International Journal of Quantum Chemistry最新文献

Benzophenone is a molecule with several extremely relevant characteristics, widely used as a type-2 photoinitiator due to its unique electronic properties and a very efficient intersystem crossing. In general, benzophenone can absorb directly to S₁ or S₂ states, but S₀ → S₁ transition is weak. Also, benzophenone has symmetric activity of the torsional modes of the phenyl groups, suggesting that is a non-rigid molecule. This work has two fundamental purposes. The first is to examine the ground state (S₀) and first singlet excited state (S₁) of benzophenone using TD-DFT methodology to generate the potential energy surface (PES) to understand its non-rigid behavior; and the second, to examine the Franck-Condon factors (FC factors) between the transition S₀ → S₁. From our results, the most accurate was the hybrid functional PBE0. From the PES analysis of S₀ and S₁ states, we observe that several minima were located and that they are separated by relative low energy barriers. The global minimum of S₀ is found at θ₁/θ₂ = 28.15° and for S₁ at θ₁/θ₂ = 20.71°. Interestingly, the PES of S₁ state shows a very extensive area of minimum energy and a local minimum located at θ₁ = 90.71°/θ₂ = 0.71°. From the vibrational spectra, we observe two intense signals that correspond to the symmetric phenyl twisting of normal mode 2 (2³ and 2⁴), and a combination between the symmetric hydrogen scissoring of 44¹ and 2³. As the vibronic spectrum tells, this transition is forbidden by the orbital theory but it is electronically allowed. Also, from the Duschinksy matrix, we observe a high mixing of vibrational modes.

Comparative exploration of structural, population analysis, mechanical, electronic, optical, and magnetic properties of a zinc-based single, non-toxic, inorganic halide-based novel perovskite compound RbZnX₃ (X = F, Cl, and Br) without applying pressure by using GGA-PBE functional within the CASTEP code. Systematic investigations show mechanically stable compound with lattice parameters of the unit cell 4.25, 5.01, 5.50 Å, with indirect bandgaps of 3.637, 1.387, 0.103 eV for RbZnF₃, RbZnCl₃, and RbZnBr₃ respectively. Band gap data shows that RbZnX₃ is a semiconductor in nature, and RbZnCl₃ can be an ideal photovoltaic material. From CDD analysis, all three perovskites show a combination of metallic and ionic bonding. Computed optical properties ensure this compound is beneficial in PES and EUV-based applications, like- anti-reflection surface coating and optoelectronics like solar cells, and it can be a promising element in radiation shielding, spectroscopy, and biotech fields, as well as in high absorption and infrared sectors. High reflectivity makes them suitable as solar cell coating material. Mechanical properties ensure these studied elements' ductility, machinability, and anisotropy. Absorption and reflectivity diminish where energy loss is maximum. For being diamagnetic, it is for superconductors, electromagnetic shielding, and materials testing sectors. Moreover, this study focuses on various applications and possibilities of this compound. Materials are found ductile and RbZnF₃ has an excellent shear and bulk modulus. RbZnF₃ exhibits more significant fracture and plastic deformation resistance than RbZnCl₃ and RbZnBr₃. Moderate elasticity, flexibility, and strength make these suitable for various applications. The phonon calculation indicates that RbZnF₃ exhibits dynamic stability, whereas instability has been observed in RbZnCl₃ and RbZnBr₃. An increase in Debye temperature correlates with improved elastic modulus, elevated sound velocity, and higher melting temperature. RbZnBr₃ shows higher heat capacity at (T < < θ_D) and shows higher energy dispersion or entropy.

In this work, the structures and electronic properties of anionic, neutral, and cationic TMPb₁₆^−/0/+ (TM = Sc, Y, Ti, Zr, Hf) clusters were studied through a genetic algorithm (GA) code with density functional theory (DFT) calculations. The results show that anionic TMPb₁₆⁻ (TM = Sc, Y, Ti, Zr) and neutral TMPb₁₆ (TM = Ti, Zr, Hf) clusters adopt the Frank–Kasper (FK) polyhedron as the geometric structure, while TMPb₁₆ (TM = Sc, Y, Hf⁻) and all cationic states of these clusters prefer a fullerene-like bitruncated square trapezohedron. In these clusters, the gain and loss of electrons in transition metals (TM) are similar and very small, with only Hf atom as the electron donor. The average binding energy of cationic TMPb₁₆ is 0.02 and 0.1 eV higher than that of its anionic and neutral states, respectively. All these TMPb₁₆ (TM = Sc⁻, Y⁻, Ti, Zr, Hf) clusters with 68 electrons show superatomic features with the electronic shell configuration of (1S)²(1P)⁶(1D)¹⁰(1F)¹⁴(2S)²(1G)¹⁸(2P)⁶(2D)¹⁰ as same as that of TMSn₁₆ (TM = Sc⁻, Y⁻, Ti, Zr, Hf) clusters.

Polytetrafluoroethylene (PTFE) is widely used in fields such as propellants and flame retardants. However, this is still a vacancy of detailed kinetic mechanisms to describe the complete decomposition of PTFE in the gas phase. The current work addresses this issue by conducting ab initio calculations for key reactions involved in the PTFE pyrolysis system. The potential energy surfaces (PESs) of PTFE unimolecular and bimolecular reactions are determined at the DLPNO-CCSD(T)/cc-pVTZ//B3LYP-D3/6–31++G(d,p) level. Rate constants and branching ratios of the main reaction pathways are calculated by solving the RRKM master equation, and the thermochemical properties of related species at the DLPNO-CCSD(T)/CBS level are calculated via the atomization method. The current study found that the initial decomposition of PTFE is dominated by the CC scission reactions and free radical (H, OH, CF, CF₂, and CF₃) abstraction reactions, forming the corresponding free radical species. Further β-CC scission reactions dominate the overall kinetics and continuously generate CF₂CF₂. Self-decomposition and free radical–driven decomposition of PTFE produce small molecules such as HF, FOH, CF₂, CF₃, and CF₄. This work provides quantitative predictions of the detailed decomposition reaction pathways of gas-phase PTFE and will lay a solid foundation for the development of detailed kinetic mechanisms for PTFE combustion and degradation.

This study employs first-principles computations to analyze ferrite spinels GeFe₂O₄ and SmFe₂O₄ using density functional theory (DFT). Structural stability calculations reveal that GeFe₂O₄ favors an antiferromagnetic phase, while SmFe₂O₄ stabilizes in a ferrimagnetic phase. Both compounds are elastically stable and ductile, and exhibit lattice constants consistent with experimental values, validating the reliability of the calculations. A significant drop in Debye temperature (from 495 to 233 K) occurs when Ge is replaced by Sm, while high melting temperatures indicate thermal stability over broad temperature ranges. The spin-polarized electronic band structure confirms the metallic nature of both materials. Furthermore, the Curie temperature and magnetic moment of SmFe₂O₄, calculated using Generalized Gradient Approximation (GGA + U) and the Heyd–Scuseria–Ernzerhof (HSE) methods, underline its potential for spintronic applications.

We systematically explored the adsorption, diffusion, thermodynamics stability, and electrochemical performance of halogen anions (F⁻, Cl⁻, Br⁻, I⁻) on monolayer InSe using first-principles calculations. F⁻, due to its strong electronegativity, has a destructive effect on the surface. The rank of the adsorption ability of other three anions is Cl⁻ > Br⁻ > I⁻ according to the value of adsorption energy, which is agreement with their electronegativity strength. It was found that the halogen anions exhibited excellent diffusion performance with low diffusion energy barriers. Cl⁻ can adsorb up to three layer showing an excellent theoretical capacity of 415 mA h g⁻¹, while Br⁻ and I⁻ cannot obtain a stable structure when the coverage exceeds 1 and (2/3) layer. In summary, this study evaluates a prospective electrode material and establishes a theoretical foundation for the development of novel rechargeable batteries.

Monte Carlo (MC) simulation and density functional theory (DFT) were employed to investigate the structural, mechanical, thermomagnetic, and electronic properties of the Co₂CrGa_1−xAl_x (x = 0, 0.25, 0.50, 0.75, and 1.0) full Heusler alloys. Both the pristine and doped configurations demonstrate the L2₁ prototype, and there is an observable decrease in the lattice parameter as the Al concentration rises. Electronic analysis was performed in Wien2k using the Perdew–Burke–Ernzerhof of generalized gradient approximation (GGA-PBE), the modified Becke–Johnson GGA (mBJ-GGA), and the PBEsol functional, which revealed a band gap in the spin-down states of both structures by studying the band structure and density of states. The phonon dispersion relation was studied to ensure the stability of the alloy. The magnetic moments in pristine configurations closely resemble those in doped structures, with minimal changes in exchange interaction parameters. The obtained Curie temperature, determined through the MC method, falls within the range of 321–500 K. Finally, studying the magnetic properties of the Heusler alloys can contribute to advancements in spintronics and other magnetic applications.