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In a series of recent papers, we investigated the effect of dynamical electron correlation on the potential energy curves and spectroscopic constants of several diatomic molecules, including the simple diatomic hydrides (AH) and the more complex diatomic fluorides (AF) and homonuclear diatomic molecules (A 2 ) with A = B-F (AF) or A = C-F (A 2 ), respectively. Our goal was to understand the dependence of the dynamical electron correlation energy, E DEC , on the internuclear distance, R , and quantify how dynamical electron correlation influences the spectroscopic constants ( D e , R e , and ω e ) of these molecules. At large R , we found that the magnitude of E DEC ( R ) had a simple dependence on R, with E DEC ( R ) increasing nearly exponentially with decreasing R ) could be correlated with changes in the underlying spin-coupled generalized valence bond wave function, either in the orbitals or the spin-coupling coefficients. In the current paper, we extend these studies to higher main group elements, comparing the effects of R continued to decrease, there were significant variations in E DEC ( R ). These variations led to differing changes in the predicted spectroscopic constants of the molecules. In many molecules, the changes in E DEC ( R ) could be correlated with changes in the underlying spin-coupled generalized valence bond wave function, either in the orbitals or the spin-coupling coefficients. In the current paper, we extend these studies to higher main group elements, comparing the effects of E DEC ( R ) on P 2 and As 2 versus N 2 , and on Cl 2 and Br 2 versus F 2 . We find that there are significant differences between the effects of dynamical electron correlation on the molecules in the first and subsequent rows of the periodic table.

The space group of a crystal describes the symmetry and periodic arrangement of its structure. As the fundamental element in the structure, it plays a vital role in determining the physical and chemical properties of crystals. The investigation of crystal space group information allows for the prediction of material properties, thereby providing guidance for material design and synthesis to enhance their performance or functionality. Currently prevalent first-principles-based computational methods exhibit good accuracy, but they rely heavily on computing resources, greatly limiting the efficiency of material screening. In this paper, our study is oriented toward the prediction the spatial group of crystals, and an algorithm named Rewc, based on graph neural networks (GNNs) is proposed. This algorithm encodes all atoms and the interactions between atoms in the crystal as features by combining Floyd algorithm and k -hop message passing and employs multilayer convolutional networks to extract connections between k layers. This allows for the automatic learning of more representative atomic vector representations through iterations of feature information for each atom and its neighbors. Experimental results demonstrate that the Rewc framework exhibits reliable accuracy and good generalization capabilities in predicting the crystal structure compared to previous GNN methods.

We present a deorbitalization of the recent simplified, regularized Tao-Mo exchange functional ( J. Chem. Phys. 2023, 159, 214102) that is faithful to the parent functional. That is a major gain relative to our earlier deorbitalization which did poorly on molecular heats of formation ( J. Chem. Phys. 2023, 159, 214103). The improvement arises from augmentation of the Mejía-Rodríguez and Trickey deorbitalization strategy ( Phys. Rev. A 2017, 96, 052512) to use a smoothed replacement for the reduced density Laplacian (conventionally denoted q ) obtained from that Laplacian itself. The augmentation also rationalizes the improvement obtained from the cutoff of q < 0 that was poorly understood at the time of the previous paper. The new scheme yields deorbitalized chemical region indicators that are much closer to those from the parent, orbital-dependent functional than were obtainable from the previous deorbitalization. It also replicates the good 3d elemental magnetization of the parent functional reasonably well.

Direct methanol fuel cells (DMFCs) have attracted increasing attention as a very promising and important energy source. In this paper, density functional theory (DFT) is used to study the structure and O-H fracture mechanism of methanol adsorption on Pt n Cu 4- n (111) ( n = 1, 2, 3) binary metal catalyst surfaces under different coverages. By comparing the adsorption energy and dehydrogenation energy barriers of methanol, it is found that the adsorption strength and dehydrogenation energy barriers of methanol on Pt and Cu sites decreased with increasing coverage. At the same Pt and Cu ratio, methanol is more easily adsorbed on Cu sites. When Pt/Cu = 3:1 and 1:3, the PtCu binary catalyst has a significant impact on the energy barrier of breaking the O-H bond in methanol with the increase of coverage. Especially when Pt/Cu = 1:3 and the coverage is 1/4 ML, the energy barriers of O-H bond breaking in methanol on Pt and Cu sites are 0.63 and 0.61 eV, respectively, which are lower than that on pure Pt. It means that the Cu sites played a very important role in reducing the O-H fracture energy barrier of methanol. When Pt/Cu = 1:1, the change in the dehydrogenation energy barrier of methanol on Pt sites and Cu sites is not significant, indicating that the coverage has little effect on it.

Regions of nuclear-configuration space away from the Franck-Condon geometry can prove problematic for some electronic structure methods, given the propensity of such regions to possess conical intersections, i.e., (highly connected) points of degeneracy between potential energy surfaces. With the likelihood (perhaps even inevitability) for nonadiabatic dynamics simulations to explore molecular geometries in close proximity to conical intersections, it is vital that the performance of electronic structure methods is routinely examined in this context. In a recent paper [Taylor, J. T. J. Chem. Phys. 2023, 159, 214115.], the ability of linear-response time-dependent density functional theory within the adiabatic approximation (AA LR-TDDFT) to provide a proper description of conical intersections, in terms of their topology and topography, was investigated, with particular attention paid to conical intersections between two excited electronic states. For the same prototypical molecules, protonated formaldimine and pyrazine, we herein consider whether AA LR-TDDFT can correctly reproduce the topological phase accumulated by the adiabatic electronic wave function upon traversing a closed path around an excited-to-excited state conical intersection despite not using the appropriate quadratic-response nonadiabatic coupling vectors. Equally, we probe the ability of the ground-to-excited state intersection ring exhibited by AA LR-TDDFT in protonated formaldimine to give rise to a similar topological phase in spite of its incorrect dimensionality.

Methyl esters are an important component of combustion and atmospheric systems. Reaction with the OH radical plays an important role in the removal of the simplest methyl ester, methyl formate (MF, CH 3 OCHO). In this paper, the overall rate coefficients for the reactions of OH and OD with MF isotopologues, studied under pseudo-first-order conditions, are reported using two different laser flash photolysis systems with the decay of OH monitored by laser-induced fluorescence. The room-temperature rate coefficient for OH + MF, (1.95 ± 0.34) × 10 -13 cm 3 molecule -1 s -1 , is in good agreement with the literature. The rate coefficient exhibits curved Arrhenius behavior, and our results bridge the gap between previous low-temperature and shock tube studies. In combination with the literature, the rate coefficient for the reaction of OH with MF between 230 and 1400 K can be parametrized as k OH+MF = (3.2 × 10 -13 ) × (T/300 K) 2.3 × exp(-141.4 K/ T ) cm 3 molecule -1 s -1 with an overall estimated uncertainty of ∼30%. The reactions of OD with MF isotopologues show a small enhancement (inverse secondary isotope effect) compared to the respective OH reactions. The reaction of OH/OD with MF shows a normal primary isotope effect, a decrease in the rate coefficient when MF is partially or fully deuterated. Experimental studies have been supported by ab initio calculations at the CCSD(T)-F12/aug-cc-pVTZ//M06-2 X /6-31+G** level of theory. The calculated, zero-point-corrected, barrier heights for abstraction at the methyl and formate sites are 1.3 and 6.0 kJ mol -1 , respectively, and the ab initio predictions of kinetic isotope effects are in agreement with experiment. Fitting the experimental isotopologue data refines these barriers to 0.9 ± 0.6 and 4.1 ± 0.9 kJ mol -1 . The branching ratio is approximately 50:50 at 300 K. Between 300 and 500 K, abstraction via the higher-energy, higher-entropy formate transition state becomes more favored (60:40). However, experiment and calculations suggest that as the temperature increases further, with higher energy, less constrained conformers of the methyl transition state become more significant. The implications of the experimental and theoretical results for the mechanisms of MF atmospheric oxidation and low-temperature combustion are discussed.

In a strong field regime, exploring the molecular photodissociation process and revealing the underlying reaction mechanism remain challenging tasks due to the dramatic changes of molecular potentials caused by the applied fields. In this paper, we investigate the strong field photodissociation dynamics of D 2 + in a synthesized VUV + IR (266 + 800 nm) two-color laser field by solving the three-dimensional time-dependent Schrödinger equation. We show that the Aharonov-Bohm-like quantum interference in the photofragment angular distribution can be controlled by varying the ellipticity of the VUV light. We demonstrate that the interference phenomenon originates from the geometric phase accumulation of the nuclear wave function when it undergoes cyclic evolution on light-induced potential energy surfaces. This work has implications for the control of chemical reactions of a small molecular system through the geometric phase.

The abundance of XIII group element compounds in science and industry together with their electron-deficient character gives rise to their influence on properties of the systems they interact with. This paper is an attempt to assess the strength, nature, and effect of formation of a triel bond on acidity. A wide set of Brønsted acids among others comprising hydrocarbons, halogen hydrides, and amines bonded with B, Al, and Ga trifluorides forming HX/TF 3 was selected for the research. Various computational approaches (e.g., MP2, GFN2-xTB, SAPT2 + 3(CCD)δ MP2 , quantum theory of atoms in molecules analysis, and density overlap regions indicator) are used to describe the triel-bonded systems. Among other things, it was found that the electrostatics may not be the dominant contribution to the triel binding in some cases. Additionally, it was established that even weak Brønsted acids such as C 2 H 2 or H 2 may be superacidic if bonded to a Lewis acid (TF 3 ) that is strong enough. The calculations indicate a significant covalent character of some of the studied HX/TF 3 triel-bonded systems. Moreover, the effect of solvation of HX with TF 3 as well as that of the reverse process on the acidity of the resulting system is thoroughly described.

Inorganic molecular crystal (IMC) is a trending class of materials in which structural units comprise molecular cages or clusters bonded via van der Waal forces. The structure-property relationship in IMCs is less known due to the unusual assembly of molecular clusters in these materials. In this paper, the density functional theory-calculated electronic transport properties of the molecular clusters of antimony oxide (Sb 4 O 6 ), phosphorus triselenide (P 4 Se 3 ), and phosphorus trioxide (P 4 O 6 ) are described in detail. The calculated values of highest occupied molecular orbital-lowest unoccupied molecular orbital gaps appeared as 5.487, 2.296, and 4.425 eV for Sb 4 O 6 , P 4 Se 3 , and P 4 O 6 , respectively. The work was carried out to explore the charge transport mechanism in IMCs in order to disclose their potential in practical applications. The calculations involved charge-transfer integral based on Marcus theory to compute the electronic coupling ( V ), reorganization energies (λ), and hopping rate ( k ) in the structures. The hopping rate for Sb 4 O 6 , P 4 Se 3 , and P 4 O 6 is found as 8.49 × 10 -12 , 1.28 × 10 -14 , and 2.51 × 10 -20 s -1 , respectively. The transport properties of Sb 4 O 6 are found better, which predicts the application of the relevant IMC for device grade applications. The findings of this study are important for future application of the IMCs in electronic and optoelectronic applications.

The new versions of the Pisa composite scheme introduced in the present paper are based on the careful selection of different quantum chemical models for energies, geometries, and vibrational frequencies, with the aim of maximizing the accuracy of the overall description while retaining a reasonable cost for all the steps. In particular, the computation of accurate electronic energies has been further improved introducing more reliable complete basis set extrapolations and estimation of core-valence correlation, together with improved basis sets for third-row atoms. Furthermore, the reduced-cost frozen natural orbital (FNO) model has been introduced and validated for large molecules. Accurate molecular structures can be obtained avoiding complete basis set extrapolation and evaluating core-valence correlation at the MP2 level. Unfortunately, analytical gradients are not available for the FNO version of the model. Therefore, for large molecules, an accurate reduced-cost alternative is offered by evaluation of valence contributions with a double-hybrid functional in conjunction with the same MP2 contribution for core-valence correlation or by means of a one-parameter approximation. The same double-hybrid functional and basis set are employed to evaluate zero-point energies and partition functions. After the validation of the new models for small systems, a panel of molecular bricks of life has been used to analyze their performances for problems of current fundamental or technological interest. The fully black-box implementation of the computational workflow paves the way toward the accurate yet not prohibitively expensive study of medium- to large-sized molecules also by experimentally oriented researchers.

The reaction of H + Cl 2 → HCl + Cl plays a crucial role in various fields. However, no previous study has investigated this reaction using accurate quantum mechanical methods. In this paper, we construct a global potential energy surface (PES) using the neural network method with more than 20,000 ab initio energies obtained by the MRCI-F12+Q method with the aug-cc-pV5Z basis and extrapolated to the complete basis set limit. The spin-orbit coupling of the Cl atom has been considered in the PES. With this new PES, product state-resolved quantum dynamics calculations for the H + Cl 2 ( v 0 = 0, j 0 = 0-2) → HCl + Cl reaction was carried out. Numerical results show that the initial rotational excitation of the Cl 2 has negligible effects on the reactivity. Product state-resolved integral cross sections (ICS) and rate constants reveal that the HCl is most favorably produced in its v ' = 2 vibrational state. The calculated product vibrational state-resolved and total reaction rate constants suggest that the new global PES is accurate enough, as compared with the available experimental measurements.

Locating the lowest energy conformer is crucial for the accurate computation of equilibrium properties of molecular systems. This paper examines the performance of efficient low-cost methods in terms of the alignment and relative energies of their energy minima against the benchmark revDSD-PBEP86-D4/def2-TZVPP//MP2/cc-pVTZ potential energy surface. The low-cost methods considered include GFN-FF, GFN2-xTB, DFTB3, HF-3c, B97-3c, PBEh-3c, and r 2 SCAN-3c composite methods against a diverse test set of 20 compounds including alkanes, perfluoroalkyl molecules, peptides, open-shell radicals, and Zn(II) complexes of varying sizes. The "3c" composite methods are generally more accurate, but are at least 2-3 orders of magnitude more expensive than tight-binding methods which have energy minima that align well with the benchmark potential energy surface. The findings of this paper were further exploited to introduce a simple strategy involving Grimme's CENSO energy-sorting algorithm that resulted in up to an order of magnitude reduction in computational time for locating the lowest energy conformer on the revDSD-PBEP86-D4/def2-TZVPP//MP2/cc-pVTZ surface.

Nanopore field-effect transistor (NP-FET) devices hold great promise as sensitive single-molecule sensors, which provide CMOS-based on-chip readout and are also highly amenable to parallelization. A plethora of applications will therefore benefit from NP-FET technology, such as large-scale molecular analysis (e.g., proteomics). Due to its potential for parallelization, the NP-FET looks particularly well-suited for the high-throughput readout of DNA-based barcodes. However, to date, no study exists that unravels the bit-rate capabilities of NP-FET devices. In this paper, we design DNA-based barcodes by labeling a piece of double-stranded DNA with dumbbell-like DNA structures. We explore the impact of both the size of the dumbbells and their spacing on achievable bit-rates. The conformational fluctuations of this DNA-origami, as observed by molecular dynamics (MD) simulation, are accounted for when selecting label sizes. An experimentally informed 3D continuum nanofluidic-nanoelectronic device model subsequently predicts both the ionic current and FET signals. We present a barcode design for a conceptually generic NP-FET, with a 14 nm diameter pore, operating in conditions corresponding to experiments. By adjusting the spacing between the labels to half the length of the pore, we show that a bit-rate of 78 kbit·s -1 is achievable. This lies well beyond the state-of-the-art of ≈40 kbit·s -1 , with significant headroom for further optimizations. We also highlight the advantages of NP-FET readout based on the larger signal size and sinusoidal signal shape.

Recent work in combustion and atmospheric chemistry has revealed cases in which diastereomers must be distinguished to accurately model a reacting flow. This paper presents an open-source framework for introducing such stereoisomer resolution into a kinetic mechanism. We detail our definitions and algorithms for labeling and enumerating the stereoisomers of a molecule and then generalize our system to describe the transition state (TS) of a reaction. This allows for the stereospecific enumeration of reactants and products while accounting for "fleeting" stereochemistry that is unique to the TS. We also present the AutoMech Chemical Identifier (AMChI), an InChI-like string identifier that accounts for stereocenters omitted by InChI. This identifier is extended to describe the TSs of reactions, providing a universal lookup key for specific reaction channels. The final piece of our methodology is an analytic formula to remove redundancy from a stereoresolved mechanism when its enantiomers exist as a racemic mixture, making it as compact as possible while fully accounting for the differences between diastereomers. In applying our methodology to two subsets of the NUIGMech1.1 mechanism, we find that our approach reduces the extra species added for large-fuel oxidation from 2231 (133%, full expansion) to 694 (41%, nonredundant expansion). We also find that for pyrolysis more than a quarter of the species in the expanded mechanism cannot be properly described by an InChI string, requiring an AMChI string to communicate their identity. Finally, we find that roughly one-quarter of the large-fuel oxidation reactions and one-third of the pyrolysis reactions include fleeting TS stereochemistry, which may have relevant effects on their kinetics.

The uniform semiclassical expression for the energy-dependent transmission probability through a barrier has been a staple of reaction rate theory for almost 90 years. Yet, when using the classical Euclidean action, the transmission probability is identical to 1/2 when the energy equals the barrier height since the Euclidean action vanishes at this energy. This result is generally incorrect. It also leads to an inaccurate estimate of the leading order term in an ℏ expansion of the thermal transmission coefficient. The central result of this paper is that adding an 2 n expansion of the thermal transmission coefficient. The central result of this paper is that adding an ℏ 2 dependent correction to the uniform semiclassical expression, whether as a constant action or as a shift in the energy scale, not only corrects this inaccuracy but also leads to a theory that is more accurate than the previous one for almost any energy. Shifting the energy scale is a generalization of the vibrational perturbation theory 2 (VPT2) and is much more accurate than the "standard" VPT2 theory, especially when the potential is asymmetric. Shifting the action by a constant is a generalization of a result obtained by Yasumori and Fueki (YF) only for the Eckart barrier. The resulting modified VPT2 and YF semiclassical theories are applied to the symmetric and asymmetric Eckart barrier, a Gaussian barrier, and a tanh barrier. The one-dimensional theories are also generalized to many-dimensional systems. Their effect on the thermal instanton theory is discussed.

The typical hydrogen atom plus halogen molecule reaction H + Cl 2 → HCl + Cl has implications across many fields. In this paper, product state-resolved quantum dynamics calculations for the vibrationally excited reaction H + Cl 2 ( v 0 = 1-3, j 0 = 0) → HCl + Cl were conducted using the time-dependent wave packet method on a newly developed accurate potential energy surface. Numerical results indicate that the initial vibrational excitation of Cl 2 does enhance the reactivity for this early barrier reaction, although less than the enhancement of the translational energy. The calculated product vibrational state-resolved integral cross sections and rate constants reveal that the product vibrational state distribution and the initial vibrational state of Cl 2 are highly correlated. The thermal rate constant in the temperature range from 100 to 1000 K was given and is found to be in reasonable agreement with the experimental measurements.

The Hofmann-Löffler-Freytag (HLF) reaction serves as a late-stage functionalization technique for generating pyrrolidine heterocyclic ring systems. Contemporary HLF protocols utilize in situ halogenated sulfonamides as precursors in the radical-mediated rearrangement cycle. Despite its well-established reaction mechanism, experiments toward the detection of radical intermediates using EPR techniques have only recently been attempted. However, the obtained spectra lack the distinct features of the N-centered radicals expected for the employed reactants. This paper presents phenylbutylnitrone spin-trapped C-centered and N-centered radicals, generated via light irradiation from N-halogen-tosyl-sulfonamide derivatives and detected using EPR spectroscopy. NMR spectroscopy and DFT calculations are used to explain the observed regioselectivity of the HLF reaction.

Hexagonal boron nitride (hBN) has attracted significant attention as a two-dimensional (2D) material due to its unique structure and properties. In this paper, we investigated the gas-phase reactions between B 2 H 6 and NH 3 and the reaction pathways potentially leading to the synthesis of hBN by using ReaxFF-based reactive molecular dynamics (MD) simulations. From the hundreds of chemical reaction pathways observed in these MD simulations, we extracted a highly reduced chemical kinetic model to describe the gas-phase mixture evolution in chemical vapor deposition of hBN using B 2 H 6 and NH 3 as precursors. The intent is to integrate this chemical model into future computational fluid dynamics (CFD) simulations of actual hBN deposition testing and production reactors to provide enhanced insights for experimental synthesis processes and reactor optimization. The chemical model of this study will serve as a stepping stone for large-scale simulations.

The design and development of novel and efficient donor-π-acceptor (D-π-A) type conjugated systems has attracted substantial interest in the field of organic electronics owing to their intriguing properties. In this paper, we have designed seven new and efficient D-π-A type conjugated systems (M1-M7) by a variety of π-linkers with triphenylamine (TPA) as the electron donor and diphenyldiketopyrrolopyrrole (DPP) as the electron acceptor using density functional theory (DFT) formalism for organic solar cells (OSCs). The π-linker has been substituted between the donor and acceptor for efficient electron transfer. Here, our primary focus is on narrowing the highest occupied molecular orbital-lowest unoccupied molecular orbital gaps, electronic transition, charge transfer rate, reorganization energies, and the theoretical power conversion efficiencies (PCEs). Our study reveals that the designed compounds exhibit excellent charge transfer rates. The absorption properties of the compounds have been examined using the time-dependent density functional theory (TD-DFT) method. The TD-DFT study shows that compound M2 possesses the highest absorption maxima with a maximum bathochromic shift. For a better understanding of the electron transport process of our designed compounds, we have designed donor/acceptor (D/A) blends, and each of the developed blends (FREA/M1-M7) can encourage charge carrier separation. According to the photovoltaic performance of the D/A blends, compound FREA-M2, which has a theoretical PCE of 16.53%, is the most appealing choice for use in OSCs. We expect that by thoroughly examining the relationship between structure, characteristics, and performance, this work will serve as a roadmap for future research and development of TPA-DPP-based photovoltaic materials.

In this paper, we present a new finding, the basis electronic activity (BEA) of molecular systems; it corresponds to the significant, although nonreactive, vibrationally induced electronic activity that takes place in any molecular system. Although the molecule's BEA is composed of an equal number of local contributions as the vibrational degrees of freedom, our results indicate that only stretching modes contribute to it. To account for this electronic activity, a new descriptor, the bond electronic flux (BEF), is introduced. The BEF combined with the force constant of the potential well hosting the electronic activity gives rise to the effective bond reactivity index (EBR), which turns out to be the first density functional theory-based descriptor that simultaneously accounts for structural and electronic effects. Besides quantifying the bond reactivity, EBR provides a basis to compare the reactivities of bonds inserted in different chemical environments and paves the way for the exertion of selective control to enhance or inhibit their reactivities. The new concepts formulated in this paper and the associated computational tools are illustrated with characterization of the BEA of a set of representative molecules. In all cases, the BEFs follow the same linear pattern, whose slopes indicate the intensity of the electronic activity and quantify the reactivity of chemical bonds.

In this paper, we demonstrate two topological properties of crossing seams, that is, the sets of points in the N -dimensional space of nuclear coordinates where two electronic eigenstates are degenerate. We shall examine the typical case of states of the same spin with accidental degeneracies, whereby the crossing seam is of dimension N - 2. The first property we demonstrate is that a crossing seam has no boundary, therefore, it must either extend asymptotically to infinite values of one or more coordinates or wrap on itself. The second property is that two (or more) crossing seams can intersect each other but in such a way that neither of them ends at the intersection. When N = 3, the crossing seam is a line in a 3D space; this is so in triatomic molecules but also in reduced dimensionality treatments of larger polyatomics. The above-mentioned rules then mean that the crossing seam is a line of infinite length or a closed loop and can split into three branches but not in two. The example of the first two excited 1 A ' states of H 2 Cl + illustrates these rules and shows their usefulness for computational search and characterization of crossing seams.

We recently introduced the particle-breaking restricted Hartree-Fock (PBRHF) model, a mean-field approach to address the fractional charging of molecules when they interact with an electronic environment. In this paper, we present an extension of the model referred to as particle-breaking unrestricted Hartree-Fock (PBUHF). The unrestricted formulation contains odd-electron states necessary for a realistic description of fractional charging. Within the PBUHF parametrization, we use two-body operators as they yield convenient operator transformations. However, two-body operators can change only the particle number by two. Therefore, we include noninteracting zero-energy bath orbitals to generate a linear combination of even and odd electron states. Depending on whether the occupied or virtual orbitals of a molecule interact with the environment, the average number of electrons is either decreased or increased. Without interaction, PBUHF reduces to the unrestricted Hartree-Fock wave function.

Recently, there has been debate about using a pseudo-second-order model in adsorption kinetics and its ability to fit experimental data, especially at the initial stages. This paper introduces a generalized fractional kinetic model obtained via a fractional reaction-diffusion equation with a time-dependent reaction rate. This model is presented as a dependable approach to understanding chemical adsorption kinetics. It offers insights into the adsorbate history and extends classical kinetic models, such as pseudo-first-order and pseudo-second-order models. The generalized fractional kinetic model accounts for memory effects with long-range interactions, heterogeneity, and nonequilibrium dynamics, leading to more accurate predictions of adsorption rates, capacities, and equilibrium values. As an applied context, we use the fractional kinetic model to analyze experimental data on the adsorption of anionic acid yellow-17 and cationic brilliant green dyes in single and binary systems. The fractional kinetic model is employed to fit the data by incorporating waiting times into the adsorption process and correlating macroscopic properties, such as the pH, with adsorption dynamics.

Polyimide (PI), due to its exceptional performance, is commonly utilized in spacecraft. However, when such polymers are used in spacecraft navigating low Earth orbit, they are exposed to atomic oxygen (AO) that can cause the polymer to decompose. A protective coating method is a more effective way to safeguard the polymer from erosion caused by AO. This study employs the molecular dynamics simulation based on the reaction force field to investigate the protective effects of various coatings, including polydimethylsiloxane (PDMS), graphene (Gr), polytetrafluoroethylene (PTFE), and the (0 0 1), (0 1 1), and (1 1 1) surfaces of SiO 2 . The results indicate that the protective performance of the (0 1 1) surface is superior to that of the (0 0 1) and (1 1 1) surfaces. Moreover, protective coatings are classified into three categories based on different protective mechanisms: rebound, absorption, and sacrificial. The protective effectiveness of coatings depends on their anti-AO performance and ability to combine with the substrate. Gr displays exceptional anti-AO properties and can effectively shield the substrate from AO erosion. Silicone-based coatings have a superior ability to adhere to PI substrates, and PDMS is an excellent choice for protective coatings. This paper offers guidance for the protective coating method of PIs against AO erosion.

Hamiltonian matrices typically contain many elements that are negligibly small compared to the diagonal elements, even with methods to prune the underlying basis. Because for general potentials the calculation of H -matrix elements is a major part of the computational effort to obtain eigenvalues and eigenfunctions of the Hamiltonian, there is strong motivation to investigate locating these negligible elements without calculating them or at least avoid calculating them. We recently demonstrated an effective means to "learn" negligible elements using machine learning classification ( J. Chem. Phys. , 159, 071101). Here we present a simple, new method to avoid calculating them by using a cut-off value for the absolute difference in the quantum numbers for the bra and ket. This method is demonstrated for many of the same case studies as were used in the paper above, namely for realistic 2023 , 159, 071101). Here we present a simple, new method to avoid calculating them by using a cut-off value for the absolute difference in the quantum numbers for the bra and ket. This method is demonstrated for many of the same case studies as were used in the paper above, namely for realistic H -matrices of H 2 O, the vinyl radical, C 2 H 3 , and glycine, C 2 H 5 NO 2 . The new method is compared to the recently reported machine learning approach. In addition, we point out an important synergy between the two methods.

In this paper, we investigate the effects of solvation on the solar energy storage properties of bicyclooctadiene/tetracyclooctane (BOD/TCO) photoswitches. The solvent effects on the thermochemical and optical properties are studied in cyclohexane, toluene, dichloromethane, ethanol, acetonitrile, and a vacuum using density functional theory and coupled cluster theory. Our results show that the energy storage capacity of the BOD/TCO system increases as the solvent polarity increases, and the change is more significant with an unsubstituted system. The energy storage capacity of the substituted system is not dependent on the polarity of the solvent. As the solvent polarity increases, the absorption peaks shift away from each other and the absorption intensities increase. Overall, the solvents improve the performance of the optical properties and the energy storage capacities of the BOD/TCO molecular solar thermal systems.

The SiS + cation is considered a potential astromolecule, yet there is limited documentation regarding its spectroscopic properties and spectral line intensities. In this paper, the potential energy curves, dipole moments, and transition dipole moments of the SiS + cation are calculated using the icMRCI + Q method. By solving the one-dimensional Schrödinger equation for the nucleus, we have obtained spectroscopic constants for both the ground state and 11 low-lying excited states. Utilizing the vibrational transition energy levels of these 12 bound states, we calculated the partition function for the SiS + cation over the temperature range of 300-10,000 K. Upon deriving the partition function and Einstein coefficients, we have computed the spectral line intensities for the X 2 Π state, the A 2 Σ + state, and the X 2 Π ↔ A 2 Σ + transition at 300 and 3000 K for Δν = 0,1,2. At T = 300 K, the intensity of the X 2 Π state 1-0 band reaches its maximum, while at T = 3000 K, the intensity of the A 2 Σ + state 0-0 band reaches its maximum. The spectral line intensities of the X 2 Π ↔ A 2 Σ + transition, on the other hand, are relatively small, with the overall intensity being smaller compared to the spectral line intensities of the X 2 Π and A 2 Σ + states by about 10 -6 .