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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]

A scientific biography serves as an introduction to a collection of papers honoring the significant contributions to the field of Statistical Mechanics by the late Luis Felipe Rull (1949-2022) and José Luis Fernandez Abascal (1952). Both dedicated their careers to the understanding of condensed matter systems, not only making substantial scientific contributions but also pioneering and expanding computer simulation methods in Spain. They were instrumental figures in the Spanish Statistical Mechanics School, which has flourished due to the efforts of a generation, including Luis and José Luis, who transformed Spanish science since 1975 and laid the foundation for our current achievements. [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]

The fields of statistical physics and single-cell genomics have traditionally evolved independently, each contributing unique insights to their respective domains. However, recent advances have unveiled intriguing parallels between these seemingly disparate disciplines. This paper delves into the remarkable similarities underlying the fundamental principles governing both systems, shedding light on their shared mathematical frameworks, information processing dynamics and emergent behaviours. We explore how energy landscapes in statistical physics correspond to gene expression landscapes, and how the study of disordered phenomena may shed light on the cellular heterogeneity observed in gene expression profiles. Some parallels between phase transitions and critical transitions in cellular differentiation processes are discussed. Emergent behaviours and collective phenomena, central to both fields, offer opportunities for cross-disciplinary insights. By examining these similarities, we can potentially transfer analytical tools and methodologies between these domains. In summary, this paper underscores some unexpected yet profound parallels between statistical physics and single-cell genomics. By embracing the shared mathematical and conceptual frameworks, researchers can unlock new avenues for discovery, enriching our understanding of complex systems ranging from the microscopic world of molecules to the intricate processes governing cellular behaviour. [ABSTRACT FROM AUTHOR]

We considered a dispersion composed of polydisperse cubic hematite particles in thermodynamic equilibrium, and conducted cluster-moving Monte Carlo (MC) simulations to investigate the internal structure of cubic particle aggregates in a quasi-2D system. The investigation focused on various factors, such as the strength of magnetic particle–particle interaction, the standard deviation of the particle size distribution, and the volumetric fraction of particles. In a polydisperse system with a small standard deviation, cubic particles tended to aggregate and form closely packed structures with almost perfect face-to-face configuration, as in the case of a monodisperse system. In a polydisperse system with a larger standard deviation, only large particles tended to aggregate and form closely packed clusters with an aligned face-to-face configuration, while small particles moved as single particles in the system, because the magnitude of the magnetic moments is proportional to the particle volume. The magnetic interactions between small particles are not sufficiently strong for the particles to come into contact. Therefore, an increase in the standard deviation leads to unstable face-to-face contact within closely packed clusters. In a polydisperse system with a larger standard deviation, an increase in the volumetric fraction promotes aggregation, but smaller particles preserve their individual status. Highlights of the present paper: We developed a Monte Carlo simulation technique for suspension composed of polydisperse cubic hematite particles. We investigated dependence of aggregate structures of cubic particles on particle size distribution. In a polydisperse system with larger standard deviation, only large particles tend to aggregate to form closely packed clusters, while small particles remain as single particles. Increase in standard deviation leads to unstable face-to-face contact within closely packed clusters. [ABSTRACT FROM AUTHOR]

In this paper, we report a molecular dynamics study of the effect of the application of magnetic fields on the morphology of nematic nanobridges of 32,000 oblate Gay-Berne particles in slit pores favouring homeotropic anchoring. In absence of magnetic fields, previous studies show that there are different conformations of the nanobridge, depending on the slit pore width D and the wettability of the walls. Under the application of uniform magnetic field cycles, in which the intensity of the field is increased stepwise until a maximum value and then decreased at the same rate, switching between different nanobridge conformations can be observed if the magnetic field is applied in a perpendicular direction to the global nematic director of the nanobridge. However, there are situations in which the initial bridge conformation is recovered after the magnetic field application, indicating that the switching can only be observed if there are different locally stable nanobridge conformations under the same thermodynamic conditions. Moreover, magnetic fields can destabilise the nanobridge, leading to its breakdown into isolated nanodroplets attached to a single wall. [ABSTRACT FROM AUTHOR]

Discotic colloids give rise to a paradigmatic family of liquid crystals with sound applications in Materials Science. In this paper, Monte Carlo simulations are employed to characterise the low-temperature liquid crystal phase diagram and the vapour-liquid coexistence of discotic colloids interacting via a Kihara potential. Discoidal particles with thickness-diameter aspect ratios $ L^*\equiv L/D=0.5 $ L ∗ ≡ L / D = 0.5 , 0.3, 0.2 and 0.1 are considered. For the less anisotropic particles ( $ L^* \ge 0.2 $ L ∗ ≥ 0.2), coexistence of a vapour phase with the isotropic fluid and with the columnar liquid crystal phase is observed. As the particle anisotropy increases, the vapour-liquid coexistence shifts to lower temperatures and its density range diminishes, eventually merging with coexistences involving the liquid crystal phases. The $ L^*=0.1 $ L ∗ = 0.1 fluid displays a rich sequence of mesophases, including a nematic phase and a novel lamellar phase in which particles arrange in layers perpendicular to the nematic director. [ABSTRACT FROM AUTHOR]

Thermo-osmotic flows, generated by applying a thermal gradient along a liquid-solid interface, could be harnessed to convert waste heat into electricity. While this phenomenon has been known for almost a century, there is a crucial need to gain a better understanding of the molecular origins of thermo-osmosis. In this paper, we start by detailing the multiple contributions to thermo-osmosis. We then showcase three approaches to computing the thermo-osmotic coefficient using molecular dynamics; a first method based on the computation of the interfacial enthalpy excess and Derjaguin's theoretical framework, a second approach based on the computation of the interfacial entropy excess using the so-called dry-surface method, and a novel non-equilibrium method to compute the thermo-osmotic coefficient in a periodic channel. We show that the three methods align with each other, in particular for smooth surfaces. In addition, for a polarised graphene-water interface, we observe large variations of thermo-osmotic responses, and multiple changes in flow direction with increasing surface charge. Overall, this study showcases the versatility of osmotic flows and calls for experimental investigation of thermo-osmotic behaviour in the vicinity of charged surfaces. [ABSTRACT FROM AUTHOR]

In a recent paper, the effect of concentration fluctuations in a simple fully symmetric model of dilute electrolyte, confined between two planar electrodes, was investigated using constant charge simulations in the vicinity of the solute-solvent demixing transition. In agreement with previous theoretical findings it was shown that the total capacitance was enhanced by the occurrence of concentration fluctuations. In this work we will resort to constant potential simulations to show that the same effect is to be found in the differential capacitance. Additionally, here we will consider the effects of ion solvation by a polar solvent modelled by TIP4P/2005 water. Finally, the original fully symmetric ionic solute will be replaced by a three-site coarse grained model for a well know room temperature ionic liquid, 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMI] $ ^+ $ + [BF $ _4 $ 4 ] $ ^- $ − )). Our results show the presence of strong local fields within the capacitor due to incomplete local screening, and a marked asymmetry in the charge distribution. The expected capacity enhancement due to concentration fluctuations is completely mitigated by solvation effects and the response of the polar solvent to the external field. [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]

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]

A frontal polymerisation (FP) is obtained when a polymerisation creates a spatial front of the reaction. Because of the heat of the reaction associated, a temperature spatial front is also observed. In this paper, the usual chain polymerisation of acrylic acid (AA) is studied when the monomer forms a deep eutectic solvent (DES), i.e. a liquid similar to an ionic liquid. In this DES, AA behaves as a hydrogen donor and ethylammonium chloride as a hydrogen acceptor. The use of a DES is convenient as an effective polymerisation media because the heat of the reaction can be controlled. We study the rate and the heat of polymerisation during the formation of a front using micellar structures where a bifunctional peroxide hydrophobic initiator, abbreviated Luperox, dissolves successfully. Our experiments follow the FP using infrared images and rheology. We found that micellar aggregates of different sizes are interesting modulators of the polymerisation rate and heat of the reaction. Our results show that smaller aggregates produce higher rates of reaction with a decoupled increment of temperature; in contrast to what is observed with bigger aggregates: a slow reaction rate with a coupled moderate heat of reaction. [ABSTRACT FROM AUTHOR]

This paper proposes a simple mathematical model of non-stationary and non-linear stochastic dynamics, which approximates a (globally) non-stationary and non-linear stochastic process by its locally (or 'piecewise') stationary version. Profiting from the elegance and simplicity of both, the exact mathematical model referred to as the Ornstein–Uhlenbeck stochastic process (which is globally stationary, Markov and Gaussian) and of the Lyapunov criterion associated with the stability of stationarity, we show that the proposed non-linear non-stationary model provides a natural extension of the Onsager–Machlup theory of equilibrium thermal fluctuations, to the realm of non-stationary, non-linear and non-equilibrium processes. As an illustrative application, we then apply the extended non-equilibrium Onsager–Machlup theory, to the description of thermal fluctuations and irreversible relaxation processes in liquids, leading to the main exact equations employed to construct the non-equilibrium self-consistent generalised Langevin equation (NE-SCGLE) theory of irreversible processes in liquids. This generic theory has demonstrated that the most intriguing and long-unsolved questions of the glass and gel transitions are understood as a natural consequence of the second law of thermodynamics, enunciated in terms of the proposed piecewise stationary stochastic mathematical model. [ABSTRACT FROM AUTHOR]

This paper considers the exact solutions for plane shock waves in dilute polyatomic gases. The local enthalpy in the steady state plays an important role and fixes the Prandtl's number to write the temperature profile in an exact way. The condition for the Prandtl's number is a generalisation of Becker's result and now it considers the bulk viscosity. The velocity profile can also be found in an exact implicit way when the viscosity index is an arbitrary positive number. [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]

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]

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]

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.

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]

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]

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 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]

Self-diffusion along the longitudinal coordinate in a channel of varying cross section is considered. The starting point is the two-dimensional Enskog-Boltzmann-Lorentz kinetic equation with appropriated boundary conditions. It is integrated over the transversal coordinate to get an approximated one-dimensional kinetic equation, keeping the relevant properties of the original one. Then, a macroscopic equation for the time evolution of the longitudinal density is derived, by means of a modified Chapman-Enskog expansion method, that takes into account the inhomogeneity of the equilibrium longitudinal density. This transport equation has the form of the phenomenological Ficks-Jacobs equation, but with an effective diffusion coefficient that contains corrections associated to the variation of the slope of the equilibrium longitudinal density profile. [ABSTRACT FROM AUTHOR]

In the statistical mechanics approach to liquid-state theory, understanding the role of the intermolecular potential in determining thermodynamic and structural properties is crucial. The Fisher–Widom (FW) line, which separates regions in the temperature vs density plane where the decay of the total correlation function is monotonic or oscillatory, provides insights into the dominance of the attractive or repulsive part of the interactions. Stopper et al. have recently conjectured [J. Chem. Phys. 151, 014501 (2019)] that the line of vanishing excess isothermal compressibility approximates the FW line in simple fluids. Here, we investigate this conjecture using the Jagla potential and also explore the line of vanishing excess pressure. We employ theoretical approximations and Monte Carlo simulations to study one-dimensional and three-dimensional systems. While exact results for the one-dimensional case do not support the conjecture, our Monte Carlo simulations for the three-dimensional fluid validate it. Our findings not only contribute to the understanding of the relationship between the three transition lines but also provide valuable insights into the thermodynamic and structural behaviour of simple fluids. [ABSTRACT FROM AUTHOR]

Various hard body fluids are used as a reference term in molecular-based equations of state. Originally, these models were obtained either intuitively (as rigid geometrical objects) or by speculative physical considerations (e.g. pseudo-hard bodies). Considering a proper perturbation theory for molecular fluids, these n-site fused-hard-sphere models descend from the complex force field by a well-defined procedure but may also differ in dependence on the used additional approximations. As individual bodies, they are geometrical objects but their mutual interaction may be more complex including also non-additive hard sphere site-site interactions. The properties of such bodies may be expressed as a function of the number density, packing fraction or the overall excluded volume and these different scalings may also lead to even qualitatively different physical conclusions. This becomes particularly important when properties of different fluids are to be compared. This problem is discussed and exemplified by considering both convex body models and hard body models descending from realistic force fields with a specific focus on water and lower alcohols. [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]

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]

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 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]

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]