The effects of single-vacancy and double-vacancy doping with alkaline-earth metals on the stability, electronic structure, charge transfer, and optical properties of molybdenum ditelluride in the monolayer defective state (MoTe2) have been investigated using first-principles methods. It is found that the structure of the molybdenum ditelluride system is more stable after double Te vacancies, with direct band-gap to indirect band-gap transitions occurring in single Te vacancies and Mo vacancies, and semiconductor to quasi-metal transitions occurring in double Mo vacancies. The binding energy in the defect state system of molybdenum ditelluride after vacancy defects is always negative, and the structure remains stable. In this paper, the most stable double Te vacancy state was selected for substitutional doping with alkaline-earth metals, and the Be atoms were doped with the largest amount of morphology, and Ca atoms were doped with the most pronounced decrease in band gap value. The direct band-gap semiconductor is maintained after doping with Be atoms. Doping with Mg, Sr and Ba changes the band-gap from direct to indirect. The double Te defect state MoTe2 doped with Ca atoms has a tendency to transition to a quasi-metal. Regarding photoelectric properties, the system is blue-shifted on both the absorption and reflection peaks.
The understanding of noncovalent interactions is crucial in explaining critical phenomena such as self-assembly, chemical reactivity, and crystallization. This work examines the energetic diversity of conformations and local minima for several halogenated dimers, represented as R-X (R = H, F, CH3, CF3; X = Cl, Br, I). Thousands of configurations are randomly generated and refined through geometric optimizations to yield a diverse set of molecular conformers. Frequency calculations were performed for all optimized conformers to confirm that they are local minima. The noncovalent interactions in optimized dimers of halogen-containing molecules were analyzed with atom in molecules (AIM) method and symmetry-adapted perturbation theory (SAPT). Additionally, a protocol for generating machine learning models to recover accurate predictions of the physically meaningful SAPT energy components with minor computational cost is presented. These results deepen our understanding of the intricate energy balance and dedicated equilibrium of different noncovalent interactions in halogenated dimers.
Boron, the element which is in close proximity with carbon in the periodic table has been hypothesized to produce diverse two-dimensional structures that differ from well-studied 2D materials. Icosahedron , the monomers of which form the crystalline boron structure, appears as a recurring pattern in the chemistry of boron compounds, elemental boron and boron-rich materials, functions as a building block in a majority of boron allotropes. The topological study of the icosahedral sheets is a necessary field to be investigated for the effective analysis and characterization of its physico-chemical attributes without undertaking time-consuming experimental research. The topological descriptors being expressed as numerical values enable scientists to compare and correlate data, which can be applied to quantitative structure-activity relationships and quantitative structure-property relationships modeling. In this study, various degree based molecular descriptors of the crystal boron icosahedral sheet has been formulated from a two-dimensional lattice perspective using the -polynomial approach. To establish the significance of these descriptors in the study of chemical attributes, an efficient linear regression modeling has also been performed, enabling the prediction of properties of several other boron sheets.
This article presents an educational overview of the latest mathematical developments in coupled cluster (CC) theory, beginning with Schneider's seminal work from 2009 that introduced the first local analysis of CC theory. We provide a tutorial review of second quantization and the CC ansatz, laying the groundwork for understanding the mathematical basis of the theory. This is followed by a detailed exploration of the most recent mathematical advancements in CC theory. Our review starts with an in-depth look at the local analysis pioneered by Schneider which has since been applied to various CC methods. We subsequently discuss the graph-based framework for CC methods developed by Csirik and Laestadius. This framework provides a comprehensive platform for comparing different CC methods, including multireference approaches. Next, we delve into the latest numerical analysis results analyzing the single reference CC method developed by Hassan, Maday, and Wang. This very general approach is based on the invertibility of the CC function's Fréchet derivative. We conclude the article with a discussion on the recent incorporation of algebraic geometry into CC theory, highlighting how this novel and fundamentally different mathematical perspective has furthered our understanding and provides exciting pathways to new computational approaches.
Multiple proton transfers in cyclic homogenous and mixed H2O-H2S clusters from trimers to pentamers have been investigated at an affordable and accurate level of theory. Reaction force and Wiberg bond index analyses showed the process to be nearly synchronous in all the homogenous clusters, while asynchronous in the mixed clusters; always initiated by movement of the SH protons to the H-bonded O atoms. The barriers for proton transfers exhibited a complex pattern, decreasing initially from the homogeneous H2O cluster upon replacement of one H2O by an H2S moiety and subsequently rising monotonically with each subsequent replacement(s) to becoming highest in pure H2S clusters. Finally, the impact of the energetic and mechanistic modulations on the proton transfer kinetics has been studied.
The Schrödinger equation for the hydrogen atom enclosed by an impenetrable spherical cavity is solved through a Finite-Differences approach to gain an insight on the actual nature and structure of the ansatz wavefunction cutoff factor widely used in an ad hoc manner in corresponding variational calculations to comply with the Dirichlet boundary conditions. The results of this work provide a theoretical foundation for the choice of the appropriate analytical cutoff functions that fulfill the boundary conditions. We find three different regions for the behavior of the cutoff functions. Small cavity radius where the cutoff function has a parabolic behavior, an intermediate region where the cutoff function is quasi-linear, and a large cavity region where the cutoff function is a step-like function. We deduce the traditional linear and quadratic cutoff functions used in the literature as well as its validity region for the confining radius. Finally, we provide a mathematical deduction of the exact cutoff function in terms of the nodal structure of the free hydrogenic wavefunctions and a relation to the Laguerre polynomials for some cavity radii where the free atomic energy level coincides with a confined energy level. We find that the cutoff function transit over several unconfined solutions in terms of its nodal structure as the system is compressed.
In this work, theoretical calculations of o-phenylphenol-based non-oxovanadium(IV) and organotin(IV) complexes, previously prepared and reported by our group, have been carried out by density functional theory (DFT). Density functional theory quantum chemical computations were used to explore the structural and spectroscopic characteristics of the complexes in this study. The inhibitory nature of complexes were revealed via molecular docking research, which were performed against selected breast cancer cell proteins, 5NWH and 3HB5. The optimization and stability of complexes 1–6, were conducted using optimized DFT/B3LYP/6–311++G (d, p) level. Simulated computations of the molecular electrostatic potential surface were also performed to analyze the reactive behavior of the non-oxovanadium(IV) and organotin(IV) complexes. The stability and molecular reactivity of the molecules were computed using the HOMO-LUMO energies, energy gap, chemical potential (μ), electronegativity (χ), hardness (η), and softness (S) values. In silico analysis through molecular docking, ADMET properties and toxicity evaluation was used to assess its anticancer activity, drug-likeness property and toxicity. The binding constant value, evaluated from molecular docking, was found to be very promising, −10.1 kcal mol−1 observed for vanadium complex 5 and the complexes were found to exhibit inhibition constant as low as 0.0378 μMol. Root-mean-square deviation (RMSD) has been carried out to validate molecular docking studies, which have been found to be below 2.0 Å for the complexes, indicating successful docking of the ligand-protein complex by the program. The complexes, evaluated for their toxicity behavior in terms of Lethal Dose, based on Globally Harmonized System (GHS), have been found to be chemical safe falling under the category III and V and hence can find use as future metallo-based drugs.
Using density functional theory, we investigated the adsorption of different gases, including CO, CO2, H2S, NO2, and SO2, on decorated phosphorene with various alkali metals such as Li, Na, K, Rb, and Cs. Gas molecules are physisorbed on phosphorene and, according to calculations, alkali metal decoration significantly improves the adsorption of gas molecules by phosphorene due to the reinforcement of interface interactions. Based on the stability criterion (ΔEads), the preference for choosing the best decorated phosphorene system for adsorbing different gases can be arranged as follows: Li > Na > K > Rb > Cs. Li-phosphorene is the most stable decorated system, and due to its higher binding energy in complexation with CO, CO2, H2S, NO2, and SO2, Li-decorated phosphorene shows greater potential in absorbing these gases. Donor-acceptor interactions analysis has confirmed that the origin of stability can be attributed to molecular orbital interactions between these metals and the phosphorene surface (201.69 kcal mol-1). Based on the calculated adsorption energies, Li-decoration on black phosphorene has the most significant adsorption value for CO (−2.48 eV). Finally, Li has been suggested as the most suitable phosphorene decorator for enhanced gas molecule adsorption or detection.
The efficacy of aniline and carbazole-based sensitizers used in dye-sensitized solar cells (DSSCs) is correlated with the trends in density functional theory (DFT) based charge transfer (CT) and non-linear optical (NLO) properties since both DSSC and NLO properties highly rely on CT properties. The aniline-based donors showed a higher degree of planarity over carbazole-based donor sensitizers. This improved planarity in aniline-based sensitizers is attributed to efficient charge transfer and higher dipole moment. The efficient CT within the sensitizers is confirmed with bond-length alternation (BLA), bond order alternation (BOA), and quinoid character (QC). A direct correlation of band-gap (EG) with μ, ω, η, and Γ is witnessed. Time-dependent DFT (TD-DFT) results of vertical excitation demonstrated similar trends that are observed practically. Indeed, we observed a direct correlation between α and β and the experimentally observed DSSC efficiency. DFT and TD-DFT methods, linear, employed for computing the CT and linear and DSSC properties as implemented in Gaussian 09. NLO properties were simulated through single-point polar calculations. B3LYP and PBE1PBE functionals were used for geometry optimization. The linear and NLO properties were determined in various functionals, that is, global hybrid and range-separated hybrid functionals. A polarizable continuum model (PCM) was used for solvation studies. To understand the realistic picture of the dye@TiO2 cluster, dye bound on TiO2 clusters were optimized using a LANL2DZ basis set specifically for the Ti atom.
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