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

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

In molecular ro-vibrational calculations, it is desirable to build a symmetry-adapted basis set where both the rotational and vibrational functions are each separately symmetrised. Enabling rotational symmetrisation requires the use of body-fixed frames whose rotations under molecular symmetry operations are constant. The familiar Eckart and Sayvetz frames are examples of such frames, as are bisector frames for certain molecules. In this work, we introduce alternative frames for CH3Cl-type molecules and C2H6 that can be used for rotational symmetrisation. These are defined by the vibrational coordinates without the need for a reference geometry. We also provide one method to find such frames. Finally, we state a straightforward transformation of the s-vectors when changing frames which facilitates the evaluation of kinetic energy operators in these non-standard frames. [ABSTRACT FROM AUTHOR]

The Coupled-Cluster (CC) theory is one of the most successful high precision methods used to solve the stationary Schrödinger equation. In this article, we address the mathematical foundation of this theory with focus on the advances made in the past decade. Rather than solely relying on spectral gap assumptions (non-degeneracy of the ground state), we highlight the importance of coercivity assumptions – Gårding type inequalities – for the local uniqueness of the CC solution. Based on local strong monotonicity, different sufficient conditions for a local unique solution are suggested. One of the criteria assumes the relative smallness of the total cluster amplitudes (after possibly removing the single amplitudes) compared to the Gårding constants. In the extended CC theory the Lagrange multipliers are wave function parameters and, by means of the bivariational principle, we here derive a connection between the exact cluster amplitudes and the Lagrange multipliers. This relation might prove useful when determining the quality of a CC solution. Furthermore, the use of an Aubin–Nitsche duality type method in different CC approaches is discussed and contrasted with the bivariational principle. [ABSTRACT FROM AUTHOR]

This includes excited-state potentials along bond breaking coordinates, states dominated by two-electron transitions, and excited states of the same symmetry as the ground state, which are difficult to capture by conventional QMC techniques. B Winning article: I Accelerating convergence of equation-of-motion coupled-cluster computations using the semi-stochastic CC(P;Q) formalism i . b Stephen H. Yuwono B I et al. i b Molecular Physics B 118 b (19-20), Article: e1817592. This is particularly challenging when excited-state potentials along bond stretching coordinates and excited states dominated by two-electron transitions, i.e. situations that are often classified as multireference, are examined. [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 paper describes methods and fast computational algorithm for building effective Hamiltonians in molecular physics using perturbative approach. Separations of fast and slow variables are considered in the framework of contact transformations (CT). The particular focus is on a systematic derivation of effective models for rovibrational spectroscopy from ab initio-based potential energy surfaces with an exhaustive review of previous studies in this field. We consider applications to several types of polyads coupled by Fermi, Coriolis, Darling-Dennison and other types of resonance interactions with examples for asymmetric top, symmetric top and spherical top molecules. A flexible choice of the modelling operator accounts for strong couplings of various types of nuclear motion in molecules among closely lying levels including vibrational resonance schemes (2:1:2...), (2:1:2:1), (4:2:6:3), (3:2:1:2:1:1), etc. that occur for C2v, C3v and Td molecules and their isotopic species. The method is implemented in the MOL_CT programme suite, which offers a complementary tool to variational methods in terms of convergence and computational time. The range of applications is also different. The goal of the CT method is providing mathematical models for analyses of molecular spectra with the high-resolution accuracy using physically meaningful parameters derived from ab initio functions. [ABSTRACT FROM AUTHOR]

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

Calculating the underlying quantum behaviour of dense hydrogen has proven to be difficult due to subtle electronic effects and also the lightness of the proton leading to large quantum motion. The analytical form of the contribution from the nuclear and electronic degrees of freedom (DOF) is integrated out of the Schödinger equation by way of the generated pseudo pair potential in this paper. This is accomplished through the adiabatically linear response approximation of an electron gas-jellium model to the perturbations induced by discrete hydrogen ions in the absence of an external field. This pair potential for the hydrogen ions can then be fitted to generate first-principles data. From these pair potentials, computational time can be drastically reduced for larger systems of dense hydrogen to determine their various properties. [ABSTRACT FROM AUTHOR]

The reduction of CO2 into clean energy through electro catalytic technology provides a promising solution to alleviate energy shortages. In this paper, the graphitised material-supported metal dimer used for electro catalytic reduction of CO2 was proposed, and the reduction reaction mechanism was explored by density functional theory. The results indicate that the hydrogenation reduction of CO2 tends to occur preferentially, and it was found that improving the stability of catalyst structure can reduce the free energy of reaction and improve the adsorption effect of reactants, which significantly increase the conversion efficiency of CO2. The activation of CO2 on the catalyst surface is closely related to the binding of O atoms on the metal sites, the main reduction products and their reaction pathways were clarified. The reduction over potentials of CuCo-C, CuRh-C, CuZn-C and ZnCu-C were 0.915, 0.820, 0.774, and 0.354 V, respectively, thus ZnCu-C had a lower reduction over potential and higher catalytic efficiency. [ABSTRACT FROM AUTHOR]

We have addressed the aggregation phenomena of a cubic haematite particle suspension in an alternating magnetic field in order to investigate the regime change in the aggregate structure. Brownian dynamics simulations have been performed for a quasi-two-dimensional system with an alternating magnetic field applied in the plane of the system. In a weak alternating field, the cubic particles aggregate to form closely-packed structures tending to an aligned face-to-face configuration with increasing magnetic particle-particle interaction strength. In a closely-packed cluster, the orientation of the magnetic moment of a constituent particle tends to be more strongly influenced by the magnetic interaction between neighbouring particles and less influenced by the direction of the alternating magnetic field. As the strength of the applied field is increased, the particle moments become more restricted to the direction of the alternating field and the closely-packed structures transform into elongated aggregates with an offset face-to-face configuration. As the direction of the alternating magnetic field switches from the positive to the negative x-direction, the elongated aggregates tend to collapse temporarily and when the orientation of the moments is again strongly restricted to the switched field direction, elongated aggregate structures with offset face-to-face contact are re-formed in the system. Highlights of the present paper We have investigated a regime change in the internal structure of cubic particle aggregates in an alternating magnetic field. As the magnetic field strength is increased, closely-packed aggregates with an aligned face-to-face configuration transform into elongated aggregates with an offset face-to-face configuration. We have clarified that the elongated aggregates collapse temporarily and then re-form when the direction of the alternating magnetic field switches. We have suggested that the frequency of the magnetic field may be used as a means for controlling the local internal structure of particle aggregates. [ABSTRACT FROM AUTHOR]

Diversely functionalised pyrazolone analogues have been reported to display a wide range of biological activities. In this paper, we report the synthesis of a series of novel analogues based on piperidine fused pyrazolone core and explore its potential as novel antibacterial agents. The synthesised compounds were analysed using spectroscopic techniques such as 1H NMR, LC-MS, and FT-IR. The major highlight involves the cyclisation reaction of tert-butyl-4-methyl 3-oxopiperidine-1,4-dicarboxylate with the hydrazine component to access the privileged piperdine fused pyrazolone scaffold. This scaffold was further treated with HCl to remove the amine protecting group and subsequently reacted with acid chlorides to deliver the final products in excellent yields. Density functional theory (DFT) calculations were performed to determine the various molecular properties of the synthesised compounds. Based on the reactive sites explored by the molecular electrostatic potential maps, the compounds were screened against two gram positive bacterial strains namely S. aureus, and M. luteus, and a gram negative bacterial strain namely E.coli. Highlights A Series of novel pyrazole derivatives were synthesised using bicyclisation strategy. Computational methods were used to determine various quantum chemical properties. All molecules were screened against S. aureus, M. luteus, and E. coli bacterial strains. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated partial and total integral ionisation cross-sections of CF3Cl and CF2Cl2 molecules by a modified Jain-Khare semi-empirical approach during the direct and dissociative ionisation by electron impact. Present results show good agreement with the available data. Besides integral ionisation cross-sections, for the first time, we evaluated partial and total single differential cross sections for these molecules. No other results are available for single differential cross sections to compare the present calculated results. [ABSTRACT FROM AUTHOR]

In a recent paper, Díaz-Herrera et al. [Mol. Phys. 122, e1989071 (2022)] have studied the condensation transition of spherical droplets in finite closed systems using large-scale Molecular Dynamics simulations. The authors find that the loci of discontinuities in the observed pressure–density isotherms do not converge to the bulk orthobaric curve, apparently at odds with results obtained previously using Monte Carlo simulations. The purpose of this comment is to point out that the Monte Carlo and Molecular Dynamics simulation results are actually mutually consistent, and the apparent differences are not related to the different sizes studied, but to the way each method implements sampling of configuration space. [ABSTRACT FROM AUTHOR]

A comprehensive study of hole mobility in Germanium material dependence on strained substrate orientations and carrier transport directions was performed in this paper. The heavy hole, light hole, and spin–orbit bands are included in the calculation of valence band structure. The biaxial strain induced valence band edge energy splitting and effective mass change were evaluated as well as their impacts on the hole mobility in Germanium were analysed. The results show that the optimum strained substrate orientation and carrier transport direction configuration are biaxial compressive strained on the (110) oriented substrate and in-plane [ 1 ¯ 10 ] as a hole transport direction, the configuration of which has the maximum hole mobility under the same strained level in comparison with others. The reason for high hole mobility is also explored. The current research is helpful to design the high performances p-channel MOSFETs in the strained Germanium system. The hole mobility of Germanium versus strain level under different biaxial strained substrate and transport directions configurations [ABSTRACT FROM AUTHOR]

This paper describes a collaboration between Professor Ernest Davidson and the author, which began in 1976 and lasted until Ernest left the University of Washington in 1984. During those 9 years we co-authored a total of 34 papers that described the results of ab initio calculations on a variety of different types of organic molecules, These included antiaromatic annulenes, carbanions, carbenes, conjugated radicals and radical cations, and nonKeklé hydrocarbon diradicals. Our collaboration led to insights about symmetry breaking, both real and artefactual, which formed the basis for a frequently-cited review article on this subject that we co-authored. However, our most often-referenced paper was concerned with predicting the sizes and signs of the singlet-triplet splittings in diradicals, based on whether or not the non-bonding Hückel molecular orbitals of a diradical can be chosen so that they are confined to disjoint sets of atoms. In 1984, we co-authored a paper on the Cope rearrangement. Since then, we have both continued to publish papers on this interesting reaction, but independently, rather than together. The results of the calculations that we each performed on the Cope rearrangement and how this reaction is affected by radical-stabilizing substituents are described. Our independent discoveries, that calculations beyond the CASSCF level are necessary in order to describe correctly the transition structure for the Cope rearrangement, led to our most recent joint publication, a 1996 review on the general importance of including dynamic correlation in ab initio calculations. [ABSTRACT FROM AUTHOR]

A theoretical investigation on oxidation reaction of ethyl vinyl ether (EVE) and.Cl are carried out in this paper. By employing M06-2x/6-31 + g(d,p)//6-311++g(3df,2p) method, complex reaction mechanisms are assumed on the basis of thermodynamic data. All the.Cl-addition reactions are dominant channels. The corresponding major products, such as ethyl formate, acetaldehyde and several chloro compounds, are generated from.Cl-addition to double bond of EVE. These products play an important role in the formation of secondary organic aerosol. By employing MESMER grogram, rate coefficients of the primary reactions are computed in the temperature range of 200–400 K and the pressure range of 500–2000 Torr. Combined with the kinetic data and temperature, an Arrhenius equation is fitted as kEVE+Cl = 1.54 × 10−10 exp (121.9/T). Also, the rate constant at 298 K and 760 Torr is calculated to be 2.17 × 10−10 cm3 molecule−1 s−1. Furthermore, the atmospheric lifetime of EVE with respect to.Cl is estimated to be 4.3–11.9 h in different regions. The short lifetime indicates that ·Cl-initiated oxidation is competitive in the degradation of EVE in some special areas. This work could confirm the experimental investigation and serve as the supplement of our previous theoretical studies. [ABSTRACT FROM AUTHOR]

Theoretical line shifts of nitrogen dioxide lines induced by air are reported at the room temperature (296 K). Calculations are performed for ∼31500 lines in the spectral range of 5700–7500 cm−1 for the ν 1 + 3 ν 3 , ν 1 + 4 ν 3 , 2 ν 1 + 3 ν 2 + ν 3 , 3 ν 1 + ν 2 + ν 3 , 2 ν 2 + 3 ν 3 and 4 ν 3 bands including rotational quantum numbers up to N = 87 and K a = 20. The data have been evaluated theoretically by a semi-empirical method which is based on the impact theory of broadening and includes the correction factors whose parameters can be determined by fitting the shift coefficients to the experimental data. Nitrogen dioxide plays an important role in the Earth's tropospheric and stratospheric photochemistry, it is one of the most common anthropogenic substances emitted into the atmosphere. Nitrogen dioxide is involved in the production and destruction of ozone. The infra-red high resolution spectra of NO2 are the subject of intense interest during recent years. Obtained results are implemented in spectroscopic databases aimed at atmospheric applications such as HITRAN and GEISA. As to the line shift parameters, there are few papers. In this work, theoretical NO2-line shifts induced by air are reported for many lines. [ABSTRACT FROM AUTHOR]

InN monolayer with graphene-like morphology and desirable electronic property is a promising candidate for gas sensing application. In this paper, we study the adsorption and sensing performances of the Rh-decorated InN (Rh–InN) monolayer upon two typical dissolved gases in the transformers oil, namely H2 and C2H2, to explore its potential to evaluate the working condition of the transformers. Rh atom conducts n-doping on the pristine InN surface with Eb of −2.01 eV. Also, chemisorption is determined for H2 and C2H2 adsorption on the Rh–InN surface given that the Ead of −0.88 and −2.15 eV, respectively. The opposite changing trend of Eg in H2 and C2H2 systems manifests the resistance-based sensing mechanism for selective detection of two gas species. The applied electric field supports the work function analysis that an Rh–InN monolayer possesses a strong potential for field-effect transistor sensor application in terms of H2 and C2H2 detection, wherein the charge-transfer in the gas systems is tunable by altering the voltage. Moreover, the excessive electric field is not considered to be suggestible since it can impact the geometric stability of the Rh–InN monolayer. This theoretical work is meaningful to exploit novel sensing 2D materials to guarantee the good operation of the power system. Highlights Rh-decorating behaviors upon InN monolayer is studied. Expound the potential of Rh-InN monolayer for dissolved gas analysis in transformers. Analyze the effect of applied electric field on gas adsorptions. [ABSTRACT FROM AUTHOR]

This paper represents careful quantum-mechanical investigation with further generalization of the novel transformation mechanisms for the wobble G·T(wWC) and reverse wobble G·T(rwWC) base pairs into the classical Watson–Crick-like G*·T(WC) base pair, obtained at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory in vacuum under normal conditions (T = 298.15 K). These G·T(wWC)↔G·T*(WC)↔G*·T(WC), G·T(wWC)↔G·T*O2(rWC)↔G+·T−(rWC)↔G*·T(rWC)↔G*·T(WC), G·T(rwWC)↔G*·T(rWC)↔G*·T(WC) and G·T(rwWC)↔G·T*(WC)↔G*·T(WC) conformationally-tautomeric reactions are determined by the sequential proton transfer inside the base pair, shifting of the G and T DNA bases relatively each other and cis↔trans changing of their mutual orientation. The main intrigue of the presented results is that two different G·T(wWC)↔G·T*(WC)↔G*·T(WC) and G·T(rwWC)↔G*·T(rWC)↔G*·T(WC) routes guarantee almost the same probability of the acquisition by the wobble G·T(wWC) and reverse wobble G·T(rwWC) base pairs of the G*·T(WC) Watson–Crick-like configuration. Notably, that reverse wobble G·T(rwWC) and reverse Watson–Crick G·T*O2(rWC) base pairs tautomerise via the double proton transfer along the intermolecular H-bonds – G·T(rwWC)↔G*·T*(rwWC) and G·T*O2(rWC)↔G+·T−(rWC)↔G*·T(rWC), respectively. It was also considered conformational mobility of the G·T*(WC), G·T*O2(rWC), G·T(wWC), G·T(rwWC), G*·T*(rwWC) and G*·T(rWC) base pairs through the mutual rotation of the bases around the intermolecular H-bond. Methods of the structural bioinformatics have been used for indication of the G·T base pairs in real biological systems. Revealed conformationally-tautomeric transformations can explain transitions of the DNA molecule from parallel to anti-parallel conformations and vice versa. [ABSTRACT FROM AUTHOR]

The article reports that a new prize named the Molecular Physics Longuet-Higgins Young Author's Prize has been started by the editors of the journal "Molecular Physics." The award, having a prize money of 1000 U.S. dollars, will be given to a writer who has made a significant contribution to a top quality paper published in the journal during 2009, as judged by the editors. Information on Christopher Longuet-Higgins, co-founding editor of journal is also provided.

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al6OMm (M = Na, K; m = 2,4,6) and a few other AlnXNam (X = C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s2p6 shell closure, and the antibonding orbitals make the metal moieties form closed 2S22P6 shells. The 26 valence electrons form closed s2p6S2P6D10 shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al6O2− core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals. [ABSTRACT FROM AUTHOR]

Copolymer inhibitor with multifunctional groups has a good effect on inhibiting the secondary reaction in the clinker leaching process for alumina production, but the inhibition mechanism of the copolymer is not clear yet. In this paper, molecular dynamics simulation was used to study the adsorption process of the copolymer inhibitor with multifunctional groups, such as acrylic acid-vinyl alcohol copolymer (PAV) and acrylic acid-hydroxypropyl acrylate copolymer (PAH), on the β-dicalcium silicate (C2S) crystal surface, and reveal its inhibiting mechanism. Meanwhile, the polyacrylic acid (PAA) with only the carboxyl group also is simulated for comparing the inhibition effect with copolymer inhibitors. The results show that the binding energy between copolymer (PAV, PAH) and β-C2S is greater than that of PAA with a single functional group. The order of binding energy is as follows: PAH > PAV > PAA. In aqueous solution, the water molecule can restrict the degree of deformation of polymers, increase the distance between polymers and β-C2S and then lead to weakening of the adsorption of polymers on the crystal surface. The comprehensive and coordination effect of carboxyl and hydroxyl functional groups in PAV and PAH can strengthen the adsorption of copolymers on the β-C2S surface. The different spatial distribution of multifunctional groups in the molecular structure has a different influence on the adsorption of the copolymer. The results can provide a theoretical basis for researching new and highly effective copolymer inhibitors with multifunctional groups. Compared the adsorption state: The comprehensive and coordinate action of carboxyl and hydroxyl groups of the inhibitor with multifunctional groups make the inhibitor have a stronger adsorption ability on the surface of β-C2S than that with a single functional group. The results obtained in this paper can provide a theoretical basis for the research and development of new and highly effective polymeric inhibitors with multifunctional groups. Highlights The interaction between copolymer and β-C2S was investigated by MD simulation. The binding energy order between polymers and β-C2S is PAH > PAV > PAA. The presence of water molecules can weaken the adsorption of the copolymer on the surface of β-C2S. The comprehensive and coordinate action of carboxyl and hydroxyl groups of the inhibitor with multifunctional groups make the inhibitor have a stronger adsorption ability on the surface of β-C2S than that with a single functional group. [ABSTRACT FROM AUTHOR]

The AC component of drying agent described in literature 6 can be injected into tight gas reservoir formation to reduce original and residual water saturation caused by completion and stimulation. However, the pore and throat of formation in tight gas reservoir are so small that AC particles are difficult to be injected into them directly. Through experiments, we discovered that a certain amount of AC could dissolve in supercritical carbon dioxide (SCCO2) and it could separate out from SCCO2 when pressure decreased. Therefore, SCCO2 can be used as transport agent and bring it into tight gas reservoir for drying formation. We further study the solubility of AC in SCCO2 under different temperature and pressure, and also screen solubilizer to enhance the solubility in this paper. The results show that the solubility of AC in SCCO2 is 0.0005 mol/mol at 40°C and 8 MPa. When temperature is constant, the solubility of AC in SCCO2 increases with the increase of pressure, but the impact of temperature on the solubility shows different variation principle with pressure increasing. In addition, ethyl alcohol is the best solubilizer for increasing the solubility of AC in SCCO2, and the optimal concentration of solubilizer in SCCO2 is 10%. [ABSTRACT FROM AUTHOR]

Problems involving quantum impurities, in which one or a few particles are interacting with a macroscopic environment, represent a pervasive paradigm, spanning across atomic, molecular, and condensed-matter physics. In this paper we introduce new variational approaches to quantum impurities and apply them to the Fröhlich polaron – a quasiparticle formed out of an electron (or other point-like impurity) in a polar medium, and to the angulon – a quasiparticle formed out of a rotating molecule in a bosonic bath. We benchmark these approaches against established theories, evaluating their accuracy as a function of the impurity-bath coupling. [ABSTRACT FROM AUTHOR]

Novel ways to reduce the computational effort for atomic structure prediction while retaining high accuracy are of wide interest. This paper describes an implementation of the method of averaging over the wave vector k for the description of the lithium condensation. We show that the direct transition from the gas phase to the crystalline one is complicated. The formation of the crystal structure occurs through the condensation of individual small clusters. [ABSTRACT FROM AUTHOR]

Some models were developed for the interpretation of infrared intensities based on the distribution of molecular charge and its mobility during atomic displacement. The objective of this paper is to apply NPA charges in the C-CF-O model to obtain the dipole moment derivatives and infrared intensities of AH3, X2CY and some linear molecules. In all cases analyzed, the NC-NCF-O model was more accurate than the reference model Charge – Charge Flux – Dipole Flux (C–CF–DF). Furthermore, the computational cost of obtaining NPA charges and their respective flux are much lower than those obtained by more complex models. This allows a greater application for large molecules. [ABSTRACT FROM AUTHOR]

In this paper, Scarf II potential is used to construct the improved Scarf II potential energy function (ISPEF) for applications to diatomic molecules. Conditions to be satisfied by a diatomic molecule potential are applied in the derivation of potential parameters of the ISPEF. Equation of bound state ro-vibrational energies is obtained for the ISPEF via a Pekeris-type approximation to the centrifugal term of the Schrödinger equation. The ISPEF and expression for eigen energies are used to model spectroscopic data of five diatomic molecules: N 2 + ( X 1 ∑ g +) , Na2 (c1 Πu), ScI (B1 Π), NaK (c3 Σ+) and CO (X1 Σ+). Average absolute deviation from dissociation energy (AAD) and mean absolute percentage deviation from Rydberg-Klein-Rees data (MAPD) are used to analyse data. On the basis of AAD as goodness-of-fit index, the ISPEF represents a near-perfect model for the diatomic molecules analysed and also a better model than the existing literature data of improved Tietz potential for the Na2 (c1 Πu) molecule. On the other hand, with the MAPD as goodness-of-fit index, the available literature results show that eigen energies of ISPEF are equivalent to ro-vibrational energies of Morse and improved generalised Pöschl-Teller potentials in fitting spectroscopic data of CO (X1 Σ+) molecule. [ABSTRACT FROM AUTHOR]

Building on our previous work on NO + Ar, this paper presents a complete set of orientation measurements and quantum mechanical calculations for the NO + Kr collision system, including both spin-orbit conserving and changing collisions, and both side-on (x-axis) and end-on (z-axis) orientations. While many of the trends observed in the oriented differential and integral scattering distributions, as well as in the spin-orbit branching fractions, are similar to the ones seen previously for NO + Ar, a direct comparison with the Ar data reveals subtle differences in the scattering dynamics, which we rationalise with the more extended attractive regions on the NO + Kr potential energy surfaces. High-impact parameter collisions that lead to low scattering angles in the spin-orbit conserving manifold are particularly sensitive to the topology in the attractive parts of the potential, whereas more impulsive, low-impact parameter trajectories, which sample the repulsive parts of the potential, produce very similar features in the oriented differential cross sections for the Ar and Kr systems, especially for spin-orbit changing collisions. [ABSTRACT FROM AUTHOR]

Lutoslaw Wolniewicz has spent two or three months each summer from 1976 to 1994 as guest of Kurt Dressler in Zurich to use the Computer Centre of the ETH for ab-initio calculations of rovibronic energies and transition moments in the hydrogen molecule. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the impact of using a frequency-dependent embedding potential in quantum chemical embedding calculations of response properties. We show that the introduction of a frequency-dependent embedding potential leads to further model complications upon solving the central equations defining specific molecular properties. On the other hand, we also show from a numerical point of view that the consequences of using such a frequency-dependent embedding potential is almost negligible. Thus, for the kind of systems and processes studied in this paper the general recommendation is to use frequency-independent embedding potentials since this leads to less complicated model issues. However, larger effects are expected if the absorption bands of the environment are closer to that of the region treated using quantum mechanics. [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]

Since in coupled-cluster (CC) theory, ground-state and excitation energies are eigenvalues of a non-Hermitian matrix, these energies can in principle take on complex values. In this paper, we discuss the appearance of complex energy values in CC calculations from a mathematical perspective. We analyse the behaviour of the eigenvalues of Hermitian matrices that are perturbed (in a non-Hermitian manner) by a real parameter. Based on these results, we show that for CC calculations with real-valued Hamiltonian matrices the ground-state energy generally takes a real value. Furthermore, we show that in the case of real-valued Hamiltonian matrices complex excitation energies only occur in the context of conical intersections. In such a case, unphysical consequences are encountered such as a wrong dimension of the intersection seam, large numerical deviations from full configuration-interaction (FCI) results close to the conical intersection, and the square-root-like behaviour of the potential surfaces near the conical intersection. In the case of CC calculations with complex-valued Hamiltonian matrix elements, it turns out that complex energy values are to be expected for ground and excited states when no symmetry is present. We confirm the occurrence of complex energies by sample calculations using a six-state model and by CC calculations for the H 2 O molecule in a strong magnetic field. We furthermore show that symmetry can prevent the occurrence of complex energy values. Lastly, we demonstrate that in case of complex Hamiltonians the real part of the complex energy value provides a very good approximation to the FCI energy. [ABSTRACT FROM AUTHOR]

This paper aims to present some features of the non-Poissonian statistics of the spread of a disease like COVID19 to a community of chemical-physicists, who are more used to particle-based models. We highlight some of the reasons why creating a 'transferable' model for an epidemic is harder than creating a transferable model for molecular simulations. We describe a simple model to illustrate the large effect of decreasing the number of social contacts on the suppression of outbreaks of an infectious disease. Although we do not aim to model the COVID19 pandemic, we choose model parameter values that are not unrealistic for COVID19. We hope to provide some intuitive insight in the role of social distancing. As our calculations are almost analytical, they allow us to understand some of the key factors influencing the spread of a disease. We argue that social distancing is particularly powerful for diseases that have a fat tail in the number of infected persons per primary case. Our results illustrate that a 'bad' feature of the COVID19 pandemic, namely that super-spreading events are important for its spread, could make it particularly sensitive to truncating the number of social contacts. [ABSTRACT FROM AUTHOR]

Extended phase-space isokinetic methods in their deterministic [Minary et al., Phys. Rev. Lett. 93, 150201 (2004)] and stochastic forms [Leimkuhler et al., Mol. Phys. 111, 3579 (2013)] have proved tremendously successful in allowing multiple time-scale molecular dynamics simulations to be performed with very large time steps. These methods work by coupling the physical degrees of freedom to a set of Nosé-Hoover chain or Nosé-Hoover Langevin thermostats via an isokinetic constraint, which has the effect of avoiding resonance artifacts that plague multiple time-step algorithms. In this paper, we introduce a new resonance-free approach that achieves the same gains in time step but without the imposition of isokinetic constraints or the introduction of extended phase-space variables. Rather, we modify the physical Hamiltonian that effects the same regulation of resonances achieved by the isokinetic constraints. In so doing, we show that sampling errors can be controlled and performance improvements are possible within a simpler Hamiltonian framework. The method is demonstrated in simulations of the structure of liquid water and, in conjunction with enhanced sampling, in generation of the Ramachandran free-energy surface of the solvated alanine dipeptide. [ABSTRACT FROM AUTHOR]

This paper presents a unified model of gas phase acetone photophysics and photochemistry that is based on experimental data, which are reviewed and discussed in detail, and a detailed microcanonical master equation formulation. The model accounts for experimental measurements in molecular beams as well as in thermal systems, leads to a new interpretation of some experiments, and reveals a fundamental property of quantum yield measurements that are relevant to atmospheric chemistry. It also furnishes a platform for future theoretical and experimental developments. [ABSTRACT FROM AUTHOR]

Many of these papers build, directly or indirectly, on the work of Lutek, reflecting his influence on our field and serving as a testament to his lasting contributions to molecular physics and to quantum chemistry. This Special Issue of Molecular Physics is dedicated to the memory of Professor Lutoslaw (Lutek) Wolniewicz, our friend and teacher, an initiator of rigorous thinking in quantum chemistry. We are proud and delighted to present this Special Issue of Molecular Physics, comprising 31 articles submitted by friends, coworkers, and followers of Lutek Wolniewicz. [Extracted from the article]

In previous papers we proved that the geometrical elements of the wave described by the Schrodinger equation, namely the wave surfaces and their normals, denoted by C curves, are solutions of the Hamilton-Jacobi equations, written for the same system, in the case of stationary systems. The C curves correspond to the same constants of motion as the eigenvalues of the Schrodinger equation. In two recent papers we presented a central field method for the calculation of the C curves, and of the corresponding energetic values. The method was verified for the atoms He, Li, Be, B, C, N and O. In this paper we extend this method, using the symmetry properties of the systems, in the case of the diatomic molecules, with exemplification for Li2, Be2, B2, C2, LiH, BeH, BH and CH. The accuracy of the method is, as in the case of the atoms, comparable to the accuracy of the Hartree-Fock method, for the same system. This could be a potential useful result, because our approach predicts also basic properties of the molecules in discussion. [ABSTRACT FROM AUTHOR]

The present paper deals with the correlation between intramolecular and intermolecular interactions of polycarboxybetaines. The degree of coupling between the opposite charges within the polycarboxybetaine molecules was varied by spacers of different length and by the substitution of additional alkyl chains at the quaternary nitrogen atom. In order to check intermolecular interactions between polycarboxybetaines, SANS measurements were carried out at aqueous polycarboxybetaines solutions. For getting information about the interaction with an oppositely charged polyelectrolyte, multilayers were formed by alternating adsorption of polystyrene sulfonate (PSS) and polycarboxybetaines from aqueous solutions. The occurrence of a structure peak in SANS spectra and the ability to form polyelectrolyte multilayers provide an indicator for the polyelectrolyte character of some of the studied polycarboxybetaines. Not only the charge but also the hydrophobicity of the polycarboxybetaines has a pronounced effect on the chain conformation and therefore on the thickness of the polyelectrolyte multilayers. The results show that small differences in molecular architecture lead to pronounced differences in intermolecular interactions. [ABSTRACT FROM AUTHOR]

In this paper, the formalism describing the spontaneous emission rate of an excited molecule (or atom) with definite transition electric dipole moment, in vicinity of a perfect conductive wall is developed. Separately, for molecules (or atoms) with the electric dipole moment parallel and perpendicular to the wall, the spontaneous emission rate of the molecule is calculated in two ways: (1) by using the explicit form of the vector potential operator in the Fermi' golden rule and taking the expectation value in vacuum state and (2) by considering the relation between the spontaneous emission rate and the vector potential Green function, and calculating the required Green function components of the space at the presence of a perfect conductive wall. The two methods yield the same expression for the spontaneous emission rate. The agreement of the results with some previous works is shown and the variations of the spontaneous emission rate for each dipole moment orientation are demonstrated. [ABSTRACT FROM AUTHOR]

This paper reports on the differential, integral, momentum transfer and viscosity cross sections along with spin polarisation for elastically scattered electrons and positrons from iron atoms in the incident energy ( E i ) range 1 ≤ E i ≤ 10 4 eV. In addition, we report here systematically the details of the critical minima in the elastic differential cross sections, and the absorption and total cross sections. An optical model using a complex optical potential, composed of static, exchange, polarisation and imaginary terms, is used to solve the Dirac relativistic equation in partial-wave analysis. A comparison of our evaluated cross sections with the available experimental data and other theoretical findings shows a reasonable agreement over the studied energy range. [ABSTRACT FROM AUTHOR]

The modular path integral (MPI) formulation offers a numerically exact, versatile, and highly efficient approach to the quantum dynamics of extended systems characterised by a single-file arrangement of units with short-range interactions, such as hydrocarbons, molecular aggregates with exciton couplings, or spin chains. Rather than propagating the many-particle wavefunction or density matrix in time in the usual stepwise fashion, the MPI scheme proceeds by sequentially integrating over each unit after linking its quantum paths to those of its neighbour and leads to linear scaling with system length. This paper shows that the linking matrix can be further decomposed into a diagonal matrix and a product of low-dimensional matrices, which can be applied sequentially. This factorisation changes the cost scaling from L2 to L log ⁡ L , where L is the number of quantum paths, leading to dramatic savings that are analogous to those attained by the fast Fourier transform algorithm and allowing application of the MPI procedure to systems with larger units and to longer propagation times. Applications to spin chains and to electron-vibration dynamics in a large molecular aggregate illustrate the efficiency of the algorithm. [ABSTRACT FROM AUTHOR]

In this paper, Rh-doped S-vacancy PtS2 (Rh-PtS2) monolayer is proposed as a novel sensing material for SOF2 detection in order to evaluate the operation status of SF6 insulation devices. The Rh dopant is stably anchored on the S-vacancy of the PtS2 surface with the binding force (Eb) of −4.65 eV. The Rh-PtS2 monolayer behaves as chemisorption upon SOF2 adsorption with adsorption energy (Ead) of −1.08 eV, and the presence of humidity would weaken such adsorption performance, reducing the Ead to −0.82 eV instead. The band structure (BS) analysis implies that the existence of humidity causes cross-sensitivity for the Rh-PtS2 monolayer as the resistance-type sensor, while the optical property analysis indicates the little impact of humidity for that as an optical nano-sensor upon SOF2 detection. Besides, the charge-transfer (QT) in SOF2 adsorption is adjustable via modulating the applied electric strength, giving rise to the tunable and admirable sensing response upon SOF2 sensing with a Rh-PtS2 monolayer based field-effect transistor sensor. Our calculations are meaningful to explore a novel sensing material for SOF2 detection in order to realise the operation status evaluation in SF6 insulation devices. [ABSTRACT FROM AUTHOR]

Orientation arrangement of hydration shells for hydrated cation plays an important role in solid–liquid interfaces. However, there is still poor understanding about the structure of the hydration shells formed at the solid–liquid interface. In this paper, we study the structures and interaction of typical hydrated alkali metal cation (Li+, Na+ and K+) on the flat polar material surface of the hexagonal boron nitride (h-BN) sheet by increasing the number of water molecules from n = 1 to n = 9 through the artificial bee colony (ABC) algorithm and density functional theory calculations. The hydration shell around alkali metal cation could be divided into two groups, one is Li+-(H2O)n and Na+-(H2O)n and the other is K+-(H2O)n. The orientation of hydration shell for K+-(H2O)n complexes exhibits stronger anisotropy behaviour than both Li+-(H2O)n and Na+-(H2O)n complexes on the h-BN sheet. It is found that the stronger orientation anisotropy of K+-(H2O)n originates from the weak cation-hydration energy and its weak influence upon the π-K+ interaction. Our findings provide valuable insights into the microscopic details of the structures and adsorption of hydrated cation on the h-BN sheet. [ABSTRACT FROM AUTHOR]

In this paper, we report vibrational energy levels of some tetraphenylporphyrins and its cation radicals, i.e. Cu[TPP], Cu[TPP]+, Ni(TPP), Ni(TPP)+, ClFe(TPP) and ClFe(TPP)+using U(2) algebraic model Hamiltonian. In our study, we have used five fitting parameters which provide better comparisons between the experimental and theoretical calculations throughout the study. RMS deviation has been improved in this paper due to the inclusion of intermode couplings in algebraic model. Structure of metalloporphyrins In our work, we study the spectroscopic features of some biomolecules using Lie algebraic methods. This will be sought to be accomplished by studying the different vibrational energy levels as function of vibrational quantum numbers for certain biomolecules. Possibilities of local-to-normal transition in viable cases will be taken into consideration. In addition, new vibrational parameters for certain biomolecules will be sought to be identified for cases where Lie algebraic approach has not been initiated. The Lie algebraic study may as well be useful in interpreting the vibrational spectra of proteins and other biological systems. [ABSTRACT FROM AUTHOR]

High resolution molecular spectroscopy often pushes theoretical methods to their limits. Electrons in molecules usually respond adiabatically to the much slower motion of nuclei, but this approximation breaks down when molecules have degenerate ground or closely spaced electronic states. B Winning article: b Vibronic mean-field and perturbation theory for Jahn-Teller and pseudo-Jahn-Teller molecules. [Extracted from the article]