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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]

A scientific biography is presented as an introduction to a collection of papers by his colleagues and co-workers honouring the scientific contributions and legacy of the late Dr. Timothy J. Lee (1959–2022). Tim Lee performed highly regarded research on the methods and applications of computational quantum chemistry, particularly coupled cluster theory, and computational spectroscopy, with impacts in interstellar chemistry, aiding NASA missions, atmospheric chemistry, as well as fundamental science. His presence is deeply missed. [ABSTRACT FROM AUTHOR]

This paper conducts a computational investigation of the phase behaviour of $ \textrm{C}{\textrm{H}_4} $ C H 4 - $ \textrm{C}{\textrm{O}_2} $ C O 2 binary system, utilising the SAFT-VR Mie equation of state alongside molecular dynamics (MD) simulations. Molecular parameters for pure $ \textrm{C}{\textrm{H}_4} $ C H 4 and $ \textrm{C}{\textrm{O}_2} $ C O 2 compounds were obtained by fitting the SAFT-VR Mie EOS to vapour pressure and saturated liquid density experimental data. The research first validates the SAFT-VR Mie EOS on thermodynamic properties and vapour–liquid equilibria for different compositions, pressures, and temperatures of pure $ \textrm{C}{\textrm{H}_4} $ C H 4 , $ \textrm{C}{\textrm{O}_2} $ C O 2 , and $ \textrm{C}{\textrm{H}_4} $ C H 4 - $ \textrm{C}{\textrm{O}_2} $ C O 2 mixtures with the newly extracted parameters. The study confirms the EOS's accurate prediction of coexistence properties, including pressure, density, and phase-equilibrium curve. MD simulations were performed using the LAMMPS software package, with Mie force field parameters derived from this study for non-bonded interactions. Simulations were conducted using three other force fields (OPLS-UA, UFF, and GAFF) to compare their performance with our approach. The simulation results were compared to laboratory data, or REFPROP, in the absence of laboratory data. The results showed a relatively good agreement, indicating that combining SAFT-VR Mie EOS and MD simulations is a reliable predictive tool for designing gas processing and gas storage applications involving $ \textrm{C}{\textrm{H}_4} $ C H 4 - $ \textrm{C}{\textrm{O}_2} $ C O 2 mixtures. This approach also mitigates the need for expensive and hazardous high-pressure laboratory techniques. [ABSTRACT FROM AUTHOR]

Recently, the new fluorescent probe 5'-amino-2-(2'-hydroxyphenyl) benzimidazole (P1) utilised in the ultrasensitive detection of phosgene based on excited-state intramolecular proton transfer (ESIPT) was synthesised experimentally (Z. J. Li et al., RSC Adv., 2021, 11, 10836). In this paper, the ESIPT process of the P1 molecule was theoretically investigated in detail by density functional theory and time-dependent density functional theory methods. The molecular structures in the ground state (S0) and the first excited state (S1) were optimised, and the infrared vibrational spectra, the frontier molecular orbitals, the potential energy curves were discussed. The calculated electronic spectra data is consistent with experimental observation. Also studied in detail is the mechanism of the ESIPT reaction, which confirms that the hydrogen bond can be enhanced in the S1 state. It will provide significant theoretical reference for future fluorescent probe experiments. Additionally, the react site is verified by calculating the electrostatic potential. ΔG < 0 indicates that the reaction of P1 with COCl2 is exothermic and occurring spontaneously. These results fully confirm that P1 is a good sensor for detecting phosgene. [ABSTRACT FROM AUTHOR]

An exhaustive review of the measured rovibrational transitions of the $ ^{16} $ 16 O $ ^{12} $ 12 C $ ^{32} $ 32 S isotopologue of carbonyl sulphide is undertaken. A comprehensive analysis of data from 100 papers is carried out using a consistent set of harmonic oscillator quantum numbers which are recommended for future studies. A corrected compilation of 14,071 OCS transitions is then subjected to a Measured Active Rotational-Vibrational Energy Levels (MARVEL) analysis, resulting in 5729 empirical energy levels. The uncertainties corresponding to these levels are analysed using different procedures; the newly implemented bootstrap method is used to provide final uncertainties. [ABSTRACT FROM AUTHOR]

Large-amplitude vibrational motion influences the rovibrational structure of molecules that tunnel between multiple wells. Reaction path (RP) Hamiltonians, and curvilinear coordinates more generally, are useful for modelling pure vibrational motion in these systems and provide a practical framework for calculating accurate ab initio anharmonic vibrational energies and tunnelling splittings with perturbation theory. These computational tools also offer the means to address rotation-vibration coupling associated with large-amplitude motion in rotating molecules. In this paper, we incorporate the reduced axis system (RAS) frame embedding with RP Hamiltonians and second-order vibrational Møller-Plesset perturbation theory (VMP2). Because the RP-RAS Hamiltonian eliminates rotation-vibration momentum coupling everywhere along a one-dimensional reaction path, it is well suited for rovibrational VMP2 methods, the convergence of which relies critically on approximate vibration-vibration and vibration-rotation separability. The accuracy of this combined RP-RAS-VMP2 scheme is demonstrated by comparisons with numerically exact variational calculations and VMP2 parameters based on traditional Eckart embeddings for reduced-dimension models of torsional tunnelling in hydrogen peroxide and inversion tunnelling in cyclopropyl radical. The favourable computational scaling of VMP2 makes it a promising strategy for calculating accurate tunnelling-rotation parameters for medium-sized and larger molecules in full dimensionality. [ABSTRACT FROM AUTHOR]

The carbon trimer, $ \hbox {C}_3 $ C 3 also known as propadienediylidene, is a quasi-linear molecule with an unusual electronic structure and a very flat bending potential in its ground electronic state. $ \hbox {C}_3 $ C 3 is an important species in astrophysics and carbon plasmas. Observed transition wavenumbers within and between the $ \tilde {X}\,^1\Sigma ^+_{\rm g} $ X ~ 1 Σ g + and $ \tilde {A}\,^1\Pi _{\rm u} $ A ~ 1 Π u states of $ \hbox {C}_3 $ C 3 are extracted from 21 papers and then subjected to a Measured Active Rotational-Vibrational Energy Levels (MARVEL) analysis: a corrected list of 4940 transitions are inverted to yield 1887 empirical energy levels. Uncertainties for these levels are determined using a newly implemented bootstrap method. These levels will provide input for developing a full spectroscopic model for $ \hbox {C}_3 $ C 3 which can used to generate a line list for the $ \tilde {X}\,^1\Sigma ^+_{\rm g} $ X ~ 1 Σ g + and $ \tilde {A}\,^1\Pi _{\rm u} $ A ~ 1 Π u states. [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]

In this paper, the adsorption behaviours of the MeOH-DMC azeotropic system onto α-Al2O3 were investigated from both practical and theoretical aspects for the first time. The experimental results showed that the static MeOH- and DMC-adsorption capacities of α-Al2O3 were 325.52 and 70.32 mg·g−1, respectively. The selectivity S was 4.63 and the dynamic separation factor α was 4.2. Then, density functional theory (DFT) was used to reveal possible interactions between the constructed azeotrope clusters and the α-Al2O3 (0 0 1) surface. Molecular simulation results indicated that although there were different azeotropic clusters in the bulk liquid, most of the H-bonds were destroyed when they approached the solid surface. The MeOH dimers were adsorbed onto both Al and O sites via chemisorption and H-bonds, while DMC monomers mainly occupied the Al sites. Thus, chemisorption on Al sites and multi-layer adsorption played a critical role in selective adsorption. Moreover, the competition between MeOH and DMC for adsorption sites might also cause a big difference between the MeOH- and DMC-adsorption capacities of α-Al2O3. [ABSTRACT FROM AUTHOR]

The redox balance between HClO and H2S is essential for the physiological and pathological properties of organisms. Therefore, monitoring the redox process between HClO and H2S is of great significance. Shen et al. synthesised a reversible ratiometric fluorescence probe BT-Se based on excited state intramolecular proton transfer (ESIPT) reaction for the detection of HClO and H2S in previous experiments. When BT-Se detects HClO, it will be oxidised to a new substance which is named BT-SeO, and BT-SeO can be reduced to BT-Se by detecting H2S. BT-Se and BT-SeO emit different colours of fluorescence to realise detection. In this paper, the attribution of the fluorescence peak and the luminescence mechanism are studied. The bond parameters, infrared (IR) vibrational frequency, interaction region indicator (IRI) and the potential energy curve are analysed to demonstrate that the excited state is easier to conduct the ESIPT process. The combination of frontier molecular orbitals (FMOs) and hole–electron analysis reveals the charge excitation characteristics. This work suggests that the yellow and blue fluorescence observed in the experiment is emitted by the keto structures of BT-Se and BT-SeO, respectively. Our research will provide an important theoretical basis for the detection of photophysical phenomena in reversible ratiometric fluorescent probes. [ABSTRACT FROM AUTHOR]

Based on the first principle, this paper uses the generalised gradient approximation density functional theory and slab model to investigate the dissociation of methane (CH4→CH3 + H) on the surfaces of Co group (Co, Rh, Ir) and Ni group (Ni, Pd, Pt), and investigate the influence of PtIr(100), PdRh(100) and PtPd(100) on methane decomposition. From the calculated activation energies of methane dissociation on single metal surfaces and alloy surfaces,we find that Pt and Ir are better catalysts for methane dissociation in the single metals studied. In addition, methane dissociation (CH4→CH3 + H) on PtIr(100) and PdRh(100) surfaces are easier than that on single metal surfaces(Co, Rh, Ir, Ni, Pd, Pt). [ABSTRACT FROM AUTHOR]

Oil-immersed power transformers generate characteristic gases after failure,Therefore, it is necessary to analyse and monitor the soluble gases in transformer oil samples. In this study, the DFT calculation method was used to study the adsorption properties of H2, CO, C2H2, and C2H4 gases in oil on both intrinsic MoTe2 and Rh-doped MoTe2 films. In order to analyse the adsorption characteristics, this paper first obtains the most stable Rh-doped MoTe2 monolayer model through the modelling and computational analysis of different doping sites, then, the adsorption of these gases on the material surface is studied by analysing adsorption energy, charge transfer, total state density, parting density, energy band structure, differential charge density map, molecular front orbital and desorption time, and finally concludes that Rh-MoTe2 monolayer film is the ideal material for hydrogen sensing elements, due to the extremely long desorption time of CO gas, indicating that CO gas is hard to desorption on the surface of adsorbent,which shows that this process has played a certain role in promoting CO removal. Highlights Study focused on gas adsorption using DFT: Rh-MoTe2 ideal for hydrogen sensing and effective for CO removal, intrinsic MoTe2 ineffective and required metal doping. Rh doping enhanced conductivity and gas adsorption capacity in MoTe2. Rh-MoTe2 was suitable for detecting H2, C2H2, and C2H4 gases. Desorption times vary with temperature, with CO removal particularly effective at higher temperatures. Findings suggest potential applications for Rh-MoTe2 in gas sensing and removal. [ABSTRACT FROM AUTHOR]

This paper presents a study on the optimisation of laser pulse parameters using an optimal control theory based adaptive simulated annealing technique. The objective of this study is to obtain a cost-effective laser pulse that can selectively excite the vibrational state and cause photo-dissociation of the C–H bond in a methane molecule. We have optimised both sinusoidal and linear ramped pulses using the proposed technique, and incorporated a linear chirping in the field as well. The results demonstrate the effectiveness of the proposed approach in designing laser pulses for targeted molecular excitation and dissociation. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic has significantly affected both the global economy and human health. COVID-19 is a single-stranded RNA virus that spreads through the inhalation of viral droplets. Its genome encodes four structural proteins: the envelop protein, spike protein, membrane protein, and nucleocapsid protein. The virus's capsid is a protein shell that contains a positive RNA strand that allows it to take control of human cell machinery. Currently, the only treatments for COVID-19 are preventative measures and immunization. Some of the anti-COVID and anti-cancer medications used to combat this virus include Camptothecin Polymer, Hyaluronic Acid-curcumin, and Hydroxychloroquine. Graphs are used extensively in chemical investigation to provide a mathematical model of molecules. The selection of graph invariants, formerly known as molecular structure descriptor's, is the mathematical modelling of chemical compounds' physio-chemical, pharmacologic, and toxicological aspects. This paper presents a new technique to compute topological indices for three types of chemical networks for a few anti-COVID and anti-cancer medications. Our findings suggest that these indices show a strong association with the acentric factor and entropy, which make them effective in QSPR and QSAR analysis with high accuracy. [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.

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]

The emergence of oxygenic photosynthesis was a major event in Earth's evolutionary history and was facilitated by chlorophylls (a major category of photopigments). The accurate modelling of photopigments is important to understand the characteristics of putative extraterrestrial life and its spectral signatures (detectable by future telescopes). In this paper, we perform a detailed assessment of various time-dependent density-functional theory (TD-DFT) methods for predicting the absorption spectra of chlorophyll a, with particular emphasis on modern low-cost approximations. We also investigate a potential extraterrestrial photopigment called phot0 and demonstrate that the electronegativity of the metal ion may exert a direct influence on the locations of the absorption peaks, with higher electronegativity inducing blue-shifting and vice-versa. Based on these calculations, we established that global-hybrid approximations with a moderate percentage of exact exchange – such as M06 and PW6B95 – are the most appropriate compromise between cost and accuracy for the computational characterisation of photopigments of astrobiological interest. We conclude with a brief assessment of the implications and avenues for future research. [ABSTRACT FROM AUTHOR]

Cholesky decomposition (CD) of the two-electron integrals and the resolution-of-identity (RI) techniques are established inner projection methods to efficiently evaluate two-electron integrals. Both approaches share the notion of an auxiliary basis set as a mean to reduce the scaling. In the past years, the close relationship between the two approaches has fostered developments on how to systematically derive unbiased auxiliary basis sets – atomic CD (aCD) and atomic compact CD (acCD) auxiliary basis sets, different to the precomputed auxiliary basis sets. The accuracy of these approximations in the RI approach can be further improved via an explicit correction of the one-centred two-electron integrals, which is the main object of this research. Correcting the one-centred two-electron integrals directly, which scales linear with system size, is expected to provide a new degree of freedom to the design of auxiliary basis sets. This can either be used to gain faster convergence towards the conventional treatment of the two-electron integrals or as a mean to design lighter auxiliary basis sets while maintaining the same accuracy as of the uncorrected approach. The benchmarks of the one-centre corrections applied to several auxiliary basis set types were investigated in this paper. [ABSTRACT FROM AUTHOR]

The recent identification of interstellar molecules HCCCHCCC and HCCCCS in TMC-1 has prompted an ab initio investigation of these isomers. The isomers of HCCCHCCC have been studied previously but not so much HCCCCS. In this paper we carry out high-level CCSD(T) calculations to characterise the lowest eleven isomers of HCCCCS. We also apply complete basis set extrapolation including core correlation and relativistic effects to further investigate the key isomers and provide high-precision rotational constants which will hopefully aid astronomers in their assignments. Source: This image has been adapted from licensed under CC BY-SA 3.0. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

The carbon trimer, $ \hbox {C}_3 $ C 3 also known as propadienediylidene, is a quasi-linear molecule with an unusual electronic structure and a very flat bending potential in its ground electronic state. $ \hbox {C}_3 $ C 3 is an important species in astrophysics and carbon plasmas. Observed transition wavenumbers within and between the $ \tilde {X}\,^1\Sigma ^+_{\rm g} $ X ~ 1 Σ g + and $ \tilde {A}\,^1\Pi _{\rm u} $ A ~ 1 Π u states of $ \hbox {C}_3 $ C 3 are extracted from 21 papers and then subjected to a Measured Active Rotational-Vibrational Energy Levels (MARVEL) analysis: a corrected list of 4940 transitions are inverted to yield 1887 empirical energy levels. Uncertainties for these levels are determined using a newly implemented bootstrap method. These levels will provide input for developing a full spectroscopic model for $ \hbox {C}_3 $ C 3 which can used to generate a line list for the $ \tilde {X}\,^1\Sigma ^+_{\rm g} $ X ~ 1 Σ g + and $ \tilde {A}\,^1\Pi _{\rm u} $ A ~ 1 Π u states. [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]

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]

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]

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]

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]

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]

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 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 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 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 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]

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]