Journal of Computational Chemistry最新文献

In this study, nanocomposites of g-C₃N₄/MN₄ (where M is Mn, Fe and Co) have been designed using advanced density functional theory (DFT) calculations. A comprehensive analysis was conducted on the geometry, electronic, optical properties, work function, charge transfer interaction and adhesion energy of the g-C₃N₄/MN₄ heterostructures and concluded that g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterojunctions exhibit higher photocatalytic performance than individual units. The better photocatalytic activity can be attributed mainly by two facts; (i) the visible light absorption of both g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ interfaces are higher compared to its isolated analogs and (ii) a significant enhancement of band gap energy in g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterostructures limited the electron-hole recombination significantly. The potential of the g-C₃N₄/MN₄ heterojunctions as a photocatalyst for the water splitting reaction was assessed by examining its band alignment for water splitting reaction. Importantly, while the electronic and magnetic properties of MN₄ systems were studied, this is the first example of inclusion of MN₄ on graphene-based material (g-C₃N₄) for studying the photocatalytic activity. The state of the art DFT calculations emphasis that g-C₃N₄/FeN₄ and g-C₃N₄/CoN₄ heterojunctions are half metallic photocatalysts, which is limited till date.

The minimization of the commutator of the Fock and density matrices as the error matrix in the direct inversion of the iterative subspace (CDIIS) developed by Pulay is a powerful self-consistent field (SCF) acceleration technique for the construction of optimum Fock matrix, if initiated with a fair initial guess. In this work, we present an alternative minimized error matrix to the commutator in the CDIIS, namely the residual or the gradient of the energy-functional for a Slater determinant subject to the orthonormality constraints among orbitals, representing the search for a newly improved Fock matrix in the direction of the residual in the direct inversion of the iterative subspace (RDIIS). Implemented in the computational chemistry package GAMESS, the RDIIS is compared with the standard CDIIS and the second order SCF orbital optimization (SOSCF) for tested molecules started with a crude guess. As a result, the RDIIS stably and efficiently performs the SCF convergence acceleration. Furthermore, the RDIIS is considerably independent on the subspace size with the concentrated linear coefficients accounting proportionally for the Fock matrices close to the current iteration.

Metal halide perovskites are crystalline materials with a sharp increase in popularity and rapidly becoming a major contender for optoelectronic device applications. In this work, we provide the optoelectronic features of a possible novel candidate, ZSnCl₃ (Z = Na/K) Sn-based on a detailed numerical simulation. The output of the current computations is compared to the results that are currently available, and a respectable agreement is noted. The studied compounds were cubic in nature and structurally stabe. The mechanical properties reflect the mechanical stability and ductility of the proposed materials. The Sn-based single perovskite compounds proposed in this study are mechanically stable and ductile. The narrow direct band gap for NaSnCl₃ and KSnCl₃ are 1.36 eV and 1.47 eV, respectively, using the HSE06 hybrid function with the Boltztrp2 integrated in Quantum ESPRESSO (QE) software. The effective use of these compounds in perovskite solar cells and other optoelectronic applications was confirmed by optical absorption spectral measurements conducted in the photon energy range of 0-20 eV.

Empirical rovibrational energy levels are presented for the third most abundant, asymmetric carbon dioxide isotopologue, ¹⁶O¹²C¹⁸O, based on a compiled dataset of experimental rovibrational transitions collected from the literature. The 52 literature sources utilized provide 19,438 measured lines with unique assignments in the wavenumber range of 2-12,676 cm^-1. The MARVEL (Measured Active Rotational-Vibrational Energy Levels) protocol, which is built upon the theory of spectroscopic networks, validates the great majority of these transitions and outputs 8786 empirical rovibrational energy levels with an uncertainty estimation based on the experimental uncertainties of the transitions. Issues found in the literature data, such as misassignment of quantum numbers, typographical errors, and misidentifications, are fixed before including them in the final MARVEL dataset and analysis. Comparison of the empirical energy-level data of this study with those in the line lists CDSD-2019 and Ames-2021 shows good overall agreement, significantly better for CDSD-2019; some issues raised by these comparisons are discussed.

High-level multireference and coupled cluster quantum calculations were employed to analyze low-lying electronic states of linear-MNX⁺ and side-bonded-M[NX]⁺ (M = Ca, Sr, Ba, Ra; X = O, S, Se, Te, Po) species. Their full potential energy curves (PECs), dissociation energies (D_es), geometric parameters, excitation energies (T_es), and harmonic vibrational frequencies (ω_es) are reported. The first three chemically bound electronic states of MNX⁺ and M[NX]⁺ are ³∑^-, ¹Δ, ¹∑⁺ and ³A″, ¹A', ¹A″, respectively. The ³∑^-, ¹Δ, ¹∑⁺ of MNX⁺ originate from the M⁺(²D) + NX(²Π) fragments, whereas the ³A″, ¹A', ¹A″ states of M[NX]⁺ dissociate to M⁺(²S) + NX(²Π) as a result of avoided crossings. The MNX⁺ and M[NX]⁺ are real minima on the potential energy surface and their interconversions are possible. The M²⁺NX^-/M²⁺[NX]^- ionic structure is an accurate representation for their low-lying electronic states. The D_es of MNX⁺ species were found to depend on the dipole moment (μ) of the corresponding NX ligands and a linear relationship between these two parameters was observed.

The electronic structure of the strongly correlated electron system plutonium hexaboride is studied by using single-particle approximations and a many-body approach. Imaginary components of impurity Green's functions show that 5f_j=5/2 and 5f_j=7/2 manifolds are in conducting and insulating regimes, respectively. Quasi-particle weights and their ratio suggest that the intermediate coupling mechanism is applicable for Pu 5f electrons, and PuB₆ might be in the orbital-selective localized state. The weighted summation of occupation probabilities yields the interconfiguration fluctuation and average occupation number of 5f electrons n_5f ~ 5.101. The interplay of 5f-5f correlation, spin-orbit coupling, Hund's exchange interaction, many-body transition of 5f configurations, and final state effects might be responsible for the quasiparticle multiplets in electronic spectrum functions. Prominent characters in the density of state, such as the coexistence of atomic multiplet peaks in the vicinity of the Fermi level and broad Hubbard bands in the high-lying regime, suggest that PuB₆ could be identified as a Racah material. Finally, the quasiparticle band structure is also presented.

In this work, the theory of the modified unit sphere representation (mUSR) has been proposed as a computational tool suitable for the three-dimensional representation of the pure electric-dipole [ ${\beta }_{\lambda \mu \nu }(-2\omega ;\omega ,\omega )$ ] as well as of the mixed electric-dipole/magnetic-dipole [ ${\hspace{0.17em}}^{\alpha }{J}_{\lambda \mu \nu }(-2\omega ;\omega ,\omega )$ and ${\hspace{0.17em}}^{\beta }{J}_{\lambda \mu \nu }(-2\omega ;\omega ,\omega )$ ] or electric-dipole/electric-quadrupole [ ${\hspace{0.17em}}^{\alpha }{K}_{\lambda \mu \nu o}(-2\omega ;\omega ,\omega )$ and ${\hspace{0.17em}}^{\beta }{K}_{\lambda \mu \nu o}(-2\omega ;\omega ,\omega )$ ] first hyperpolarizabilities. These five quantities are Cartesian tensors and they are responsible for the chiral signal in the chiroptical version of the hyper-Rayleigh scattering (HRS) spectroscopy, namely the HRS optical activity (HRS-OA) spectroscopy. For the first time, for each hyperpolarizability, alongside with the three-dimensional representation of the whole (i.e., reducible) Cartesian tensors, the mUSRs are developed for each of the irreducible Cartesian tensors (ICTs) that constitute them. This scheme has been applied to a series of three (chiral) hexahelicene molecules containing different degrees of electron-withdrawing (quinone) groups and characterized by the same (positive) handedness. For these molecules, the mUSR shows that, upon substitution, the most remarkable qualitative and semi-quantitative (enhancement of the molecular responses) effects are obtained for the pure electric-dipole and for the mixed electric-dipole/magnetic-dipole hyperpolarizabilities.

The fluxional nature of halogen bonds (XBs) in small molecular clusters, supramolecules, and molecular crystals has received considerable attention in recent years. In this work, based on extensive density-functional theory calculations and detailed electrostatic potential (ESP), natural bonding orbital (NBO), non-covalent interactions-reduced density gradient (NCI-RDG), and quantum theory of atoms in molecules (QTAIM) analyses, we unveil the existence of fluxional halogen bonds (FXBs) in a series of linear (IC₆F₄I)_m(OONC₆H₄NOO)_n (m + n = 2-5) complexes of tetrafluorodiiodobenzene with dinitrobenzene which appear to be similar to the previously reported fluxional hydrogen bonds (FHBs) in small water clusters (H₂O)_n (n = 2-6). The obtained $\mathrm{GS}\rightleftharpoons \mathrm{TS}\rightleftharpoons {\mathrm{GS}}^{\text{'}}$ fluxional mechanisms involve one FXB in the systems which fluctuates reversibly between two linear CI···O XBs in the ground states (GS and GS') via a bifurcated CI  O₂N van der Waals interaction in the transition state (TS). The cohesive energies (E_coh) of these complexes with up to four XBs exhibit an almost perfect linear relationship with the numbers of XBs in the systems, with the average calculated halogen bond energy of E_coh/XB = 3.48 kcal·mol^-1 in the ground states which appears to be about 55% of the average calculated hydrogen bond energy (E_coh/HB = 6.28 kcal·mol^-1) in small water clusters.

The development of palladium-catalyzed fluorination with biaryl monophosphine ligands has faced two important problems that limit its application for bromoarenes: the formation of regioisomers and insufficient catalysis for heteroaryl substrates as bromothiophene derivatives. Overcoming these problems requires more ligand design. In this work, reliable theoretical calculations were used to elucidate important ligand features necessary for achieving more rate acceleration and selectivity. These features include increasing the ligand-substrate repulsion and creating a negative charge in the space around the fluoride ion bonded to the palladium. The investigated L5 ligand presents these features, and the calculations predict that this ligand completely suppresses the regioisomer formation in the difficult case of 4-bromoanisole. In addition, the free energy barriers are decreased by 2-3 kcal mol^-1 in comparison with the catalysis involving the AlPhos ligand. Thus, the present study points out a direction for new developments in palladium-catalyzed fluorination.