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Moisture is an important factor affecting the insulation properties of transformers. Due to the limitations of macroscopic experimental methods, the diffusion of water at oil-paper interface cannot be accurately measured. Therefore, molecular dynamics method was used in this work to establish oil-paper layer model of 105 atoms. Through jointly analysing the aggregation degree, diffusion coefficient, free volume as well as radial distribution function of water molecules, the diffusion mechanism of water molecules at oil-paper interface was studied. The results show that when the initial water content in paper was high, water molecules would accumulate at oil-paper interface to form the local high-water region during heating. The polarisation of the electric field strengthened the hydrogen bonding interaction between water molecules and increased the probability of occurrence of the high-water region. Meanwhile, electric field reduced the free volume and diffusion coefficient of water molecules and rendered its diffusion coefficient anisotropic. What’s more, when the electric field was combined with the temperature field, the electric field played a leading role in the diffusion of water molecules while the temperature field was less affected. Diffusion coefficients of water molecules at different temperatures from molecular dynamics simulations were well consistent with experimental results, which verified the rationality of the model. [ABSTRACT FROM AUTHOR]

The electron correlation effects covered by density functional theory (DFT) can be assessed qualitatively by comparing DFT densities ρ(r) with suitable reference densities obtained with wavefunction theory (WFT) methods that cover typical electron correlation effects. The analysis of difference densities ρ(DFT)-ρ(WFT) reveals that LDA and GGA exchange (X) functionals mimic non-dynamic correlation effects in an unspecified way. It is shown that these long range correlation effects are caused by the self-interaction error (SIE) of standard X functionals. Self-interaction corrected (SIC) DFT exchange gives, similar to exact exchange, for the bonding region a delocalized exchange hole, and does not cover any correlation effects. Hence, the exchange SIE is responsible for the fact that DFT densities often resemble MP4 or MP2 densities. The correlation functional changes X-only DFT densities in a manner observed when higher order coupling effects between lower order N-electron correlation effects are included. Hybrid functionals lead to changes in the density similar to those caused by SICDFT, which simply reflects the fact that hybrid functionals have been developed to cover part of the SIE and its long range correlation effects in a balanced manner. In the case of spin-unrestricted DFT (UDFT), non-dynamic electron correlation effects enter the calculation both via the X functional and via the wavefunction, which may cause a double-counting of correlation effects. The use of UDFT in the form of permuted orbital and broken-symmetry DFT (PO-UDFT, BS-UDFT) can lead to reasonable descriptions of multireference systems provided certain conditions are fulfilled. More reliable, however, is a combination of DFT and WFT methods, which makes the routine description of multireference systems possible. The development of such methods implies a separation of dynamic and non-dynamic correlation effects. Strategies for accomplishing this goal are discussed in general and tested in practice for CAS (complete active space)-DFT. [ABSTRACT FROM AUTHOR]

It is difficult to overestimate how much quantum chemistry owes to Frank Boys. He was a pioneer, an individualist, a dedicated scientist and a great man. [ABSTRACT FROM AUTHOR]

Lutosław Wolniewicz, one of prominent quantum chemists, known for his seminal works on the structure and spectra of the hydrogen molecule and its isotopomers, passed away in December 2020. This paper presents his life and works. [ABSTRACT FROM AUTHOR]

The article discusses the research conducted by Thomas Mellor, the winner of the Molecular Physics Longuet-Higgins Early Career Researcher Prize 2022. Mellor's paper focuses on the development of molecular frames for a symmetry-adapted rotational basis set. The research aims to improve the accuracy and computational efficiency of calculating molecular absorption spectra by minimizing rotational-vibrational coupling. Mellor explores the challenges of defining molecular rotations and the impact of symmetry on computational load and classification of molecular states. The paper presents new frames for specific molecules and proposes a more systematic approach to the problem. The research has practical implications for rotational-vibrational calculations and the use of different coordinate systems. Mellor hopes that his work will inspire further exploration and the development of frames for other classes of molecules. [Extracted from the article]

Reverse degree-based topological indices (RDTIs) are applied to analyze the structural properties of molecules such as gamma graphyne and armchair graphyne nanoribbons. RDTIs provide valuable information about the connectivity patterns of atoms within a molecule, aiding in understanding its chemical and physical properties. For gamma graphyne and armchair graphyne nanoribbons, RDTIs would involve calculating the contributions from various atom pairs based on the degree differences between them. These indices consider the reverse order in which degrees are subtracted. RDTIs capture important aspects of molecular structure, including branching, degree distribution, and connectivity. Using RDTIs, one can assess the complexity, stability, and other characteristics of gamma graphyne and armchair graphyne nanoribbons. This paper focus on two structures made from hexagonal honeycomb graphite lattices, like gamma graphyne, and armchair graphyne nanoribbons. The methodology used in this study is First and second reverse Gourava indices, hyper first and second reverse Gourava indices, reverse multiplicative sum connectivity Gourava index, and reverse multiplicative product connectivity Gourava. Furthermore, these indices play a vital role in quantitative structure–property relationships and offer insights into the behaviour and reactivity of these unique molecular structures. Further research and computational analysis of RDTIs will deepen our understanding of these fascinating carbon-based materials. [ABSTRACT FROM AUTHOR]

In this paper, we studied the quantum dynamics of the TiC, NiC, and CuLi diatomic molecules interacting with the Varshni-Eckart potential (VEP) model in topological defects geometry associated with cosmic string under the influence of magnetic and Aharonov-Bohm (AB) flux fields. We employ the Greene-Aldrich approximation scheme in the centrifugal term and determine the approximate eigenvalue solution using the Nikiforov-Uvarov-Functional Analysis (NUFA) method. The numerical energy spectra for topological defects geometry and external fields with this potential are determined. Subsequently, we applied the eigenvalue solution to various cases of the potential model and obtained their analytical solutions. When compared to Minkowski flat space results, the presence of topological defects and external fields eliminates degeneracy and shifts the energy spectra of the diatomic molecules. [ABSTRACT FROM AUTHOR]

This document is a profile of Gabriel M. Silva, the winner of the Molecular Physics early career researcher prize in 2022. Silva's winning article focuses on the Debye-Hückel equations, which are fundamental equations for the thermodynamics of electrolyte solutions. The paper explores different pathways to derive these equations, questioning approximations and clarifying ongoing issues. The research has practical implications for the electrolyte thermodynamics field, as understanding the derivations of these equations is crucial. Silva also discusses the future development of the research area, including advancements in electrolyte equations of state and a focus on aspects such as ion-pairing models and ion-solvent interactions. Silva expresses gratitude for winning the prize and discusses their inspiration for getting involved in this research. [Extracted from the article]

As a metalloid with unique properties, single crystal germanium is widely used in semiconductors, infrared optics, and other fields. To ensure the processing accuracy of single-crystal germanium, it is necessary to optimise the selection of parameters during processing. This paper uses molecular dynamics methods to study the cutting process of single-crystal germanium with the cutting depth and cutting speed as parameters and uses nanoindentation method to test the mechanical properties of the processed single-crystal germanium surface. The study found that with the increase of cutting depth, the cutting force and cutting heat increased significantly, the depth of the deformed layer increased significantly, and the stiffness of single-crystal germanium decreased significantly; with the increase of cutting speed, there was no built-up edge Influence, the cutting force is reduced, and more cutting heat is generated, and the depth of the deformation layer is higher, and the HCP structure increases, but the cutting speed has no obvious relationship with the mechanical properties of the machined surface. [ABSTRACT FROM AUTHOR]

This paper adopted the 2D periodic boundary-condition (PBC) density functional theory (DFT) to examine the adsorption of CH3Br, CH3Cl, and CH3F halomethanes into not only bare boron phosphide (BP) nanosheets but also gallium- and aluminium-doped ones. Geometric optimisation was applied to all the structures at the B3LYP/6-311+G (d) level of theory. Moreover, the CAM-B3LYP/6-311+G(d), ωB97X-D3, and M06-2X levels of theory were implemented to calculate the single point energy. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were carried out, evaluating the donor-acceptor interactions, partial natural charge, and Wiberg bond index (WBI). The adsorption energy values demonstrated that the gallium-doped BP had the highest adsorptive capability, while the lowest adsorption occurred in the bare BP. However, the adsorption of CH3Cl, with much smaller adsorption energy, was maximised in the aluminium-doped BP and minimised in the bare BP. Furthermore, CH3Br and CH3Cl showed the highest and lowest tendencies to be adsorbed onto the nanosheet surfaces, respectively. Gallium- and aluminium-doped BP structures appear to be efficient and effective in the development of new solid-state sensors of halomethanes. [ABSTRACT FROM AUTHOR]

The molecular graph theory is one of the essential tools for developing and constructing molecular structure. In particular, using topological invariant, which is a numerical descriptor of molecular graph, has become widespread in predicting physical properties. Topological indices provide knowledge about the overall form of molecular graphs, particularly various degree-based topological indices. This research paper focuses on the first and second Zagreb index and their coindices for the line graph of a transition metal-organic network. The network, denoted by L (TM − TCNB) , comprises the transition metals Ti, V, Cr, Fe, Co, Ni, Cu or Zn, and the TCNB ligand. The line graph of a network is a graph that represents the connections between the edges of the original network. The Zagreb indices are widely used to describe the molecular graph's shape and structure. The paper highlights the importance of these indices in modelling the chemical properties of the transition metal-organic network. The study results show that the Zagreb indices and their coindices strongly correlate with several physical characteristics, for instance the boiling points, melting points, and density of the network. [ABSTRACT FROM AUTHOR]

Calls for papers and advance information for the Fifth Liblice Conference on the Statistical Mechanics of Liquids from June 7 to 12, 1998 in Czech Republic. Scientific and organizing committee; Information regarding conference; Plenary speakers.

This paper examines the satisfaction of the principle of corresponding states (PCS) on thepressure–density–temperature relation and the binary diffusion coefficient of hydrogen/oxygen mixture modelled as binary Lennard–Jones (LJ) fluid especially in a supercritical region. The hydrogen/oxygen mixture properties were computed by molecular dynamics simulation and compared with simulation results for a nitrogen/oxygen mixture as well as while using the Peng–Robinson (PR) equation of state (EOS) for both mixture types and a mono-component LJ-EOS. The Fuller–Schettler–Giddings model with the PR-EOS and Takahashi's EOS were used for binary diffusion coefficient comparison. The pseudocritical point concept of a fluid mixture was applied for PCS reduction and PCS satisfaction was conducted over a wide temperature range above the pseudocritical pressure with changing hydrogen molar fraction. PCS satisfaction for hydrogen/oxygen mixture properties was confirmed at reduced temperature of 1.5 or above. At reduced temperature of 1.0 or below, the hydrogen/oxygen mixture properties disagree with those of the comparison mixture because phase separation occurs. We conclude that the properties of hydrogen/oxygen mixtures can be estimated using the pseudocritical point concept and the investigated EOSs based on the PCS in the supercritical region at reduced temperature of1.5 or above. [ABSTRACT FROM AUTHOR]

Precision spectroscopy of simple, calculable molecules has become an important tool to compare experiments with theory in an effort to test our understanding of the fundamental laws of physics. For this purpose, we have measured the E F 1 Σ g + (v ′ = 0 , N ′ = 0) ← X 1 Σ g + (v ″ = 0 , N ″ = 0) transition frequency of molecular deuterium ( D 2 ) with unprecedented accuracy. We use Ramsey-Comb spectroscopy at deep-ultraviolet wavelengths (201 nm) with a two-photon, Doppler-free interrogation scheme. The resulting transition frequency is f = 2 , 981 , 779 , 227 , 578 (19) kHz. The 1-σ uncertainty of 19 kHz represents an improvement of more than two orders of magnitude compared to the best previous measurement. In this paper, we give an extensive description of our methods and the experimental apparatus that we employed. Particular attention is given to aspects that we recently improved, such as the frequency comb laser system, the method of signal recording, and the cryogenic D 2 molecular beam apparatus. In combination with future measurements of the ionisation energy of the EF state, our measurement paves the way for an improved determination of the ground state ionisation and dissociation energy of molecular deuterium. [ABSTRACT FROM AUTHOR]

As known, electron vacuum polarisation by nuclear Coulomb field produces the Uehling potential with the range ℏ / 2 m e c. Similarly, neutrino vacuum polarisation by the Z boson field produces a long-range potential ∼ G F 2 / r 5 with a very large range ℏ / 2 m ν c. Measurements of macroscopic effects produced by the potential G eff 2 / r 5 give limits on the effective interaction constant G eff which exceed Fermi constant G F by many orders of magnitude, while limits from the spectroscopy of simple atomic systems are approaching the Standard Model predictions. In this paper, we consider limits on G eff from hydrogen, muonium, positronium, deuteron and molecular hydrogen. Constraints are also obtained on fifth force parameterised by Yukawa-type potential mediated by a scalar particle. [ABSTRACT FROM AUTHOR]

Phenylenes belong to a special class of conjugated hydrocarbons composed of a special arrangement of hexagons and squares. In the phenylene structure, every square is adjacent to a pair of hexagons, and any two hexagons are not adjacent. If in the structure of phenylene only two squares are adjacent to every hexagon, then it is called a phenylene chain. In this paper, we compute the expected values of the first and second Gourava index, the first and second redefined Zagreb index, and the Hyper-Zagreb index of random phenylene chains. Furthermore, a comparison between the expected values of the computed indices among the classes of random phenylene chains has been investigated. [ABSTRACT FROM AUTHOR]

Graph theory has found significant use in chemistry, especially in modelling chemical structures. A molecular graph can be represented by a graph where atoms represent vertices and links between these atoms are called edges. Each molecular structure has its own physical properties, such as boiling point, melting point, density, molecular mass, entropy, etc. A topological invariant of a molecular structure is a descriptor that is correlated to certain chemical and biological actions of the chemical compounds. In this paper, we studied the structure of oxide networks, triangular silicate networks, dominating oxide networks and dominating silicate networks in connection to some additive degree-based topological indices. Specifically, the ranking among these networks is also determined with the help of certain multi-criteria decision-making techniques (MCDM). In the end, regression and correlation analyses between their chemical properties and topological indices has been observed. [ABSTRACT FROM AUTHOR]

Organic light-emitting diodes (OLEDs) have been widely used in various fields such as sensors. In this article, we designed six novel heterocyclic Ir(III) complexes: (CFM)2Ir(acac) (named 1 in this paper), (TTIQ)2Ir(acac) (named 2), (CFM)2Ir(tmd) (named 3), (TTIQ)2Ir(tmd) (named 4), (CFM)2Ir(pic) (named 5) and (TTIQ)2Ir(pic) (named 6). The six iridium (III) complexes were calculated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). We studied the bands of the lowest-lying absorptions and lowest energy emissions of complexes 1–6. In addition, we also explored their spectral properties, frontier Molecular Orbital theory(FMO) and spin-orbital coupling value(SOC). Where acac is represented as pentane-2, 4-dione; tmd as 2,2,6,6-tetramethylheptane-3,5-dione; pic as pyridine-2-carboxylate; TTIQ as 1- { thieno[3,2-b]thiophen-2-yl } isoquinoline; CFM as 2-(4-fluorobrobenyl)-4-methylpyridine. A series of heteroleptic cyclometalated Ir (III) complexes, which are used for OLED application, were investigated by DFT and TD-DFT method. The frontier molecular orbital character and charge transfer character shown that they have the advantages of low efficiency roll-off properties, which is a 'stumbling block' in the process of OLED solid-lighting's development. Namely, means the materials will play an important role in the journey development of OLED. [ABSTRACT FROM AUTHOR]

Regarding Euclidean geometry, introduced the Sombor index and its various types. In graph theory, it is the sum of all pairs of neighbouring vertices. New varieties of Sombor indices are introduced using geometrical interpretation. In this paper, we reviewed recently created Sombor indices for gamma-sheet of boron clusters. In particular, Euclidean geometry introduced the first area-based Sombor index. Perimeters are used to construct the third and fifth Sombor indices, while in terms of angular orientation, the second, fourth, and sixth Sombor indices are determined. Sombor indices can be useful in the analysis of chemical networks because they provide a way to quantify the complexity of the network based on the distances between its constituent molecules. They can be used, for example, to compare the structures of different chemical networks, or to identify regions of high or low connectivity within a network. Degree-based Sombor indices have been used in the analysis of various types of chemical networks, including protein-protein interaction networks, metabolic networks, and gene co-expression networks, among others. They can provide insights into the structure and function of these networks and can be used for tasks such as network clustering, identification of key nodes, and prediction of network behaviour. All the versions of Sombor indices are depend on the degree or valency of bond. First, finding out the degree type of the entire network and then the edge type is also essential to compute the Sombor index, once both types are determined, put the values in the derived formulas, and one can have imported results of Sombor indices. [ABSTRACT FROM AUTHOR]

In 1986, I was very fortunate to receive a Guggenheim Fellowship that I used to spend a semester at Harvard in the group of W. N. Lipscomb, known to all as the "Colonel" because of his honorary Kentucky Colonel status. Our final effort, "Applications of post-Hartree Fock Methods: A Tutorial", in Reviews in Computational Chemistry, 1994, offered a mini-textbook on the subject John's many, notable contributions after leaving my group should be told by the authors of the papers in this special issue. Just as he was exceptionally productive while still a graduate student, he published 10 quality papers in 1991, including his first foray into the NO SB 3 sb molecule, a long-term interest of John's. [Extracted from the article]

Molecular simulation data of the vapour–liquid equilibria (VLE) published in the period 2005–2016 and listed in the Web-of-Science collection have been scrutinised and their correctness examined using the recently proposed exact compressibility factor criterion [I. Nezbeda, J. Chem. Eng. Data 61, 3964 (2016)]. It turns out that a large number of the examined data are very inaccurate, if not completely wrong, and this is illustrated by several examples. This problem goes, unfortunately, unnoticed and the data are further used by other researchers. The finding goes hand-in-hand with the becoming practice of ignoring the common etiquette of presenting (pseudo)experimental data, i.e. to provide sufficient information both on technical details and on data post-simulation processing which could enable anyone their independent check and further reliable use. Moreover, the problem of the correctness of published data does not concern only VLE data but any simulation results and these cases along with potential reasons are therefore also briefly discussed. An appeal is therefore made both to the community of simulators and users to examine data using available tools before publishing or using them. Similarly, an appeal is made also to reviewers to insist that the submitted papers with simulation data do contain all necessary details. [ABSTRACT FROM AUTHOR]

This paper is the second of two back-to-back works, whose goal was to generate a more accurate linelist for the 5.8 µm absorption band of HNO3. Here, we report improved line positions and intensities in the ν2 cold band which is the main band in this region. For this, we recorded four high-resolution Fourier transform spectra for the ν2 band, centered at 1709.567 cm−1, under different experimental conditions. Using these spectra, a new extended line position analysis was performed for the ν2 band, leading to more accurate line positions. In parallel, individual line intensities were measured. It appears that, although the ν2 band is mainly of B-type, it also possesses a (very) weak A-type component that cannot be ignored. Overall, the line intensities in this new database are about 8% weaker than those quoted presently in the HITRAN () or GEISA () databases. Our final linelist for HNO3 at 5.8 µm is provided as a supplement to this paper. It includes lines from the ν2 band together with those of the ν2+ν9−ν9, ν2+ν6−ν6, and ν2+ν7−ν7 associated hot bands that were generated during the first part of this study, described in the companion paper. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the convergence properties of density matrix renormalisation group (DMRG) calculations for vertical electronic excitations performed on three bimolecular complexes motivated by Szalay's recent benchmark results [JCTC. 2020;16:7]. Besides the high-level coupled-cluster reference spectrum, the extrapolated truncation-free DMRG results are compared against several alternative solutions based on multireference configuration interaction and coupled-cluster theories. By taking advantage of the error cancellation effects, which are inherent in the state-averaged computational scheme, we demonstrate that the extrapolated solution based on only low bond-dimensional DMRG data could already provide quantitative predictions even for large active spaces. We also show that orbital optimisation improves further the accuracy of the DMRG results which systematically approach the excitation energies of coupled cluster single-double-triple at similar computational costs. [ABSTRACT FROM AUTHOR]

A-value is conventionally defined as the ring flip Gibbs energy of chair conformers in monosubstituted cyclohexanes. It is well accepted in organic chemistry as one of the proxies of steric hindrance of a substituent group with respect to hydrogen. In this paper, the ring flip energy of mono– and dihalogenated cyclohexanes was investigated by high-level quantum chemical methods. Satisfactory agreements between calculated values and published experimental values from NMR were established before extending the concept to ring flip energies of polyhalogenated cyclohexanes. We assessed the qualitative and quantitative accuracy of prediction of ring flip energies by A-values in two models: a simple and intuitive model based on linear combinations of A-values and a proposed extension of this model to include geminal substituent interactions. The simple model results in poor predictions of ring flip energy in polyhalogenated cyclohexanes, and the extended model provides only slight improvement. Our data suggests that simple linear combination of traditional or extended A-values may not be appropriate for the energy prediction of systems in this study. [ABSTRACT FROM AUTHOR]

This paper reviews some of the graph theory-based methods that were recently developed in our group for post-processing molecular dynamics trajectories. We show that the use of algorithmic graph theory not only provides a direct and fast methodology to identify conformers that are sampled over time, but it also allows to follow in time the interconversions between the conformers through graphs of transitions, also provides statistical characterisations, that would otherwise be hard to obtain. Examples for a gas phase peptide and for the more complex inhomogeneous charged air–liquid water interface are presented in order to demonstrate the power of topological 2D-graphs and their versatility and transferability. [ABSTRACT FROM AUTHOR]

In this paper, we obtain analytical vibrational partition function with recent energy spectrum of the deformed hyperbolic barrier potential. We derive different thermodynamic properties for the RbH , NaK , KRb , NI , 7 Li 2 and N 2 diatomic molecules. In addition, we obtain the total molar entropy for the two last molecules. Our results are in excellent agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this paper, we study the quantum motions of the non-relativistic particles under the influence of the flux field in the background of a point-like global monopole with Kratzer plus generalised Yukawa potential. The solutions of the quantum system under consideration are obtained using the parametric Nikiforov–Uvarov method by employing the Greene–Aldrich approximation scheme in the centrifugal and reciprocal terms that appear in the radial equation. Afterwards, we use another approximation called the Taylor series expansion up to the first order in the exponential terms and solve the radial equation analytically using the confluent hypergeometric function. It is shown that the topological defect of a point-like global monopole influences the eigenvalue solutions of the non-relativistic particles and gets modified by this defect compared to the flat space result with this superposed potential. We also show that the energy eigenvalue of the particles depends on the quantum flux field and thus gets shifted. Finally, we compare the eigenvalue solutions obtain for these two approximations scheme used here and show graphically that the results are different in these schemes. [ABSTRACT FROM AUTHOR]

In this paper, we test the ability of a recently proposed effective frequency theory, viz. the generalised Feynman–Kleinert effective frequency theory (GFK), for calculating the Wigner transform of the thermalised flux operator needed in reaction rate computations based on the classical Wigner model. We consider one-dimensional symmetric and asymmetric barriers at both high and low temperatures. The reaction rates obtained from the GFK theory are found to be close to the results obtained using the accurate Wigner function. The reaction rates obtained from the classical Wigner model are approximate since they are based on classical trajectories. We therefore also present a new version of the so-called effective quantum force method, that improves the classical Wigner rates. This new implementation utilises as input matrix elements of the thermalised flux operator obtained from the GFK theory. We find a significant improvement compared to the classical Wigner reaction rates. Possible extensions to multi-dimensional systems are discussed. [ABSTRACT FROM AUTHOR]

The reaction mechanisms for OH-initiated oxidation of trans-β-ocimene (TBO) in the atmosphere have been investigated at the CCSD(T)/6-31 + G(d)//BH&HLYP/6-311++G(d,p) levels of theory. Classical transition state theory (CTST) is used to obtain the rate constants of initial reaction pathways over the temperature range of 220–1000K. The calculated results show that in the initial reaction pathways of TBO with OH radical, the reaction is dominated by OH addition to the double bonds, and H-abstraction pathways can be negligible at low to medium temperature. The total rate constant computed is 4.56 × 10−10 cm3 molecule−1 s−1 at 298 K, which is consistent with the experimental data. The Arrhenius equation of the total rate constants can be fitted as k t o t a l = 2.20 × 10 − 21 T 3.1 e x p (2499.2 / T) in the temperature range of 220–1000 K. In the presence of O2 and NO, the major degradation products of TBO with OH radical are acetone and 4-methyl-3,5-hexadienal, which are in reasonable agreement with the experimental observations. Furthermore, the ozone formation potential of TBO together with the effects of the TBO oxidation products have also been discussed in detail in the paper. [ABSTRACT FROM AUTHOR]

Thermally activated delayed fluorescence (TADF) molecules with dual emission have attracted extensive attention recently. However, the dual emission mechanism is complex and difficult to be studied especially in solid state. In this paper, asymmetrical diphenylketone derivatives CPzP and CPzPO are investigated in both benzene and in aggregation state with polarisable continuum model (PCM) and combined quantum mechanics and molecular mechanics (QM/MM) method respectively. It is found that there are both quasi-axial (ax) and quasi-equatorial (eq) conformations for CPzP and CPzPO in benzene. The ax conformation is responsible for the high energy band emission, while the low energy band emission is contributed by eq conformations. The dimers with intermolecular hydrogen bond have similar emission wavelengths with monomers. The small energy gap between the first singlet excited state and the first triplet excited state as well as large reverse intersystem crossing rate in eq conformations confirms the generation of TADF in eq conformation, which agree with experimental results that the low energy band emission is TADF. Our calculation results revealed the dual emission mechanism of two TADF molecules, which would favor the understanding of light emitting properties and the design of new type dual emission TADF emitters. [ABSTRACT FROM AUTHOR]

Predicting acute oral toxicity LD50 of chemicals in rats is a challenge since many factors affect toxicity data. In this paper, 40 descriptors were successfully used to develop a quantitative structure–activity relationship model for 8448 rat acute oral toxicity logLD50 by applying the random forest (RF) algorithm. To develop the optimal RF model, a training set (5914 chemicals) was used to establish models, a validation set (1267 chemicals) used to tune RF parameters and a test set (1267 chemicals) used to assess the performance of RF models. It yielded correlation coefficients R of 0.9695 and rms errors (log unit) of 0.3171 for the training set, R = 0.8322 and rms = 0.2889 for the validation set and R = 0.8335 and rms = 0.3060 for the test set. More than 99% of rat acute oral toxicity logLD50 in the dataset can be accurately predicted, although the dataset is large. [ABSTRACT FROM AUTHOR]

This paper computes the vibrational partition function of some diatomic molecules using an improved energy spectrum obtained recently with the q-deformed hyperbolic Scarf-like potential. Compared to the experimental energy curves, this potential proved to represent well the interaction between the atoms in the studied molecules. The related thermodynamic functions are derived for the K 2 , ScI and L i 2 molecules. Results demonstrated that the computed molecular entropy is in very good agreement with the experimental data for a large range of temperature values. In addition, results are given for the ScI molecule for which no experimental entropy values exist. Our results can serve as a reference to experimental studies in chemical physics. [ABSTRACT FROM AUTHOR]

Hydrogen storage has become a challenge for many researchers in recent years because it is a clean, cheap, and non-pollutant molecule existing in nature. Hence, in this paper, we report the hydrogen storage capability of P, Ni/P, Pt/P and Pd/P-embedded heptazine graphitic carbon nitride (hgCN) systems utilising the first-principle simulations. The structures of transition metal-modified hgCN were relaxed and found the stable position of the metal elements over the hgCN. The results of simulations revealed that the H2 molecules interacted feebly with the P-doped hgCN but were strongly adsorbed on the introduced active site of the metal atoms in the embedded hgCN with improved adsorption. The adsorption energy (Eads) of H2 molecules on the Pt/P-codoped hgCN (Eads = −2.749 eV) was much higher than many adsorbents such as graphene, graphane, graphyne, MoS2, B4N, boron carbide nanocage, etc. With adsorption of H2 molecules over the modified hgCN, the optimised structures, charge density and conductivity of systems significantly modulated. Based on these results, it is concluded that these modified hgCN (especially Pt/P-codoped) are promising candidates in the field of hydrogen storage in comparison to all other considered adsorbents. [ABSTRACT FROM AUTHOR]

In this paper, we determine the approximate eigenvalue bound state solution of the radial Schrodinger equation in three-dimension in the presence of the Aharonov-Bohm flux field with two-term diatomic molecular potential in point-like global monopole (PGM) defect. We analyse the effects of factors, such as topological defects, background curvature associated with topological defects as well as the potential. We also show that the energy levels shift due to the presence of the magnetic flux which gives us an analogue of the Aharonov-Bohm effect for the bound state. Finally, we apply the quantum system for some known potential models, such as q-deformed Hulthen-type potential and Manning-Rosen potential, and discussed the effects of various factors on the eigenvalue solutions. [ABSTRACT FROM AUTHOR]

Methyl isocyanate (CH3NCO) is an important agricultural and industrial precursor and emission from wildfires. In this paper, we study thermodynamic, kinetic and mechanistic approach of CH3NCO with OH radical and Cl atom using M06-2X level in combination with 6-311++G(d,p) basis set, and corrected by relatively accurate the single point CCSD(T) method. The rate constants of the title reactions are calculated in the temperature range of 200 and 400 K. The reactions exhibit a positive temperature depending on rate constants and fitted to the three-parameter Arrhenius expressions: kOH = 2.76 × 10−19 T2.65 exp[−486/T] and kCl = 3.51 × 10−18 T2.28 exp[95/T] with Wigner's and kOH = 4.95 × 10−19 T2.57 exp[−504/T] and kCl = 1.20 × 10−17 T2.11 exp[63/T] with Eckart's tunnelling corrections between 200 and 400 K. The calculated rate constants for the CH3NCO + OH/Cl reaction are in very good agreement with the previously reported experimental values. Thermochemical data (ΔH°298 K and ΔG°298 K) illustrate the feasibility and spontaneity of the title reactions. The atmospheric degradation mechanism of CH3NCO is discussed. The OH/Cl-driven tropospheric lifetimes and global warming potential (GWP) for CH3NCO were calculated. It was concluded that CH3NCO existed in the Earth's atmosphere for a few days and its GWP is not significantly large. The ozone formation potential of CH3NCO was also reported in this work. [ABSTRACT FROM AUTHOR]

The Rayleigh – Schrödinger perturbation series possesses the property that can be termed multiple convergence. This property is that using appropriate multivalued approximants it enables the energy levels of several states to be calculated from the coefficient of a series constructed for one state. This multiple convergence property has been previously demonstrated in a number of papers: for linear anharmonic oscillators (Sergeev and Goodson J. Phys. A: Math. Gen. 31 4301 (1998)), for one-dimensional periodic problem (Fernandez and Diaz 2001, Eur. Phys. J. D15 41), for electronic sates of diatomic molecules (Jordan Int. J. Quant. Chem. Symp. 9, 325 (1975); Goodson Mol. Phys. 110, 1681 (2012)) and for vibrational states of formaldehyde (Duchko and Bykov Phys. Scr. 94, 105403, (2019)). In this paper, we examine multiple convergence as applied to the vibrational states of the hydrogen sulphide which exhibits the strong local mode behaviour. We show that property of multiple convergence is connected with the polyad structure of the vibrational energy spectrum and the strength of anharmonic resonance coupling between the states. [ABSTRACT FROM AUTHOR]

Circumscribing benzenoid polycyclic aromatic hydrocarbons was first introduced in 1982 under the topic of a periodic table for benzenoid hydrocarbons and isomer enumeration. This circumscribing process was rendered on benzene to successively generate coronene, circumcoronene, dicircumcornene, and so on as the first constant-isomer series. Subsequently, numerous benzenoid constant-isomer series were uncovered because of the coupling of the benzenoid periodic table (Table PAH6) and circumscribing. Circumscribing even carbon monocyclic polyenes produced [n]cyclacenes (n = number of hexagonal rings) which are monotier nanotubes. Starting with [n]cyclacenes and successive circumscribing generates (n,0) Zigzag nanotubes of increasing length. Successive circumscribing cycloparaphenylenes leads to (n,n) Armchair nanotubes of increasing length. Successive supercircumscribing cycloparaphenylenes leads to total-resonant-sextet Armchair nanotubes of maximum stability. Circumscribing polycyclic conjugated systems was subsequently introduced for other ring sizes. Circumscribing polycyclic hydrocarbons with a combination of pentagonal and hexagonal rings leads to fullerenes when 12 pentagonal ring is reached. Generation of altans is a specialised type of circumscribing in which the encircling annulene is attached via its alternate degree-2 vertices to the degree-2 vertices of the core structure. We show that monocapped nanotubes are circumscribed altans. [ABSTRACT FROM AUTHOR]

The structural, electronic and Li-ion diffusion properties of LiFePO4 (010) surface modified by graphene have been investigated by first-principles calculation under the DFT+U framework. The calculated formation energy indicates that the LiFePO4 (010) surface modified with graphene is energetically favourable. It is found that strong C-Fe and C-O covalent bonds are formed at the modified interface, and the band gap of LiFePO4 modified with graphene is narrowed, indicating better electronic conductive properties. The energy barrier for the diffusion of Li-ion along the bchannel perpendicular to the (010) surface is calculated using the method of finding the transition state. The results show that the energy barrier of the modified system is reduced, indicating that the surface modification of LiFePO4 by graphene can improve the surface diffusion rate of Li-ions. [ABSTRACT FROM AUTHOR]

Photochemical reactions often involve states that are closely coupled due to near degeneracies, for example by proximity to conical intersections. Therefore, a multistate method is used to accurately describe these states; for example, ordinary perturbation theory is replaced by quasidegenerate perturbation theory. Multiconfiguration pair-density functional theory (MC-PDFT) provides an efficient way to approximate the full dynamical correlation energy of strongly correlated systems, and we recently proposed compressed multistate pair-density functional theory (CMS-PDFT) to treat closely coupled states. In the present paper, we report the implementation of analytic gradients for CMS-PDFT in both OpenMolcas and PySCF, and we illustrate the use of these gradients by applying the method to the excited states of formaldehyde and phenol. [ABSTRACT FROM AUTHOR]

By a historical overview, we show the importance of a laconic paper by Kolos and Wolniewicz dating to 1962 [Phys. Lett. 5(2), 222–223 (1962)], in which they applied the variational method for the hydrogen molecule. In the first part of this perspective (say till 1996), the experiments on electron molecule scattering (including hydrogen) developed a vast range of techniques, even if the results were far from being congruent [Riv. Nuovo Cimento 19/3, 1996]. In turn, in the last years, we have observed the quickly rising applicability of theoretical methods, like convergent-close coupling [Zammit et al. Phys. Rev. Lett. 116, 233201 (2016)] and R-matrix [Meltzer & Tennyson, J. Phys. Phys. B 53, 245203 (2020)]. The mutual agreement between theories and experiments allows defining recommended cross-sections for electron and positron scattering from zero to sub-relativistic energies. This, in turn, enables to check the dispersion relation, i.e. the interdependence between the zero-energy integral elastic, the high-energy elastic differential at zero angle, and the integral of the total cross-section from zero to infinity. Such a relation holds, within the experimental uncertainties, for positrons. For electrons, a big discrepancy points to the importance of the exchange effects in the e − − H 2 scattering. [ABSTRACT FROM AUTHOR]

The single-reference coupled-cluster (CC) method is one of the most efficient approaches for describing electron correlation effects in atoms and molecules but its successful application is limited to states dominated by a single Slater determinant. In cases where several determinants dominate the wave function expansion, the multi-reference (MR) CC formulations are required. They usually use the effective Hamiltonian formalism which allows dealing with two types of electron correlation appearing in the MR cases: nondynamic and dynamic. There are two MR-CC formulations of this type: the Hilbert space CC method and the Fock-space (FS) one. In the paper, a version of the FS-CC method designated for the description of systems with three-valence electrons is being considered. The idea of the intermediate Hamiltonian (IH) reformulation of the standard FS-CC method, which simplifies the calculations and avoids the intruder state problem, is discussed in this context. A new IH-FS-CC approach is presented which takes advantage of the redefinition of the normal ordering of the FS cluster expansion introduced by Lindgren. The redefinition significantly simplifies the IH-FS-CC formalism and lowers the computational cost of the calculations. The advantages of the new IH formulation are discussed in detail for the case of the FS-CC method in which the lowest-order cluster operators are included in all sectors of the Fock-space, including the three-valence one. [ABSTRACT FROM AUTHOR]

Quasi-bound resonances of H 2 are produced via two-photon photolysis of H 2 S molecules as reactive intermediates or transition states and detected before decay of the parent molecule into three separate atoms. As was previously reported [K. F. Lai et al., Phys. Rev. Lett. 127, 183001 (2021)] four centrifugally bound quantum resonances with lifetimes of multiple μs, lying energetically above the dissociation limit of the electronic ground state X 1 Σ g + of H 2 , were observed as X (v , J) = (7 , 21) ∗ , (8 , 19) ∗ , (9 , 17) ∗ , and (10 , 15) ∗ , while also the short-lived ( ∼ 1.5 ns) quasi-bound resonance X (11 , 13) ∗ was probed. The present paper gives a detailed account on the identification of the quasi-bound or shape resonances, based on laser detection via F 1 Σ g + - X 1 Σ g + two-photon transitions, and their strongly enhanced Franck-Condon factors due to the shifting of the wave function density to large internuclear separation. In addition, the assignment of the rotational quantum number is verified by subsequent multi-step laser excitation into autoionisation continuum resonances. Existing frameworks of full-fledged ab initio computations for the bound region in H 2 , including Born-Oppenheimer, adiabatic, non-adiabatic, relativistic and quantum-electrodynamic contributions, are extended into the energetic range above the dissociation energy. These comprehensive calculations are compared to the accurate measurements of energies of quasi-bound resonances, finding excellent agreement. They show that the quasi-bound states are in particular sensitive to non-adiabatic contributions to the potential energy. From the potential energy curve and the correction terms, now tested at high accuracy over a wide range of energies and internuclear separations, the s-wave scattering length for singlet H+H scattering is determined at a = 0.2735 31 39 a 0 . It is for the first time that such an accurate value for a scattering length is determined based on fully ab initio methods including effects of adiabatic, non-adiabatic, relativistic and QED with contributions up to m α 6 . [ABSTRACT FROM AUTHOR]

In this paper, we have conducted a systematic research on the single- and double-sided adsorption models of Al atoms on the surface of graphene. The results show that the adsorption energy of single-sided Al atoms on each active site on perfect graphene is about − 1.0 eV . When a single C vacancy exists, the adsorption energy of Al atom on the surface of single-vacancy graphene is − 5.42 eV , and when two C vacancies exist, the adsorption energy of Al atom on the surface of double-vacancy graphene is − 2.76 eV . Subsequently, the adsorption behaviour of Al atoms on both sides of graphene was systematically studied. The calculation results showed that the adsorption energy of Al atoms on both sides of perfect graphene was twice that of Al atoms on one side of perfect graphene. At the same time, when Al atoms are adsorbed on both sides of graphene with vacancies, the adsorption performance is improved from − 2.25 eV to − 4.84 eV . In conclusion, the existence of vacancies is of great significance for the adsorption performance of Al atoms on the graphene surface. Our research results provide a theoretical basis for the further development of graphene-metal matrix composites. [ABSTRACT FROM AUTHOR]

In this paper, various substituted 3t-pentyl-2r,6c-diarylpiperidin-4-one oxime picrates were synthesised and characterised by elemental analysis, FT-IR, NMR, UV–Visible and Fluorescence spectral techniques. For compound 1, NMR spectral assignments were made unambiguously by their one-dimensional (1H and 13C NMR) and two-dimensional (1H–1H COSY, NOESY, HSQC and HMBC) spectra. The observed chemical shifts and coupling constants suggest that compounds 1–7 adopt normal chair conformation with the equatorial orientation of all the substituents like aryl group at C(2) and C(6) and pentyl group at C(3). Compounds 2 and 7 exhibited potent anti-bacterial activity and fungal activity against all the tested strains while all the other compounds showed moderate activity. The molecular structure of compounds (1–7) was optimised at the density functional theory (DFT)/B3LYP/6-311++G(d,p) level of basis set. The calculated first hyperpolarisability (β0) values show that all the molecules might have non-linear optical (NLO) behaviour. The HOMO–LUMO transition implies that intra-molecular charge transfer takes place within the molecule. The molecular electrostatic potential (MEP) surface is used to understand the reactive sites of a molecule. [ABSTRACT FROM AUTHOR]

We have addressed the problem of controlling a regime change in a quasi-2D system of magnetic disk-like particles by means of the strength and direction of an applied magnetic field. In the present study, two typical directions have been addressed, i.e. a y-direction field parallel to the 2D plane and a z-direction field normal to that plane of the particle disk. It is shown that the direction of an applied magnetic field is a significant factor in particle aggregation and can give rise to different regime changes. That is, an applied magnetic field parallel to the 2D system plane functions to induce a regime change in the aggregate structure from linear column-like particle clusters into a knitting-pattern formation, whereas in the case of an applied field normal to the 2D plane, a regime of long column-like clusters transforms into a particle distribution with no discernible internal structure. Key points of the present paper: The direction of an applied magnetic field may give rise to significantly different regime changes in particle aggregation. An applied magnetic field parallel to the 2D system plane induces a regime change from long linear column-like clusters into a knitting-pattern formation. A magnetic field in a direction normal to the 2D plane induces a regime change from long linear column-like clusters into a regime with no discernible internal structure. The strength and the direction of an applied magnetic field is a feasible tool for controlling a regime change in the aggregate structure. [ABSTRACT FROM AUTHOR]

The paper describes methods and fast computational algorithm for building effective Hamiltonians in molecular physics using perturbative approach. Separations of fast and slow variables are considered in the framework of contact transformations (CT). The particular focus is on a systematic derivation of effective models for rovibrational spectroscopy from ab initio-based potential energy surfaces with an exhaustive review of previous studies in this field. We consider applications to several types of polyads coupled by Fermi, Coriolis, Darling-Dennison and other types of resonance interactions with examples for asymmetric top, symmetric top and spherical top molecules. A flexible choice of the modelling operator accounts for strong couplings of various types of nuclear motion in molecules among closely lying levels including vibrational resonance schemes (2:1:2...), (2:1:2:1), (4:2:6:3), (3:2:1:2:1:1), etc. that occur for C2v, C3v and Td molecules and their isotopic species. The method is implemented in the MOL_CT programme suite, which offers a complementary tool to variational methods in terms of convergence and computational time. The range of applications is also different. The goal of the CT method is providing mathematical models for analyses of molecular spectra with the high-resolution accuracy using physically meaningful parameters derived from ab initio functions. [ABSTRACT FROM AUTHOR]

This paper is the first of two back-to-back works, whose goal is to update the existing line positions and intensities spectroscopic parameters for the 5.8 µm region of nitric acid in the HITRAN or GEISA spectroscopic databases. This first study is devoted to the generation of first linelists for the ν2+ν9-ν9, ν2+ν7-ν7 and ν2+ν6-ν6 hot bands in the 5.8 µm region, whereas the second study will concern the positions and intensities for the ν2 band centred at 1709.567 cm−1. High-resolution Fourier transform spectra were recorded in the 5.8 µm and in the 4.2–4.6 µm spectral ranges. The identification of the ν2+ν9, ν2+ν7 and ν2+ν6 bands of HNO3 at 2165.0036, 2285.9657 and 2351.216 cm−1, respectively, was performed, and several assignments were confirmed by searching for ν2+ν9-ν9 and ν2+ν7-ν7 transitions within those of ν2 at 5.8 µm. Both ν2+ν6 and ν2+ν9 bands are highly perturbed. Surprisingly, both ν2+ν9 and ν2+ν9-ν9 bands exhibit large amplitude torsional splittings of ∼0.043 cm−1. This is presumed to be due to the existence of an anharmonic resonance that couples together the 2191 energy levels with those of a dark state involving high excitation in the ν9 large amplitude OH torsional mode. [ABSTRACT FROM AUTHOR]