayleigh scattering (HRS) hyperpolarizabilities. The NLO responses critically depend on the XAl₁₂ core and ligand type, with PAl₂-K, CAl₁₂-K₃O, and PAl₁₂-K₃O showing superior performance. The remarkable NLO responses of these systems primarily arise from (super)alkali ligands, underscoring the critical role of ligand introduction in enhancing the NLO response of the system. This work demonstrates that combining potent (super)alkalis with tunable superatom acceptors is a highly effective strategy for designing high-performance NLO materials.

The trans-to-cis photoisomerization behavior of azobenzene endows them with excellent photo-switching potential, and the modulation of the conjugated system can effectively optimize their nonlinear optical (NLO) responses and switching efficiency. In this study, we systematically investigated, through density functional theory (DFT) calculations, the effects of conjugation length and the position of the NN bond on the electronic structures, excited-state properties, and NLO performances of azobenzene derivatives modified with –NH₂ and –NO₂ groups. The results indicated that extending the conjugated system significantly reduced the HOMO-LUMO energy gap. When the NN bond was near the –NO₂, the charge transfer efficiency was notably enhanced, and the static first hyperpolarizability of the trans configuration reached up to 17.54 × 10³ a.u. Additionally, the synergy between conjugation elongation and the position of the NN bond improved the photo-switching efficiency, which could be as high as 3.28 in that of the 2–2 system. Moreover, having the NN bond adjacent to the –NO₂ lowered the isomerization energy barrier, further optimizing the photo response properties. This work provides a theoretical basis for designing high efficient photo-switching materials.

Unsymmetrical xanthene dyes are a hybrid structure of two symmetrical xanthene dyes. Therefore, are the structural, spectral, electronic, linear, and non-linear optical (NLO) properties of unsymmetrical xanthene dyes comparable to, distinct from, or better than those of their parent symmetrical xanthene dyes? This study provides a detailed analysis of unsymmetrical and symmetrical xanthene dyes using the Density Functional Theory (DFT) and Time-dependent (TD)-DFT methods. DFT study demonstrated that symmetrical xanthene dyes are energetically more stable and exhibit BLA values lower than unsymmetrical xanthene dyes. Moreover, symmetrical xanthene dyes show destabilized energy of HOMO, LUMO, and lower LUMO–HOMO energy gap than unsymmetrical xanthene dyes. Vertical excitation calculated from the TD-DFT method shows reasonable agreement with experimental absorption. However, unsymmetrical xanthene dyes with higher dipole moments and hyperpolarizability show superior NLO properties.

Developing novel non-fullerene acceptors (NFAs) by modifying A₁-DA₂D-A₁ Y6 molecules is an effective strategy to improve the energy conversion efficiency of organic solar cells (OSCs). To understand the mechanism of regulating the photovoltaic performance by modifying the central fused ring, end group, and inner chain segments of Y6, D18:Y6, D18:AQx-2, D18:AQx-18, D18:BTIC-γ-2CN and D18:Z9 OSCs were systematically studied based on extensive quantum chemistry calculations, and the impacts of different chemical groups on molecular properties and photovoltaic performances were analyzed. The substitution of benzothiadiazole in the central fused ring of Y6 with quinoxaline, substituting quinoxaline with phenazine, introducing benzonitriles at the end group, and phenyl groups into inner side chains enhance molecular skeleton planarity, slightly elevate the highest occupied molecular orbital energy and the lowest excitation energy, and enlarge light absorption efficiency. Introducing quinoxaline and phenyl groups causes the reduction of the electrostatic potential difference between D18 and NFAs; on the contrary, introducing phenazine and benzonitriles induces the opposite effects. Introducing quinoxaline and phenazine generates negligible effects on charge transfer (CT) energies, whereas introducing benzonitrile and the phenyl group increases CT energies. Introducing phenazine and the phenyl group generates sufficient energy difference between local excitation and CT to conquer exciton binding. The rate constants calculated using Marcus theory indicate that all molecular modifications of Y6 reduced exciton dissociation rates. However, the introduction of benzonitrile increases CT and suppresses charge recombination rates. The results reveal the inherent relationship between molecular structure and photovoltaic performance, providing the theoretical basis for the design and development of NFAs.

Density functional theory (DFT), molecular dynamics simulations (MDS), mass loss (ML), and electrochemical studies were performed to assess the corrosion preventive ability of oxadiazole derivatives, 1-(1((5-phenyl-1,3,4-oxadiazol-2-yl)methyl)-1H-benzo[d]imidazol-2-yl)-3-(thiophene-2-yl)prop-2-en-1-one (PBTP) and 3-(furan-2-yl)-1-(1((5-phenyl-1,3,4-oxadiazol-2-yl)methyl)-1H-benzo[d]imidazol-2-yl)prop-2-en-1-one (FPBP) on N80 steel (NS) in 15% HCl medium. The compounds PBTP and FPBP exhibited corrosion preventive ability of 97.13% and 94.16% for NS in the presence of 250 ppm concentration at 298 K temperature. Corrosion inhibition efficiency of both compounds increases with increase in concentration and decreases with increase in temperature. Adsorption of both inhibitors followed Langmuir adsorption isotherm. Potentiodynamic polarization studies suggested that both inhibitors behave as mixed type (anodic as well as cathodic) inhibitors. The analysis of field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) verified the development of the inhibitor protective layer at the NS surface to prevent its corrosion. The computational studies are in good agreement with the experimental results.

Single-atom catalysts (SACs) with high activity and selectivity are regarded as excellent OER catalysts, but easily corroded under acidic environment. Here, we employed density functional theory (DFT) calculations to design a series of SACs protected by twisted bilayer graphene (tBLG) “chainmail.” Charge transfer analysis showed that the carbon layer could serve as an intermediate between transition metal atom and reactants. In addition, rotation operation on bilayer graphene was applied to further enhance the catalytic performance. Thermodynamic free energy diagrams of eight types metal atoms and five rotation angles were systematically discussed. A volcano plot of overpotentials among all the studied single metal atom twisted bilayer graphene catalysts can be described by ($��\Delta �G_{�O�*�}�-�\Delta �G_{�\mathrm{OH}�*�}�$). The designed Ni-tBLG catalyst (rotation angle is 21.8°) exhibited the best performance with the lowest OER overpotential of 0.35 V. These results revealed that the selected single metal atom twisted bilayer graphene catalysts with high activity and stability could be treated as efficient OER catalysts.

The molecular structure of phenyl-substituted cyclopropanecarboxylic acid (PSCCA, C₁₂H₁₄O₂; 3-methyl-3-phenylcyclobutane-1-carboxylic acid) was determined using nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and X-ray crystallography techniques. Following structural confirmation, its molecular geometry was optimized at the Density Functional Theory (DFT) level. The van der Waals interactions were accurately accounted for using the DFT-D3 method in the CP2K program. Understanding the adsorption behavior of organic molecules on metal surfaces is of great significance for applications in catalysis, sensor design, surface functionalization, and corrosion prevention. In this context, the adsorption properties of the PSCCA molecule on Al and Cu surfaces were investigated in detail using DFT-based CP2K calculations. By optimizing different adsorption configurations, the binding energies of the most stable structures were calculated and compared. The obtained results indicate that the PSCCA molecule strongly binds to both Al and Cu surfaces, with a higher adsorption energy on the Al surface compared to the Cu surface. In addition, Mulliken population analysis revealed distinct electronic charge transfer characteristics upon adsorption, with substantially stronger electron transfer observed on the Cu(111) surface due to enhanced d-band–ligand orbital hybridization. This electronic behavior correlates with the adsorption strength and highlights the critical role of metal electronic structure in governing surface interactions. Electron density difference analyses suggest that PSCCA interacts with both surfaces via a physisorption mechanism. Furthermore, assessments in the context of surface inhibitor efficiency reveal that PSCCA has the potential to passivate active surface regions and hinder surface reactions. Analyses conducted under different pH conditions indicate that the inhibitory effect of PSCCA is particularly pronounced in acidic environments. These findings suggest that PSCCA, exhibiting higher adsorption energy and stability on the Al surface, can be considered an effective protective agent and may play a crucial role in the design of metal–organic interfaces.