Analysis Of Wave Functions Research Articles

Quantum dynamics study of C—H stretching vibrational excitation in the F+CHD<sub>3</sub> → HF+CD<sub>3</sub> reaction

In recent decades, significant progress has been made in the precise theoretical investigation of gas-phase chemical reactions. Presently, a major challenge in the field of quantum dynamics is to develop the precise methodologies for studying chemical reactions involving more than four atoms. As a typical multi-atomic reaction system, the F+CH<sub>4</sub> reaction and its isotopic substitution reactions have attracted widespread attention from both experimental and theoretical perspectives in recent years. Experimental studies on the reaction of F+CHD<sub>3</sub> have revealed that the stretching vibration excitation of the C—H bond inhibits the bond dissociation, favoring the formation of DF+CHD<sub>2</sub> product channels. In this study, we use a seven-dimensional quantum time-dependent wave packet method to investigate the dynamics of the F+CHD<sub>3</sub> reaction in both the reactant vibrational ground state and the first stretching excited state of the C—H bond. In this work, the reaction probabilities under different vibrational conditions are analyzed, showing that when the collision energy is below 0.06 eV, the reaction probability curves exhibit numerous fast-oscillating peaks, supporting the experimentally suggested phenomena of dynamic resonance. In a collision energy range from 0.06 eV to 0.3 eV, the reaction probability for the HF product channel in the vibrational excited state is lower than that in the ground state, which is consistent with experimental observation. Through the analysis of the time-independent wave functions of product channels under low-energy collision conditions, it is found that for reactions involving vibrational ground states, the HF products in the product asymptotic region and the reaction transition state region are in the <i>v'</i> = 2 excited state and <i>v'</i> = 3 excited state of stretching vibration, respectively, which are consistent with previous experimental observations and six-dimensional quantum wave packet simulations. For reactions involving the first excited state of C—H stretching vibration, the HF products in the product asymptotic region and the reaction transition state region are both in the <i>v'</i> = 3 excited state of stretching vibration, which are consistent with the results obtained based on energy analysis. Simulation results indicate that in the case of low-energy collisions, the time-independent wave function for the C—H stretching vibrational excited state tends to be closer to the D atom side in the transition state region. This phenomenon is attributed to the more significant energy advantage of the vibrational excited state potential energy surface in the large collision angle region, explaining the inhibitory effect of stretching vibration excitation on the HF product channel. This study offers important theoretical support for explaining experimental results and contributes to a more in-depth understanding of the influence of vibrational mode excitations on the dynamical processes in poly-atomic reactions.

Natural resonance-theoretic conceptions of extreme electronic delocalization in soft materials.

In the broad context of Dalton's atomic hypothesis and subsequent classical vs. quantum understanding of macroscopic materials, we show how Pauling's resonance-type conceptions, as quantified in natural resonance theory (NRT) analysis of modern wavefunctions, can be modified to unify description of interatomic interactions from the Lewis-like limit of localized e-pair covalency in molecules to the extreme delocalized limit of supramolecular "soft matter" aggregation. Such "NRT-centric" integration of NRT bond orders for hard- and soft-matter interactions is illustrated with application to a long-predicted and recently synthesized organometallic sandwich-type complex ("diberyllocene") that exhibits bond orders ranging from the soft limit (bBeC ≈ 0.01) to the typical values (bCC ≈ 1.35) of molecular resonance-covalency in the organic domain, with intermediate value (bBeBe ≈ 0.86) for intermetallic Be⋯Be interaction.

Intermolecular interaction characteristics of the Boron‐nitrogen rings, and with hexagonal boron nitride: A special molecular adsorption and weak interaction

AbstractWith the discovery of cyclo[18]carbon, related theoretical research has become a very hot topic. Due to its unique molecular structure, many derivatives have been derived, especially its isoelectronic molecule cyclo B9N9. This work focused on the interaction between cyclo B9N9 molecules and explored the nature of their interaction. The interaction of the dimer of cyclo B9N9 was studied, quantum chemical calculation and wave function analysis were carried out, and compared with cyclo[18]carbon to find its commonness. It showed that the interaction between the cyclo B9N9 dimers is a weak electron generating stacking interaction. In addition, the adsorption of cyclo B9N9 was studied, and the interaction of graphene analogues hexagonal boron nitride (h‐BN). Through calculation and analysis, it was found that the adsorption of cyclo B9N9 was much stronger than that of cyclo[18]carbon. In another sense, the π–π stacking interaction of boron nitrogen structure is stronger than that of carbon. To further validate this commonality, B6N6 was selected for the same calculation, and similar conclusions were obtained. It was also found that the more Boron nitrogen (BN), the stronger the stacking interaction.

Molecular structure, different solvents interaction, thermodynamic, electronic, topological, and chemical behaviors of cis-2,6-dimethylpiperazin- anti depression agent

The Cis-2,6-Dimethylpiperazin has undergone wave function analysis to determine the topological characteristics. The vibrational and ultraviolet-visible spectroscopy investigations were carried out. By advocating Density Functional Theory as a technique, the optimized structure is computed. Polarizability, nucleophilicity, and electrophilicity have also been estimated using Non-Linear Optics, Fukui, and Molecular Electro Static Potential. Additionally, the Highest occupied molecular orbital to Lowest unoccupied molecular orbital studies were carried out to know biological activity. It has been hypothesized that drug-like properties can explain a biological reaction. We predicted and examined the various thermodynamic properties. In addition to previous studies, the docking process was employed to calculate the energies of binding and size of bonding hydrogen with various proteins. This work describes molecular, electrical, chemical, and biological actions.

Thermodynamic and molecular insights into the separation of ethanol/ethyl propionate by extraction using low transition temperature mixtures

Low-transition temperature mixtures (LTTMs) have been proposed as green solvents for the separation of ethanol (EtOH)/ethyl propionate (EtPa) azeotropes. COSMO-SAC model was used to screen LTTMs, and ammonium acetate, ethylammonium chloride, and choline chloride were selected as hydrogen bond acceptors to form LTTMs with ethylene glycol. Liquid-liquid phase equilibrium experiments were carried out for the screened LTTMs and the separation system to confirm the validity of the selected solvents. And the distribution coefficients of EtOH in the three LTTMs were all greater than 1.2, and the selectivity for EtOH ranged from 6 to 50. The separation mechanism at the molecular level was revealed through quantum chemical calculations and wave function analysis. The thermodynamic behavior of the EtOH/EtPa/LTTMs system and the role of hydrogen bonding interactions were systematically investigated. The results indicated that electrostatic forces are the main molecular interactions, and the stronger interaction of LTTMs with ethanol is the basis for achieving the azeotropic separation.

Raman spectroscopy and quantum chemical calculation on SmCl3-KCl-LiCl molten salt system

The study on the ionic structure of SmCl3-KCl-LiCl molten systems is of guiding significance for the practical production of metal samarium and samarium alloys via Molten salt electrolysis (MSE) using this system as electrolyte. Based on density functional theory (DFT), the possible ionic groups in SmCl3-KCl-LiCl molten system were simulated by Gaussian and GaussView program and their theoretical Raman spectra were calculated. The calculated spectra were then compared with the experimental Raman spectra of molten 0.1–2 mol% SmCl3-(41 mol% KCl-59 mol% LiCl) to identify the ionic groups which might have existed. It is thought that SmCl4-, SmCl63-, Sm2Cl82- and Sm2Cl7- exist in the molten system. When the temperature is unchanged, the “lifetime” of SmCl63- is reduced while those of SmCl4-, Sm2Cl82- and Sm2Cl7- is increased with the increase of SmCl3 content. Within the temperature range of 773–809 K, when the content of SmCl3 remains unchanged, the “lifetime” of these complex ions decreases with the increase of temperature. Besides, the relative content of SmCl63- decreases with the increase of temperature. The wave function analysis of the four kinds of Sm-Cl ionic groups was also carried out using Multiwfn program. The net atomic charge of each ionic group, the direction of electron migration during the formation of the ionic groups, as well as the most prone to electrophilic and nuclear reactions of each ionic group, and the order of bond breaking during chemical reactions for the four groups were obtained.

Local Oxidation States in {FeNO}6-8 Porphyrins: Insights from DMRG/CASSCF-CASPT2 Calculations.

A first DMRG/CASSCF-CASPT2 study of a series of paradigmatic {FeNO}6, {FeNO}7, and {FeNO}8 heme-nitrosyl complexes has led to substantial new insight as well as uncovered key shortcomings of the DFT approach. By virtue of its balanced treatment of static and dynamic correlation, the calculations have provided some of the most authoritative information available to date on the energetics of low- versus high-spin states of different classes of heme-nitrosyl complexes. Thus, the calculations indicate low doublet-quartet gaps of 1-4 kcal/mol for {FeNO}7 complexes and high singlet-triplet gaps of ≳20 kcal/mol for both {FeNO}6 and {FeNO}8 complexes. In contrast, DFT calculations yield widely divergent spin state gaps as a function of the exchange-correlation functional. DMRG-CASSCF calculations also help calibrate DFT spin densities for {FeNO}7 complexes, pointing to those obtained from classic pure functionals as the most accurate. The general picture appears to be that nearly all the spin density of Fe[P](NO) is localized on the Fe, while the axial ligand imidazole (ImH) in Fe[P](NO)(ImH) pushes a part of the spin density onto the NO moiety. An analysis of the DMRG-CASSCF wave function in terms of localized orbitals and of the resulting configuration state functions in terms of resonance forms with varying NO(π*) occupancies has allowed us to address the longstanding question of local oxidation states in heme-nitrosyl complexes. The analysis indicates NO(neutral) resonance forms [i.e., Fe(II)-NO0 and Fe(III)-NO0] as the major contributors to both {FeNO}6 and {FeNO}7 complexes. This finding is at variance with the common formulation of {FeNO}6 hemes as Fe(II)-NO+ species but is consonant with an Fe L-edge XAS analysis by Solomon and co-workers. For the {FeNO}8 complex {Fe[P](NO)}-, our analysis suggests a resonance hybrid description: Fe(I)-NO0 ↔ Fe(II)-NO-, in agreement with earlier DFT studies. Vibrational analyses of the compounds studied indicate an imperfect but fair correlation between the NO stretching frequency and NO(π*) occupancy, highlighting the usefulness of vibrational data as a preliminary indicator of the NO oxidation state.

Topological analysis and reactivity study of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone: a computational study.

Quinolone derivatives have gathered major attention largely due to their wonderful biological activities. Quinolones are a class of molecules that are derived from quinolines and also extracted from natural sources. Most of these quinolones have significant medicinal properties ranging from antiallergenic and anticancer to antimicrobial activities. Some bacteria produce several 2-alkyl-4(1H)-quinolones. In past years, a variety of methods have been reported for the synthesis of quinolone derivatives. In this present work, structural, wave functional, and electronic properties of monomeric and dimeric forms of 2-methyl-4(1H)-quinolone are investigated. From the calculated binding energies, it was found that the formation of dimers is thermodynamically favorable. The analysis of reactivity parameters confirms that the keto form is more reactive than the enol form and keto-keto dimer is more reactive than compared to all monomeric and dimeric forms of our studied compound. Geometry optimizations of monomers and dimers of studied molecules were carried out using the B3LYP-D3(BJ)/ma-def2-TZVPP level of theory. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were calculated using the B3LYP/def2-TZVP level of theory. All DFT calculations were done with the ORCA 5.0.3 program. The reactivity parameters such as ionization potential, electron affinity, global hardness, global softness, electronegativity, chemical potential, and electrophilicity index were calculated. The nature of intermolecular interactions within the dimers was studied using topological analysis such as atoms in molecule (AIM) and reduced density gradient (RDG) surface analyses. To visualize the electron delocalization in the dimer electron localization function (ELF) and localized orbital locator (LOL) studies were also performed. The analyses such as AIM, RDG, ELF, and LOL were carried out by the multifunctional wavefunction analysis program Multiwfn 3.8.

Effective electrostatic potential surface and aromatic affinity as quantitative guide for deep extraction denitrification from aromatic-rich oils

High polar and reactive nitrogen-containing compounds greatly hinder the application of slurry oil (SO) in carbon-based materials. Compared with the hydrodenitrification process, the extraction process avoids aromatic saturation. However, pure experiments could not effectively screen extractants because of the structural similarity of polycyclic aromatic hydrocarbon (PAH) and nitrogen-containing PAH (NC-PAH). This work focused on searching for deep eutectic solvents (DESs) through sequential theoretical screening methods. The contradiction between denitrification efficiency (DN) and PAH loss (PL) could be weakened. Firstly, column chromatography, GC–MS, etc. were used to determine the molecular structure. The σ-profile, which performs the hydrogen bond acceptors (HBAs) property of molecules, was employed to crudely screen HBAs. Then, the interaction mechanism was obtained by multiple wave function analyses. An index named effective electrostatic potential (ESP) surface area, coined EES, was defined as the area of the region that apparently affected the interaction to predict DN. Additionally, the interaction energy (IE) of the cation of HBAs and non-basic PAH (nNC-PAH) was used to assess aromatic affinity and PL. The IE of HBAs and nNC-PAH linearly increased with EES, R2 = 0.9558. Meanwhile, DN was positively and linearly correlated with IE. Moreover, PL decreased slightly, then sharply, with the increase in aromatic affinity. The DN could reach about 65.1%, and the PL was limited to 3.8% after searching for high DN by EES and excluding high PL by aromatic affinity. These denitrification performances are crucially beneficial to the further preparation of carbon materials.

The Equilibrium Molecular Structure of Cyclic (Alkyl)(Amino) Carbene Copper(I) Chloride via Gas-Phase Electron Diffraction and Quantum Chemical Calculations.

Copper-centered carbene-metal-halides (CMHs) with cyclic (alkyl)(amino) carbenes (CAACs) are bright phosphorescent emitters and key precursors in the synthesis of the highly promising class of the materials carbene-metal-amides (CMAs) operating via thermally activated delayed fluorescence (TADF). Aiming to reveal the molecular geometry for CMH phosphors in the absence of the intermolecular contacts, we report here the equilibrium molecular structure of the (CAAC)Cu(I)Cl (1) molecule in the gas-phase. We demonstrate that linear geometry around a copper atom shows no distortions in the ground state. The structure of complex 1 has been determined using the electron diffraction method, supported by quantum chemical calculations with RI-MP2/def2-QZVPP level of theory and compared with the crystal structure determined by X-ray diffraction analysis. Mean vibrational amplitudes, uij,h1, and anharmonic vibrational corrections (rij,e • rij,a) were calculated for experimental temperature T = 20 °C, using quadratic and cubic force constants, respectively. The quantum theory of atoms in molecules (QTAIM) and natural bond order (NBO) analysis of wave function at MN15/def2TZVP level of theory revealed two Cu…H, three H…H, and one three-center H…H…H bond paths with bond critical points. NBO analysis also revealed three-center, four-electron hyperbonds, (3c4e), [π(N-C) nπ(Cu) ↔ nπ(N) π(N-Cu)], or [N-C: Cu ↔ N: C-Cu] and nπ(Cu) → π(C-N)* hyperconjugation, that is the delocalization of the lone electron pair of Cu atom into the antibonding orbital of C-N bond.

DFT Studies on the Mechanisms of Carboamination/Diamination of Unactivated Alkenes Mediated by Pd(IV) Intermediates.

Density functional theory (DFT) calculations have been employed to investigate the mechanism of carboamination and diamination of unactivated alkenes mediated by Pd(IV) intermediates. Both reactions share a common Pd(IV) intermediate, serving as the starting point for either the carboamination or the diamination pathway. The formation of this Pd(IV) intermediate encompasses a transition state that substantially impacts the turnover frequency (TOF) of catalytic cycles, with an apparent activation free-energy barrier of 26.1 kcal mol-1. Carboamination of unactivated alkenes proceeds through the coordination of a toluene molecule, C-H activation, inner reductive elimination, and the separation of the carboamination product from this intermediate, while diamination of unactivated alkenes involves the formation of the ion nucleophile, SN2 attack, and the separation of the diamination product. A comparison of the free-energy profiles for carboamination and diamination of unactivated alkenes can elucidate the origin of the chemoselectivity, and Bader's atoms in molecules (AIM) wave function analyses have been performed to analyze the contributions of the outer C-N bonding in the diamination process.

Density functional theory studies on properties of cluster ConMoS (n=1 ~ 5): interatomic interactions, electronic properties, frontier orbitals.

To comprehend the microscopic property alterations within the ConMoS cluster (n=1-5), this study investigates its internal interactions, electronic characteristics, and orbital correlations employing density functional theory. Structural optimization and theoretical analysis of the cluster are conducted using the Gaussian09 software package, considering various spin multiplicities and employing the B3LYP/def2tzvp quantum chemical method as the computational standard. The outcomes reveal the optimization of the cluster, resulting in 21 stable configurations while continually acquiring energy from the external environment. Analysis of the interaction region indicator functions, the independent gradient model based on Hirshfeld partition, the localized orbital indicator functions, and the electron localization function reveals a trend toward chemical bonding interactions within the interatomic interaction regions. Moreover, the interatomic forces exhibit a high likelihood of engaging in covalent bonding interactions. Both Co and Mo atoms display greater electron delocalization, facilitating the exchange of electrons with the external environment. The paper discuss electron space range, hardness and softness, polarizability, dipole moment, Mulliken population analysis, density of states, HOMO-LUMO diagram, and UV-Vis spectra. Configuration 5a exhibits the broadest electron delocalization and the highest reactivity. It maintains structural stability in external conditions and displays the most polarized molecules. Metal atoms in this cluster exhibit superior mobility compared to non-metal atoms. We elucidate the electron density aggregation region within the cluster. Configuration 1a demonstrates the highest correlation with molar absorption coefficient for its peak. Analyzing the HOMO and LUMO orbital delocalization index and center-of-mass distances revealed that the front orbits of configuration 5a exhibited a broad distribution in space and the minimum center-of-mass distance. This study presents a theoretical investigation of Co-Mo-S clusters employing density functional theory (DFT). DFT is a prevalent method for exploring the electronic structure and characteristics of atoms, molecules, and solids. The paper examines cluster attributes encompassing interatomic interactions, electronic properties, and frontier orbitals. Gaussian09 software is employed for optimizing cluster structures, while the analysis is augmented using Multiwfn wave function analysis software. By harnessing these theoretical and computational tools, it aims to delve deeper into cluster properties, yielding valuable insights.

Improved electrochemical detection of copper ions in nitrogen doped ta-C films for marine corrosive monitoring

The corrosion of copper-based alloy in the harsh marine environment threatens the reliable operation and service life of marine engineering equipment. In this work, the nitrogen modified tetrahedral amorphous carbon (ta-C:N) film electrodes were prepared for marine-oriented copper ions detection. The relationship between structural evolution and electrochemical performance of ta-C:N film electrode tailored by N2 flux was evaluated. The sp2 cluster and the content of sp2-bonded carbon in ta-C:N film were promoted with the increase of N2 flux. XPS results indicated that the variation of N2 flux modified the nitrogen-containing groups of the ta-C:N film electrodes. The optimized ta-C:N film electrode deposited at N2 flux of 3 sccm showed a quasi-reversible electrode behaviors. Moreover, the ta-C:N film electrode exhibited a linear range from 8 × 10−3 mM to 5 mΜ, a detection limit of 8 × 10−3 mM, and good repeatability and reproducibility for Cu2+ detection in 3.5 wt% NaCl solution. The improved Cu2+ sensing properties were ascribed to the enhanced sp2 cluster and the introduction of multiple nitrogen-containing functional groups, especially the pyrrolic nitrogen and graphitic nitrogen. DFT computation and wavefunction analysis revealed that the pyrrolic nitrogen possessed the strongest interaction for copper ions among different nitrogen configurations.

Lithium isotope separation by precipitation method coupled with solvent extraction with 1-Hydroxy-4-(p-toluidino) anthraquinone

This paper reported a novel chelating agent and a green precipitation-extraction separation strategy for lithium isotope enrichment. 1-Hydroxy-4-(p-toluidino) anthraquinone and anisole were used as chelating agent and diluent, respectively. Three phases including organic phase, aqueous phase and precipitation could be preparated. The experiment indicated that excess sodium hydroxide was helpful to promote the single-stage precipitation rate and equilibrium time. The isotope result indicated that 6Li was concentrated in the aqueous phase and 7Li was concentrated in precipitation phase. The maximum single-stage lithium isotope speration factor reached to 1.013 ± 0.001. By doing thermodynamic analysis of the reaction, the free energy change (ΔG), enthalpy change (ΔH) and entropy change(ΔS) of the separation process were −8.97 J mol−1, −21.37 J mol−1 and −0.0438 J mol−1 K−1 at 283 K. The results of DFT simulation and wave function analysis indicated that a lithium ion combined with a chelating agent anion formed a stable six-member ring between two oxygen, which was more stable than sodium ions combined with chelating agent anions (the Gibbs free energy of the lithium ions reaction was more negative). As interaction analysis result showed, the Li-O bond in complex interaction was significantly stronger than the Li-O bond interaction in aqueous phase, which was the theroy that led to the enrichment of 7Li in organic phase. In the activated carbon treatment experiment, it was found that part of lithium chelator solved in aqueous phase, which resulted in that the lithium abundance of aqueous phase hardly changed. In order to increase the abundance of 6Li in aqueous phase, it is necessary to add adjuvant to reduce the water solubility of lithium chelate. Overall, an economical and environmental-friendly precipitation method with a certain application prospect for lithium isotope separation was proposed, and the direction of improving the separation performance was pointed out in this paper.

Three heteroleptic copper(I) complexes with [Cu(P˄P)N2]+ structure and their fluorescence sensing for VOCs

The design and research of luminescent and volatile organic compound (VOC) fluorescent sensing materials are of great significance and challenge. We report herein the ligand substitution reaction and VOC sensing of new heteroleptic [Cu(P˄P)N2]+ type copper(I) complexes. Firstly, three new complexes 1–3 were designed by utilizing a chelate diphosphine ligand 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene (Xantphos) and synthesized by the substitution reaction of different N‐containing ligands of 4‐PBO (1), 3‐PBO (2), and 4,4′‐Bipy (3) (4‐PBO = 2‐(4′‐pyridyl)‐benzoxazole, 3‐PBO = 2‐(3′‐pyridyl)‐benzoxazole, 4,4′‐Bipy = 4,4′‐bipyridine), respectively. Three complexes were characterized by elemental analysis, spectroscopic analysis (IR, UV–Vis), single‐crystal X‐ray diffraction (SCXRD), and photoluminescence study. The SCXRD study revealed that complexes 1 and 2 both exhibit a molecular structure with tetrahedral copper(I) complex cation and hexafluorophosphate anion, while complex 3 differs in that its cation is a binuclear copper(I) structure bridged by 4,4′‐bipyridine. Three complexes 1–3 present supramolecular ribbon, supramolecular dimer, and supramolecular framework structure, respectively. Some differences of their UV–Vis absorption spectra were explained by TD‐DFT calculation and wavefunction analysis. It is found that 1 has an abnormal luminescence blue shift, and a luminescence mechanism through the high‐energy T2 excited state is proposed by TD‐DFT calculation. Based on 3, a fluorescent test strip was developed, and its fast and selective fluorescent sensing of pyridine vapor through quenching mechanism was successfully realized. The fluorescent quenching mechanism of the material was also studied, and it was proposed that the quenching should be attributed to the photoinduced electron transfer (PET) mechanism.

Investigating the mechanism behind the synergistic ultraviolet photooxidation degradation of gaseous benzene through modified ACF

The effects of relative humidity were studied on the direct conversion efficiency, mineralization rate and components of waste gas from benzene photooxidation degradation. The adsorption energies, adsorption types, and molecular interaction forces of activated carbon fiber (ACF) modified with nitrogen and oxygen-containing functional groups were calculated using quantum chemical density functional theory (DFT) calculations and wave function analysis. Five polar intermediate products including acetone, acetol, hexanal, benzaldehyde, and acetophenone generated from benzene photooxidation degradation were selected as the computational object. The independent gradient model method based on Hirshfeld partition was used to study the weak interactions among the five equilibrium molecular adsorption configurations. The results demonstrated that the direct conversion efficiency of benzene increased first and then decreased with increasing relative humidity. The maximum direct conversion efficiency was 82% observed at a relative humidity of 50%. The mineralization rate decreased significantly at higher relative humidity, and the lowest value was 2%. The overall adsorption effect of nitrogen-containing functional groups on the modified ACF surface is higher than that of oxygen-containing functional groups. The functional groups with the best adsorption effect are ACF modified by pyridone, amino and carboxyl groups. Combined with electron localization function (ELF) analysis and Mayer bond-level calculation, it was found that all the modified ACF surfaces do not form chemical bonds for the equilibrium molecular adsorption configurations of the five organic compounds, which belong to physical adsorption. The adsorption of five intermediate products by modified ACF mainly depended on hydrogen bonds or van der Waals forces. The existence of hydrogen bonds greatly improved the adsorption capacity of modified ACF to organic molecules.

Toward Benchmark-Quality Ab Initio Predictions for 3d Transition Metal Electrocatalysts: A Comparison of CCSD(T) and ph-AFQMC.

Generating accurate ab initio ionization energies for transition metal complexes is an important step toward the accurate computational description of their electrocatalytic reactions. Benchmark-quality data is required for testing existing theoretical methods and developing new ones but is complicated to obtain for many transition metal compounds due to the potential presence of both strong dynamical and static electron correlation. In this regime, it is questionable whether the so-called gold standard, coupled cluster with singles, doubles, and perturbative triples (CCSD(T)), provides the desired level of accuracy─roughly 1-3 kcal/mol. In this work, we compiled a test set of 28 3d metal-containing molecules relevant to homogeneous electrocatalysis (termed 3dTMV) and computed their vertical ionization energies (ionization potentials) with CCSD(T) and phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) in the def2-SVP basis set. A substantial effort has been made to converge away the phaseless bias in the ph-AFQMC reference values. We assess a wide variety of multireference diagnostics and find that spin-symmetry breaking of the CCSD wave function and the PBE0 density functional correlate well with our analysis of multiconfigurational wave functions. We propose quantitative criteria based on symmetry breaking to delineate correlation regimes inside of which appropriately performed CCSD(T) can produce mean absolute deviations from the ph-AFQMC reference values of roughly 2 kcal/mol or less and outside of which CCSD(T) is expected to fail. We also present a preliminary assessment of density functional theory (DFT) functionals on the 3dTMV set.

Theoretical Study on the Coordination and Separation Capacity of Macrocyclic N-Donor Extractants for Am(III)/Eu(III).

Designing ligands that can effectively separate actinide An(III)/lanthanide Ln(III) in the solvent extraction process remains one of the key issues in the treatment of accumulated spent nuclear fuel. Nitrogen donor ligands are considered as promising extractants for the separation of An(III) and Ln(III) due to their environmental friendliness. Four new macrocyclic N-donor hexadentate extractants were designed and their coordination with Am(III) and Eu(III), as well as their extraction selectivity and separation performance for Am(III) and Eu(III), were investigated by scalar relativistic density functional theory. A variety of theoretical methods have been used to evaluate the properties of the four ligands and the coordination structures, bonding properties, and thermodynamic properties of the complexes formed by the four ligands with Am(III) and Eu(III). The results of various wavefunction analysis methods including NBO analysis, quantum theory of atoms in molecules (QTAIM) analysis, and so on show that Am(III) has a stronger coordination ability with the ligands than Eu(III) due to the Am 5f orbitals more involved in bonding with the ligands than the Eu 4f orbitals, and the bonding environment of the N-donor in the ligand has a significant effect on its coordination ability of the metal ions. Thermodynamic analysis of the solvent extraction process shows that all of the four N-containing macrocyclic ligands have good extraction selectivity and separation performance for Am(III) and Eu(III). This study provides theoretical support for designing potential nitrogen-containing macrocyclic extractants with excellent separation performance.

Simple, Efficient, and Universal Energy Decomposition Analysis Method Based on Dispersion-Corrected Density Functional Theory.

Energy decomposition analysis (EDA) is an important class of methods to explore the nature of interaction between fragments in a chemical system. It can decompose the interaction energy into different physical components to understand the factors that play key roles in the interaction. This work proposes an EDA strategy based on dispersion-corrected density functional theory (DFT), called sobEDA. This method is fairly easy to implement and very universal. It can be used to study weak interactions, chemical bond interactions, open-shell systems, and interactions between multiple fragments. The total time consumption of sobEDA is only about twice that of conventional DFT single-point calculation for the entire system. This work also proposes a variant of the sobEDA method named sobEDAw, which is designed specifically for decomposing weak interaction energies. Through a proper combination of DFT correlation energy and dispersion correction term, sobEDAw gives a ratio between dispersion energy and electrostatic energy that is highly consistent with the symmetry-adapted perturbation theory, which is quite popular and robust in studying weak interactions but expensive. We present a shell script sobEDA.sh to implement the methods proposed in this work based on the very popular Gaussian quantum chemistry program and Multiwfn wavefunction analysis code. Via the script, theoretical chemists can use the sobEDA and sobEDAw methods very conveniently in their study. Through a series of examples, the rationality of the new methods and their implementation are verified, and their great practical values in the study of various chemical systems are demonstrated.

Effect of solvents on intra- and inter-molecular interactions of oligothiophenes.

Oligothiophenes have long been used as model compounds to understand the chemistry of polythiophenes. Herein, we have some quantum chemical calculations and intra- and inter-molecular interaction calculations of a series of oligothiophenes such as terthiophene, quintetthiophene, sevensthiophene, terthiophene-terthiophene, terthiophene-water, terthiophene-methanol, and terthiophene-chloroform performed by time-dependent density functional theory (TD-DFT), density functional theory (DFT), and Multiwfn: a multifunctional wavefunction analyzer. The UV-vis spectra, HOMO-LUMO energies, NBO analysis, MEP, molecular structures, and electronic properties were computed using DFT/TD-DFT at the level of B3LYP/6-31+ G (d,p) and described. The nature of molecular interactions between terthiophene and solvents like water, methanol, and chloroform were also investigated using non-covalent interaction index (NCI), reduced density gradient (RDG), localized orbital locator (LOL), and electron localization function (ELF) topological analyses. Besides, Fukui functions and energy of population density-of-states were computed using the same method. The calculation results show that there are some changes in the terthiophene with the addition of solvent to the medium. DFT calculations were performed using the Gaussian 09 software and GaussView 5.0 visulation program. Multiwfn software is used to calculate the reduced density gradient (RDG) scatterplots, non-covalent interactions (NCI), ELF, LOL, Fukui analysis, and energy of population density-of-states of oligothiophenes.