Vertical Potentials Research Articles

Mechanism of the distinct toxicity level of imidacloprid and thiacloprid against honey bees: An in silico study based on cytochrome P450 9Q3

The honey bee, Apis mellifera, shows variation in sensitivity to imidacloprid and thiacloprid, which does not reside at the target site but rather in the rapidly oxidative metabolism mediated by P450s (such as a single P450, CYP9Q3). An in silico study was conducted to investigate the various metabolism of imidacloprid and thiacloprid. The binding potency of thiacloprid was stronger and a stable π-π interaction with Phe121 and the N–H⋯N hydrogen bond with Asn214 are found in the CYP9Q3-thiacloprid system but absent in imidacloprid, which might affect the potential metabolic activity. Moreover, the values of highest occupied molecular orbit (HOMO) energy and the vertical ionization potential (IP) of two compounds demonstrated that thiacloprid is more likely to oxidation. The findings revealed the probable binding modes of imidacloprid and thiacloprid with CYP9Q3 and might facilitate future design of the low bee toxicity neonicotinoid insecticides.

Light-Emitting Properties of Pyrimidine-5-Carbonitrile Derivatives: a Theoretical Calculation

In this study, 4,6-Di (9H-carbazol-9-yl) pyrimidine-5-carbonitrile (C1), 4,6-bis (3,6-di-tert-butyl-9H-carbazol-9-yl) pyrimidine-5-carbonitrile (C2), 4,6-bis (3,6-dimethoxy-9H-carbazol-9-yl) pyrimidine-5-carbonitrile (C3) compounds were optimized at the B3LYP/6-31G(d) level. Energy densities of frontier molecular orbitals were investigated with molecular properties. Vertical ionization potentials (IPv), adiabatic ionization potential (IPa) (in eV), vertical electron affinity (EAv), adiabatic electron affinity (EAa), the hole reorganization energy (h )and electron reorganization energy (e ) were calculated (in eV) for C1, C2 and C3 compounds. e values of the C1 and C3 compounds are 0.29 and 0.30 eV and the h value is 0.18 and 0.20 eV, respectively. It can be said that the C1 and C3 compounds are not suitable as an electron bearing layers (ETL) material since its e values are greater than 0.276 eV and that its h value is less than 0.290 eV, so they are a suitable material for the hole bearing layers (HTL). The C2 compound is suitable for both ETL and HTL materials.

Study on charge transport properties and photoelectric properties of two series of 2,5-di(pyridine-2-yl)thiophene derivatives

In order to adjust the charge transfer performance and photoelectric characteristics of 2,5-di(pyridine-2-yl)thiophene (DPT) infrastructure, two series of 2,5-di(2-quinolyl)thiophene (DQT) and 2,5-di(3-isoquinolyl)thiophene (DIQT) derivatives were designed by introducing benzene, naphthalene, anthracene, tetrabenzene and pentabenzene at both ends of the molecule to extend the conjugated length. The geometric structure, orbital energy, absorption spectrum, emission spectrum and recombination energy of the designed molecules were studied by quantum chemical calculation method. The results show that the decrease of LUMO energy level and the increase of HOMO energy level can reduce Egap, which leads to the red shift of absorption wavelength and fluorescence emission wavelength; The vertical ionization potential is reduced and the vertical electron affinity is improved, thereby reducing the hole and electron injection barrier; The hole/electron recombination energy is reduced and the charge transfer ability of molecules is improved.

Insights into the electronic structure and stability of TiMgn (n = 1–12) clusters: Validation of electron counting rule

The present study reports the investigation of the electronic structure and stability of TiMgn (n = 1–12) nanoclusters in the framework of the linear combination of atomic orbital density functional theory (DFT) together with a spin-polarized generalized gradient approximation (GGA). We have calculated different thermodynamic and chemical parameters, such as binding energy (BE), embedding energy (EE), fragmentation energy (FE), HOMO-LUMO gap, vertical ionization potential (VIP), vertical electron affinity (VEA), etc. during the growth process of the cluster to understand their stability. From the study, the TiMg8 cluster comes out to be the most stable cluster. Further, the positive charge (Mulliken charge) on the Ti in TiMg8 cluster indicates that the Mg8-cage behaves as an electron acceptor during hybridization with the Ti. The absence of any reactive site (obtained from NBO), minimum Mg-Ti bond length, and negative NICS in TiMg8 ground state cluster support it as a globally stable cluster. Low ELF index value revealing the non-reactivity of the TiMg8 cluster. Finally, orbital analysis shows that TiMg8 clusters follow closed-cell electronic orbital sequence 1S21P61D102S2 and satisfy the 20-electron counting rule. IR and Raman spectrum calculations are also presented to understand the vibrational nature of the clusters.

Structural, electronic, thermodynamic and optical properties of SnlSemSn clusters: A DFT study

• DFT study of electronic, thermodynamic and optical properties of SnlSemSn clusters. • Band gap energy of Sn l Se m S n clusters lie in the semiconducting range (1.035–3.463 eV). • Sn 1 Se 1 S 2 is found to be the most reactive cluster. • Absorption spectra can be tailored by varying thecomposition of atoms in clusters. Density Functional Theory (DFT) calculations are performed to investigate the structural, electronic, thermodynamic, and optical properties of Sn l Se m S n clusters with the variation in the number of Sn, Se, and S atoms using B3LYP/321-G ∗ level of theory. We have obtained 23 optimized clusters and their calculated properties are dependent on the size, geometry, and structure of clusters. We observed that Sn 1 Se 1 S 2 is found to be highly reactive owing to its largest values of electronegativity, vertical ionization potential, vertical electron affinity with the least values of binding energy and band gap energy. The least reactive cluster is Sn 1 Se 1 S 8 with the maximum values of band gap and hardness. The band gap energies of all clusters lie in the semiconducting range (1.035 eV–3.463 eV). The optical absorption is observed in ultraviolet and visible regions. The theoretically computed absorption spectrum for excited states is compared experimentally confirming their applications in optoelectronics.

DFT study of transition metals doped calix-4-pyrrole with excellent electronic and non-linear optical properties

Herein a detailed comparative study on the transition metal doped calix-4-pyrrole was carried out to determine the optical, electronic, and non-linear optical (NLO) properties, as well as to synthesize some thermodynamically stable complexes. All the computational work was accomplished using density functional theory (DFT). The optical and chemical properties of Sc[CPM1]Sc, Ti[CPM1]Sc, Sc[CPM1]Ti, and Ti[CPM1]Ti were seen to be superior to the un-doped cage. Doping of transition metals inside and outside the cage increased the diffused excess electrons, as a result lowering the energy gap (from 4.01 to 2.15 eV). Due to these excess electrons and lower excitation energy, noteworthy increasement took place in the polarizability and hyperpolarizability of all doped structures. The minimum energy gap (2.15 eV) and largest first hyperpolarizability (16360 a.u) was observed for Sc[CPM1]Sc. Non-covalent interaction (NCI) analysis illustrated that the intermolecular forces are the major cause of interaction between the cage and dopants. It was also indicated from the density of state (DOS) and frontier molecular orbital (FMO) diagrams that the transition metals significantly raised the distribution of charge density in the structures under study, especially in Sc[CPM1]Sc, while the capability to transfer charges was revealed from transition density matrix (TDM) graphs. Natural bond orbital (NBO) charge analysis revealed that transfer of charges occurred from the dopants towards the surface. Calculated values of interaction energy, binding energy, and vertical ionization potential confirmed the thermo-dynamical stability of the molecules. Time-dependent DFT measures were conducted to evaluate all the necessary transitions and absorption analysis. Consequently, all the calculated parameters praised the capability of our designed molecules in the field of electronics and non-linear optics.

Effects of Molecular Structure on Organic Contaminants' Degradation Efficiency and Dominant ROS in the Advanced Oxidation Process with Multiple ROS.

In this study, the previously overlooked effects of contaminants' molecular structure on their degradation efficiencies and dominant reactive oxygen species (ROS) in advanced oxidation processes (AOPs) are investigated with a peroxymonosulfate (PMS) activation system selected as the typical AOP system. Averagely, degradation efficiencies of 19 contaminants are discrepant in the CoCaAl-LDO/PMS system with production of SO4•-, •OH, and 1O2. Density functional theory calculations indicated that compounds with high EHOMO, low-energy gap (ΔE = ELUMO - EHOMO), and low vertical ionization potential are more vulnerable to be attacked. Further analysis disclosed that the dominant ROS was the same one when treating similar types of contaminants, namely SO4•-, 1O2, 1O2, and •OH for the degradation of CBZ-like compounds, SAs, bisphenol, and triazine compounds, respectively. This phenomenon may be caused by the contaminants' structures especially the commonly shared or basic parent structures which can affect their effective reaction time and second-order rate constants with ROS, thus influencing the contribution of each ROS during its degradation. Overall, the new insights gained in this study provide a basis for designing more effective AOPs to improve their practical application in wastewater treatment.

The structures and properties of Mon (n = 2[formula omitted]15) cluster

The stable isomers of Mon (n=2∼15) are determined by using genetic algorithm combined with DFT calculations. Some new ground-state structures are found. The 3D structure firstly appears for Mo4 and the distorted pyramid or prism isomers are energy favored for n = 4∼9, while icosahedron-like or cage-like structures are dominant for n = 10∼15. Mo3, Mo5, Mo7, Mo8, Mo11 and Mo13 are magic number clusters. There are small magnetic moments and vertical electron affinity but large vertical ionization potential for Mon. The electronic structure analysis indicates that there form strong Mo-Mo covalent bonds, which are also delocalization to a certain extent due to the 4d and 5s orbital hybridization. The IR and UV–vis spectra are acquired and the particularly large hyper polarizability of Mo9 also suggests that it can be used as a nonlinear optical material.

Structures, electronic and thermodynamic properties of NiB2n (n = 7–11) and their anions: A theoretical study

AbstractParticle Swarm Optimization (CALYPSO) searching method and density functional theory (DFT) were used to study structures, electronic, and thermodynamic properties of NiB2n0/− (n = 7–11) clusters at the TPSSh/6‐311 + G(d) level of theory. Results found that the lowest energy structures possess a Ni atom‐centered double ring tubular boron structures, NiB180/− except. Relative stabilities were analyzed via computing their vertical ionization potentials (VIP), vertical electronic affinity (VEA), adiabatic electronic affinity (AEA), HOMO‐LUMO gaps and hardness. The infrared spectra, Raman spectra and photoelectron spectra were computationally simulated to facilitate their experimental characterizations. At last, aromatic properties (nucleus independent chemical shift and anisotropy of the current induced density) and thermodynamic properties (enthalpy and entropy) with temperature were discussed in detail for studied systems.

Hydrocarbon Oxidation Depth: H2O2/Cu2Cl4·2DMG/CH3CN System

The oxidation of hydrocarbons of different structures under the same conditions is an important stage in the study of the chemical properties of both the hydrocarbons themselves and the oxidation catalysts. In a 50% H2O2/Cu2Cl4·2DMG/CH3CN system, where DMG is dimethylglyoxime (Butane-2,3-dione dioxime), at 50 °C under the same or similar conditions, we oxidized eleven RH hydrocarbons of different structures: mono-, bi- and tri-cyclic, framework and aromatic. To compare the composition of the oxidation products of these hydrocarbons, we introduced a new quantitative characteristic, “distributive oxidation depth D(O), %” and showed the effectiveness of its application. The adiabatic ionization potentials (AIP) and the vertical ionization potentials (VIP) of the molecules of eleven oxidized and related hydrocarbons were calculated using the DFT method in the B3LYP/TZVPP level of theory for comparison with experimental values and correlation with D(O). The same calculations of AIP were made for the molecules of the oxidant, solvent, DMG, related compounds and products. It is shown that component X, which determines the mechanism of oxidation of hydrocarbons RH with AIP(Exp) ≥ AIP(X) = 8.55 ± 0.03 eV, is a trans-DMG molecule. Firstly theoretically estimated experimental values of AIP(trans-DMG) = 8.53 eV and AIP(cis-DMG) = 8.27 eV.

Hybrid functionals with local range separation: Accurate atomization energies and reaction barrier heights.

Range-separated hybrid approximations to the exchange-correlation density functional mix exact and semi-local exchange in a position-dependent manner. In their conventional form, the range separation is controlled by a constant parameter. Turning this constant into a density functional leads to a locally space-dependent range-separation function and thus a more powerful and flexible range-separation approach. In this work, we explore the self-consistent implementation of a local range-separated hybrid, taking into account a one-electron self-interaction correction and the behavior under uniform density scaling. We discuss different forms of the local range-separation function that depend on the electron density, its gradient, and the kinetic energy density. For test sets of atomization energies, reaction barrier heights, and total energies of atoms, we demonstrate that our best model is a clear improvement over common global range-separated hybrid functionals and can compete with density functionals that contain multiple empirical parameters. Promising results for equilibrium bond lengths, harmonic vibrational frequencies, and vertical ionization potentials further underline the potential and flexibility of our approach.

Vertical ionization potential benchmarks from Koopmans prediction of Kohn–Sham theory with long-range corrected (LC) functional* *In memory of Enrico Clementi.

The Kohn–Sham density functional theory (KS-DFT) with the long-range corrected (LC) functional is applied to the benchmark dataset of 401 valence ionization potentials (IPs) of 63 small molecules of Chong, Gritsenko and Baerends (the CGB set). The vertical IP of the CGB set are estimated as negative orbital energies within the context of the Koopmans’ prediction using the LCgau-core range-separation scheme in combination with PW86–PW91 exchange–correlation functional. The range separation parameter μ of the functional is tuned to minimize the error of the negative HOMO orbital energy from experimental IP. The results are compared with literature data, including ab initio IP variant of the equation-of-motion coupled cluster theory with singles and doubles (IP-EOM-CCSD), the negative orbital energies calculated by KS-DFT with the statistical averaging of orbital potential, and those with the QTP family of functionals. The optimally tuned LC functional performs better than other functionals for the estimation of valence level IP. The mean absolute deviations (MAD) from experiment and from IP-EOM-CCSD are 0.31 eV (1.77%) and 0.25 eV (1.46%), respectively. LCgau-core performs quite well even with fixed μ (not system-dependent). A μ value around 0.36 bohr−1 gives MAD of 0.40 eV (2.42%) and 0.33 eV (1.96%) relative to experiment and IP-EOM-CCSD, respectively. The LCgau-core-PW86–PW91 functional is an efficient alternative to IP-EOM-CCSD and it is reasonably accurate for outer valence orbitals. We have also examined its application to core ionization energies of C(1s), N(1s), O(1s) and F(1s). The C(1s) core ionization energies are reproduced reasonably [MAD of 46 cases is 0.76 eV (0.26%)] but N(1s), O(1s) and F(1s) core ionization energies are predicted less accurately.

Cover Feature: Photoionization, Structures, and Energetics of Na‐Doped Formic Acid–Water Clusters (ChemPhysChem 5/2022)

The Cover Feature shows the natural difference orbital profiles of the first electronic excited states in the UV wavelength range of Na⋅⋅⋅HCOOH⋅⋅⋅(H2O)n clusters. The existence of these Rydberg–type electronic transitions could explain the cluster ionization at laser energy lower than their vertical ionization potential, enabling the correct data interpretation on acid-water cluster formation. More information can be found in the Research Article by Tonia M. Di Palma and co-workers.

Ab initio DFT simulation of electronic and magnetic properties of Tin+1 and FeTin clusters.

We report a computational investigation of the electronic and magnetic properties of neutral Tin+1 and FeTin (n = 1-10) clusters using ab initio calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA). The best structures for Tin+1 and FeTin clusters are planar for size n < 5, while from n = 5, they showed a compact three-dimensional cage structure. For the best structures of the FeTin clusters, the Fe atoms favor the peripheral position with the highest coordination with the neighboring Ti atoms. The evolution as a function of the size of the average binding energies (Eb/atom) and HOMO-LUMO gaps of Tin+1 and FeTin (n = 1-10) clusters are studied. The stability results show that the Tin+1 clusters have relatively higher stability than the FeTin cluster with the same size. In addition, the vertical ionization potentials and electron affinities, chemical hardness, and atomic magnetic moment of Tin+1 and FeTin (n = 1-10) clusters are also investigated.

Vertical ionization potential benchmark for unitary coupled-cluster and algebraic-diagrammatic construction methods.

The performance of several methods for the calculation of vertical ionization potentials (IPs) or, more generally, electron-detachment energies based on unitary coupled-cluster (UCC) theory and the algebraic-diagrammatic construction (ADC) scheme is evaluated with respect to benchmark data computed at the level of equation-of-motion coupled-cluster theory, including single, double, and triple excitations (IP-EOM-CCSDT). Based on a statistical evaluation of about 200 electron-detached states of 41 molecules, the second-order methods IP-ADC(2) and IP-UCC2 show modest accuracies with IP-EOM-CCSDT as reference, exposing a mean signed error and a standard deviation of the error of -0.54 ± 0.50 and -0.49 ± 0.54eV, respectively, accompanied by a mean absolute error (MAE) of 0.61 and 0.58eV, respectively. The strict third-order IP-ADC method demonstrates an accuracy of 0.26 ± 0.35eV (MAE = 0.35eV), while the IP-UCC3 method is slightly more accurate with 0.24 ± 0.26eV (MAE = 0.29eV). Employing the static self-energy computed using the Dyson expansion method (DEM) improves the IP-ADC(3) performance to 0.27 ± 0.28eV, with the mean absolute error of this method being 0.32eV. However, employing the simpler improved fourth-order scheme Σ(4+) for the static self-energy provides almost identical results as the DEM. Based on the quality of the present benchmark results, it therefore appears not necessary to use the computationally more demanding DEM.

Density functional theory study of BiRun (n = 3–20) clusters: Structural, electronic and adsorptive properties for hazardous gases

The geometric structures and electronic properties as well as adsorption of some harmful gas molecules for BiRun (n = 3–20) clusters are investigated using the generalized gradient approximation of density functional theory (DFT/GGA). The clusters largely show low symmetries (e.g., Cs) and generally exhibit the polyhedral structures with Bi atom at the vertices, while BiRu6, BiRu11, BiRu12 and BiRu17 clusters have the highest C5V symmetry and stability. Interestingly, the structure of BiRun (n = 3–20) clusters shows growth property, i.e., construction of BiRun (n = 3–20) by addition one Ru atom to BiRun−1, and Run and Run−1 clusters also have similar geometrical structures. BiRu5 and BiRu12 are found to exhibit relatively higher thermodynamic stability from the second-order energy difference. BiRu12 and BiRu6 can display the highest chemical stability and activity in view of the largest and smallest energy gap Eg, respectively. Vertical ionization potential (VIP) and vertical electron affinity (VEA) show the decreasing and increasing trends with n, respectively. As for the adsorption properties of these clusters for harmful gas molecules, excellent and good adsorption performances are found for CO and NH3 molecules adsorbed on BiRu14 and BiRu20, whereas NO and H2S molecules exhibit poor adsorption properties on these clusters. The study of this work would be helpful to construct and characterize the electronic properties of BiRun (n = 3–20) clusters and to explore their potential adsorption performances and the prospect to act as efficient sensors for the harmful gases.

Experimental and Theoretical Study of Gamma Radiolysis and Dose Rate Effect of o-Cresol Formaldehyde Epoxy Composites.

Gamma radiolysis behaviors and mechanisms of silica-filled o-cresol formaldehyde epoxy are studied at 2.20 × 10-5 to 1.95 × 10-1 Gy/s. The radiolysis-induced changes in chemical structures do not severely affect its thermostability. The slightly deteriorated mechanical strength at temperature exceeding 100 °C is accompanied by the declining glass transition temperature (from 185.9 to 172.2 °C) and enhanced damping ability. The gas yields of hydrogen, methane, and carbon dioxide manifest a remarkable dose rate effect. Based on the Schwarzschild law, their yields at an extremely low dose rate are accurately predicted by the established master curves. Besides, the latent radiolysis of gas products and postradiation effect are found with caution. The radiation-caused residual spin species are proved to be composed of silica defects and a phenoxy-type free radical with a tert-butyl group, according to the experimental results, theoretical calculations, and spectra simulations. The lower vertical ionization potential (7.6 eV) and adiabatic ionization potential (7.1 eV) are primarily due to the ionization of the benzene ring moiety with the tert-butyl group, which is likely to suffer from radiolysis. The calculated bond dissociation energy (260.8-563.5 kJ/mol) of the typical chemical bonds of epoxy is consistent with its radiolytic vulnerability and degradation mechanisms.

Calculation of vertical and adiabatic ionization potentials for some benzaldehydes using hybrid DFT, multilevel G3B3 and MP2 methods

The adiabatic ionization potential (AIP) and vertical ionization potential (VIP) for eight benzaldehydes were calculated using DFT (B3LYP, CAM-B3LYP and ωB97XD), MP2, G3B3 and CBS-QB3 methods. Basis set dependence was checked using four different basis sets 6-311G(d,p), 6-31+G(d,p), 6-311++G(2df,2p) and cc-pVTZ. Computed results were compared with the experimental data. Error metrics and statistical tools were used to validate the methods tested. Results showed an excellent agreement between the computed results and the experimental ones. Nature of the substituted groups and solvent effect on AIP values were investigated. Changes in the geometrical structures of cationic species were compared with neutral ones.

STABLE STRUCTURES, MAGNETIC AND ELECTRONIC PROPERTIES OF SMALL BIMETALLIC PtCo NANOALLOYS UP 5 ATOMS: A DFT STUDY

In bulk regime size, Co presents an HCP phase and Pt has an FCC phase, both present interesting properties of technological relevance. Co is ferromagnetic and Pt is a good catalyst. Nanoalloying allows us to play with the size and the chemical composition to achieve new properties and functionalities that do not exist at the bulk regime. In this work, we studied the interaction between PtCo atoms and how to affect the chemical order, the magnetic properties and electronic properties of these binary nanoalloys up 5 atoms. Our results show that Co atoms prefer to be localized at sites with the highest coordination in nanoalloys with 5 atoms, in PtCo clusters with 4 atoms, we found planar geometries as the stable ones. All the nanoalloys have a favorable atom mixing; the bimetallic clusters considered in this study show magnetic behavior and present a ferromagnetic-like order where the value of the total magnetization depends on the number of Co atoms of the cluster. We have considered the vertical ionization potential to determine the donation of electrons and the capture of electrons is studied through the electronic affinity and these are related to the chemical hardness which is an index of catalytic activity. This study was done into the DFT scheme as implemented in the SIESTA code using a generalized gradient approximation.

Actively Searching: Inverse Design of Novel Molecules with Simultaneously Optimized Properties.

Combining quantum chemistry characterizations with generative machine learning models has the potential to accelerate molecular discovery. In this paradigm, quantum chemistry acts as a relatively cost-effective oracle for evaluating the properties of particular molecules, while generative models provide a means of sampling chemical space based on learned structure-function relationships. For practical applications, multiple potentially orthogonal properties must be optimized in tandem during a discovery workflow. This carries additional difficulties associated with the specificity of the targets and the ability for the model to reconcile all properties simultaneously. Here, we demonstrate an active learning approach to improve the performance of multi-target generative chemical models. We first demonstrate the effectiveness of a set of baseline models trained on single property prediction tasks in generating novel compounds (i.e., not present in the training data) with various property targets, including both interpolative and extrapolative generation scenarios. For property ranges where accurate targeting proves difficult, the novel compounds suggested by the model are characterized using quantum chemistry and the new molecules closest to expressing the desired properties are fed back into the generative model for additional training. This gradually improves the generative models' understanding of targeted areas of chemical space and shifts the distribution of the generated compounds toward the targeted values. We then demonstrate the effectiveness of this active learning approach in generating compounds with multiple chemical constraints, including vertical ionization potential, electron affinity, and dipole moment targets, and validate the results at the ωB97X-D3/def2-TZVP level. This method requires no modifications to extant generative approaches, but rather utilizes their inherent generative and predictive aspects for self-refinement, and can be applied to situations where any number of properties with varying degrees of correlation must be optimized simultaneously.