International Journal of Quantum Chemistry最新文献

Cavity optomechanics explores the interaction between light and mechanical systems through radiation pressure. This interdisciplinary field merges principles from quantum mechanics and quantum optics provides powerful tools for generating and controlling quantum states. In this research, we theoretically investigated a four-level N-atomic system within the context of optomechanics. The oscillating mirror possesses a mass that varies with position and exhibits a singularity. We analyzed the dynamics using Heisenberg–Langevin equations and calculated steady-state solutions, studied optical response through both analytical and numerical methods. The main focus of this study was optical response within the domain of position-dependent effective mass. Our findings revealed that the output field representing transmission exhibits variations and shift with $��\alpha �$, the nonlinear parameter of the position dependent effective mass. These variations not only impact transmission but also alter the dispersion and phase of the output field.

This work describes a molecular dynamics simulation study (MP2-DKH2/MM) that explores the structural and dynamical properties of hydrated Ac³⁺ ions in an aqueous solution. Simulation results indicate that the ion formed three hydration shells. The hydrated Ac³⁺ had a first hydration shell comprising 8–9 water molecules. It showed similar probabilities for both coordination numbers, showing a flexible first hydration shell with eight registered successful ligand exchanges during the simulation. The water molecules' mean residence times (MRT) in the first, second, and third hydration shells were 131.8, 6.46, and 2.67 ps, respectively. The complexes of octahydrate ([Ac(H₂O)₈]³⁺) and nonahydrate ([Ac(H₂O)₉]³⁺) were observed in the first hydration shell. The square antiprism (SA) geometry was adopted for octahydrate, while the gyroelongated square antiprism (GySA) geometry was adopted for nonahydrate. The simulations provided valuable insights into the ion-oxygen stretching frequencies. Specifically, the average stretching frequency for Ac³⁺ was found to be 404 cm⁻¹, which is in good agreement with the calculated value from the CCSD(T) calculation of 398.78 cm⁻¹. These findings indicate that including DKH2 relativistic approximation increases the accuracy of the simulation results and can contribute to understanding these actinide ions' behavior in aqueous environments, shedding light on hydrated systems' structural arrangements and dynamics.

Thermoelectric (TE) technology can effectively alleviate energy shortage and environmental pollution problems and has thus attracted extensive attention. In this work, we designed two unexplored two-dimensional materials, Ba₂ZnAs₂ and Ba₂ZnSb₂, and investigated their stability, mechanical characteristics, and TE properties using first-principles calculations and by solving the Boltzmann transport equation. We revealed that the two materials possess high stability and moderate cleavage energies of 0.84 and 0.76 J m⁻². Moreover, they are indirect semiconductors with band-gaps of 1.26 and 0.97 eV and show flat energy dispersion near the valence band maximum, resulting in a high p-type Seebeck coefficient of approximately 0.72 and 0.29 mV K⁻¹ at 300 K. Furthermore, they have significant anisotropic TE power factor along the a- and b-axis, with maxima of 1.19 and 0.75 mW m⁻¹ K⁻² at 300 K. Owing to the strong coupling between the acoustic and optical phonons, as well as the low frequency for low-lying phonons, the materials have high phonon scattering rates and low lattice thermal conductivities of 0.54/0.52 and 0.81/0.43 W mK⁻¹ along the a-/b-axis. Ultimately, Ba₂ZnAs₂ and Ba₂ZnSb₂ can deliver high-performance TE transport with high figures-of-merit of 0.32 and 0.19 at 300 K, which increase further to 1.67 and 0.91, respectively, at 700 K.

The interaction of H, H₂, and MgH₂ with graphene is investigated using the density functional theory to explore the possibility of exploiting graphene or functionalized graphene as a hydrogen storage medium. The H atom is positioned at various distances from the graphene surface and the energetics are computed in detail. The extent of interaction of the s electron of H with graphene's p_z electrons is well brought out. Similar investigations are carried out for H₂, MgH₂. In the case of H atom, a HC covalent bond is formed. This process turns out to be a prerequisite for proton transfer through graphene. Interactions of H₂ and MgH₂ with graphene are different from that of H. It leads to the conclusion that functionalized graphene will better substrate/candidate for applications like hydrogen storage.

In present work, using the double layer ONIOM methodology, we simulated the stages of initiation and growth of the polymer chain during the polymerization of butadiene on a neodymium-based Ziegler–Natta catalyst. The DFT methods B3LYP and PBE0 in combination with the Def2-TZVP atomic basis set were used as high-level methods in ONIOM. Grimme's semi-empirical XTB1 method was used as a low-level method. In our previous work, the mechanism of butadiene polymerization on a neodymium-containing Ziegler–Natta catalyst was studied in detail. The polymerization activation energy of 61 kJ/mol was found to be slightly higher than the experimentally determined values of this parameter. In the present work, the influence of a high-level method and a model of taking into account dispersion interactions on the quality of calculation of activation parameters of the polymerization reaction was studied. Experimental activation energy for the polymerization of dienes in the presence of Ziegler–Natta catalysts is in the range of 30–60 kJ/mol, but neodymium-based catalysts have an activation energy somewhat closer to the lower limit of this range. For comparison, semi-empirical Grimme models D3 and D4 were used. It has been established that the both models reveal within the B3LYP method the activation energy practically the same, while within the PBE0 method it decreases to 41 kJ/mol. Thus, using the PBE0 as a high-level method within the ONIOM methodology and taking into account dispersion interactions within the D4 model leads to results in much better agreement with experimental data.

Tungsten disulfide (WS₂) and hexagonal boron nitride (h-BN) monolayer, and h-BN/WS₂ heterojunction with low lattice mismatch is constructed using density functional theory (DFT). The band structures, density of states (DOS), charge density differences (CDD), work function (WF), adsorption energy and adsorption distance of h-BN/WS₂ heterojunction for six gases molecules (CO, CO₂, NO, NO₂, SO₂, and H₂S) are systematically discussed. Gas adsorption on one-side and both-sides of the heterojunction is considered. The results indicate that the band gap of the heterojunction is lower than that of h-BN and WS₂, indicating that the construction of heterojunction is beneficial for conductivity. For six gases, the adsorption energy of one-sided adsorption is significantly greater than that of both-sided adsorption, except for CO₂ and NO. The adsorption of NO and NO₂ introduces the magnetism into the system. Interestingly, the h-BN/WS₂ heterojunction demonstrates excellent selectivity for NO gas under one-sided and both-sided adsorption. The corresponding adsorption mechanism is explored.