International Journal of Quantum Chemistry最新文献

Quantum dots have many potential applications in opto-electronics, energy storage, catalysis, and medical diagnostics, silicon carbide quantum dots could be very attractive for many biological and technological applications due to their chemical inertness and biocompatibility, however, there are seldom theoretical studies that could boost the development of these applications. In this work, the electronic properties of hydrogenated spherical-like SiC quantum dots with C-rich and Si-rich compositions are investigated using density functional theory calculations. The quantum dots are modeled by removing atoms outside a sphere from an otherwise perfect SiC crystal, the surface dangling bonds are passivated with H atoms. Our results exhibit that the electronic properties of the SiC-QD are strongly influenced by their composition and diameter size. The energy gap is always higher than that of the crystalline SiC, making these SiC QD's suitable for applications at harsh temperatures. The density of states and the energy levels show that the Si-rich quantum dots had a higher density of states near the conduction band minimum, which indicates better conductivity. These results could be used to tune the electronicproperties of SiC quantum dots for optoelectronic applications.

Pyrene-based molecules are being explored as prospective fullerene-free acceptors for organic solar cells (OSCs), due to their easy accessibility, structural planarity, and excellent electron delocalization. In this work, we successfully designed and analyzed pyrene-based acceptor materials (QL1–QL8) to investigate their photophysical and electro-optical parameters. Various geometric parameters were computed at the MPW1PW91/6-31G(d,p). Advanced quantum chemical approaches were employed to characterize the molecules. All the tailored molecules (QL1–QL8) exhibit a lower bandgap than the reference (R), signifying their superiority. Among these, QL8 was found to have a maximum absorption (λ_max) at 791.37 nm and an optical bandgap (E_LUMO − E_HOMO) minimum of 2.11 eV. Redshifted absorption spectra are observed in both gaseous and solvent phases for all the designed (QL1–QL8) molecules in contrast to R. Among these, QL4 exhibits the highest light harvesting efficiency (0.9826), and open-circuit voltage. A detailed donor–acceptor investigation of QL8/PBDB-T revealed the marvelous charge switching at the donor–acceptor interface. The approach used in this study is anticipated to facilitate the manufacturing of highly efficient OSC molecules.

In this manuscript, structural, electronic, magnetic, and thermoelectric aspects of AFeO₃ (A = Ca, Sr, Ba) have been calculated by means of the Full-Potential Linearized Augmented Plane Wave Method (FP-LAPW) using spin-polarized Density Functional Theory (DFT). The calculated structural parameters have been found to be in good resemblance with previously available work. Enthalpy of formation and cohesive energy along with tolerance factor confirms structural stability. Electronic properties by Trans Blaha modified Becke–Johnson potential (TB-mBJ) suggest metallic behavior in the spin-up channel and semi-conducting behavior in the spin-down channel that supports half-metallic behavior with mixed covalent and ionic bonding. Density of States (DOS) analysis confirms the major contribution of Fe-3d-states in the conduction band and O-2p states in the valence band. The half-metallic nature is further confirmed by the integer value of the total magnetic moment. The real and imaginary parts of dielectric functions, optical conductivities, absorption coefficients, reflectivity, and energy loss function have been calculated to evaluate suitability for optical applications. Thermoelectric properties with temperature range 300–900 K against chemical potential including figure of merit, Seebeck coefficient, thermal conductivities, and power factor, were examined using BoltzTraP code. Findings suggest that AFeO₃ (A = Ca, Sr, Ba) compounds suitable for spintronic, thermoelectric as well as energy harvesting applications.

This manuscript presents, under the effect of different pressures (0–60 GPa), the structural, mechanical, electronic, optical, and thermoelectric properties of CdO with NaCl type structure by using the FP-LAPW (Full Potential Linearized Augmented Plane Wave method) with Generalized Gradient Approximation (GGA) whose basis is the Density Functional Theory (DFT). PBE-GGA was used to compute the structural, elastic, optical, electronic, and thermoelectric properties using Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. Different terms like formation energy, cohesive energy, and phonon were used for the computation of thermal stability and that is further confirmed by elastic properties. Bulk moduli and pressure-dependent lattice constants were achieved by using the optimization method. From the results, we can say that the increase in pressure is directly related to the band gap and inversely related to the lattice constant. The mechanical properties show that CdO is highly ductile and mechanically stable and ductility is directly related to pressure. The minimum conduction band goes to a higher energy level when the pressure increases while the maximum valance band goes to a lower energy level ultimately the energy band gap increases. The optical parameter curve does not change by increasing pressure but the peaks start moving towards the higher energies slightly. Calculations reveals that band gap increases by increasing pressure which shows the blue shift in optical properties. The optical properties spectrum was studied, including reflectance, dielectric coefficient, and absorption coefficient. The optical constants show that the phase of CdO with NaCl structure was translucent. In the end, the thermoelectric feature in terms of thermal conductivity (K), power factor (PF), Seebeck coefficient (S), and electrical conductivity (σ) were studied by using the BoltzTrap code as a function of temperature. Thermoelectric and optical aspects revealed that pressure induces the possible use of CdO material for various TE and optical applications.

Quasiparticle self-consistent many-body perturbation theory (MBPT) methods that update both eigenvalues and eigenvectors can calculate the excited-state properties of molecular systems without depending on the choice of starting points. However, those methods are computationally intensive even on modern multi-core central processing units (CPUs) and thus typically limited to small systems. Many-core accelerators such as graphics processing units (GPUs) may be able to boost the performance of those methods without losing accuracy, making starting-point-independent MBPT methods applicable to large systems. Here, we GPU accelerate MOLGW, a Gaussian-based MBPT code for molecules, with open accelerators (OpenACC) and achieve speedups of up to $��9�.�7�\times �$ over 32 open multi-processing (OpenMP) CPU threads.

Combining FDA-approved medications may increase biological activity by simultaneously targeting many protein mechanisms while being less toxic. Gemcitabine and docetaxel together might have a synergistic impact that kills cancer cells and makes them more effective against breast cancer. This study used the foundation set B3LYP/6–311 G to optimize the gemcitabine with the docetaxel structure that was created. Theoretical calculations were made for the ultraviolet to visible spectrum were studied in gas and liquid phase. The structural stability and reactivity of the combined structure were studied using the energy gap between HOMO and LUMO, and the computed energy gap (ΔE) was 4.219 eV. The electrostatic potential of complex structure was determined and the Mulliken charge population was evaluated. Through RDG analysis weak interactions of GEDT was evaluated and topology properties were studied through ELF and LOL analysis. Breast cancer target proteins were utilized in the molecular docking studies. The docking scores revealed a greater binding affinity for the complex molecule, confirming a superior combinatorial interaction between gemcitabine and docetaxel. Highest binding ability of the GEDT was against Caspase-6 and the network analysis of Caspase-6 was assessed through graph theory model. The stability of GEDT with Caspase-6 was studied through molecular dynamic simulation for 100 ns. The adsorption, distribution, metabolism, excretion, and toxicity characteristics of the complex structure were investigated, and the findings revealed the complex lead compound's safety profile and its potential for use as a potent anticancer medication.

The substitution of heteroatoms and the expansion of π-conjugated units have significant effects on the photoelectric properties of polycyclic aromatic hydrocarbons (PAHs). In this study, based on the experimental molecule PBC, 10 acene derivatives containing the pyrrole group were designed by three strategies: (1) changing the connection position of the pyrrole group, (2) exchanging the position of the N atom, and (3) increasing the length of the π-linker. Density functional theory (DFT) was used to optimize the molecular geometric structure. Time-dependent density functional theory (TD-DFT) was used to calculate the relevant parameters of the excited states. The results show that both of the pyrrole group and the N atom in the para-position, and the addition of the π-linker can reduce the energy gap, cause redshift of the linear absorption peak, and increase the two photon absorption (TPA) cross-section. The analyses of the charge density difference (CDD) and the charge-transfer matrix (CTM) proved that the electron transfer is mainly concentrated in the π-linker. Moreover, the participation of the multi-ring skeleton on both sides decreases gradually with the increase of the length of the π-linker. The length of the π-linker changes the dominant transition channel and intramolecular charge-transfer (ICT) characteristics of TPA, thus affecting the transition dipole moments and nonlinear absorption properties. The second hyperpolarizability of the designed molecule PBI5-p5 is also significantly superior to that of similar materials reported. It is expected that the above molecular design strategies and comprehensive analysis of nonlinear optical (NLO) properties could provide theoretical support for the research on acene derivatives.

The structures and properties of seven substituted dithiophosphate (DTP) collectors containing three types of functional groups (O₂PS₂, C₂PS₂, and N₂PS₂) were studied using density functional theory. The collectors studied were dibutyl dithiophosphate (DNBDTP), diisobutyl dithiophosphate (DIBDTP), dibutoxyethyl dithiophosphate (DBOEDTP), xylenol dithiophosphate (DMPDTP), diisobutyl dithiohypophosphite (3418A), diphenylamine dithiophosphate (DTADTP), and dicyclohexylamine dithiophosphate (DCADTP). The structural analysis showed that the PS bond lengths in the C₂PS₂ and N₂PS₂ types are longer than those in the O₂PS₂ type, indicating that the strength of the PS bond is weaker in the former two. The frontier molecular orbital studies showed that the energy differences between the highest occupied molecular orbitals (HOMO) of 3418A (C₂PS₂ type) and DCADTP (N₂PS₂ type) and the lowest unoccupied molecular orbital (LUMO) of galena are significantly lower than those of the other collectors, suggesting that C₂PS₂ type and N₂PS₂ type with cyclohexane could enhance the interaction with galena. Using the Fukui function to calculate the nucleophilicity and electrophilicity of the sulfur atom indicated that the S atom exhibits nucleophilicity, especially in DMPDTP and DTADTP, which contain benzene rings, and the S atom exhibits strong nucleophilicity without electrophilicity. However, due to the lack of contribution from S atoms to the LUMO orbitals, the S atoms in these two compounds are not participate in any LUMO reactions. The adsorption results demonstrated that 3418A (C₂PS₂ type) and DCADTP (N₂PS₂ type) exhibit the strongest adsorption on Pb²⁺ ions, while DMPDTP (C₂PS₂ type) and DTADTP (O₂PS₂ type) which contain benzene rings, as well as DBOEDTP (C₂PS₂ type) which does not contain a benzene ring, exhibit weaker interaction compared to the other compounds. These are consistent with the results of the frontier molecular orbital and electrophilic nucleophilicity calculations.

In this article, we study the helium atom confined in a spherical impenetrable cavity by using informational measures. We use the Ritz variational method to obtain the energies and wave functions of the confined helium atom as a function of the cavity radius $��{�r�}_{�0�}�$. As trial wave functions we use one uncorrelated function and five explicitly correlated basis sets in Hylleraas coordinates with different degrees of electronic correlation. We computed the Shannon entropy, Fisher information, Kullback–Leibler entropy, Tsallis entropy, disequilibrium and Fisher–Shannon complexity, as a function of $��{�r�}_{�0�}�$. We found that these entropic measures are sensitive to electronic correlation and can be used to measure it. As expected these entropic measures are less sensitive to electron correlation in the strong confinement regime ( a.u.).

We theoretically investigated the photothermally and optomechanically induced transparency (PTIT and OMIT) in an optomechanical system filled with quantum dots (QDs). In our proposed system, the right mechanical resonator couples with the optical cavity via radiation pressure, and the left mechanical resonator couples with the optical cavity through the photothermal effects. The system is driven by a strong pump field and a weak probe field. It is shown that double transparency windows can be observed due to PTIT and OMIT. When considering the Jaynes-Cummings coupling between the QDs and the optical cavity, three transparency windows are observed. We also show that the PTIT can be adjusted by the OMIT and the QDs in the optical cavity. What is more, the coupling strength and the frequency detuning can be used effectively to change the system absorption and dispersion in the PITT transparency window. This indicates that the group delay of the probe light can also be manipulated by the system parameters. The obtained results may be applied in the optical communication such as optical buffer, and so forth.