Search

The quantity given for a square integrable wavefunction ψ allows one to define very different kinds of measurables, such as absorption spectrum (as a Fourier transform (FT) over for t=0) as well as high-order harmonic generation (HHG) spectrum (as a FT over t for). The main objective of this paper is to define this quantity based on a spectral decomposition of ψ to non-Hermitian wavefunctions obtained in complex scaling calculations. The obtained formal expression combines matrix elements based on the non-Hermitian c-inner product, as expected, and surprisingly also Cartesian (Euclidean) norms and overlaps of complex scaled wavefunctions. The latter feature diminishes in cases such as absorption spectra, however, it does take place in expressions obtained for the HHG spectrum. The exact non-Hermitian formalism is necessary for theoretical calculations of HHG at coupled photoionisation resonances, illustrated here for a multiphoton conversion in helium atom near a conical intersection. [ABSTRACT FROM AUTHOR]

Spontaneous emission (SE) is usually studied within the framework of quantum dissipation theory. In this paper we pursue a different view of SE. Namely, we take advantage of Nonhermitian Quantum Mechanics (NHQM) and interpret SE as the decay of a Feshbach type resonance. Correspondingly, we aim at calculating the SE decay rate Γ (resonance width) and the associated resonance wavefunction via the complex scaling (CS) method. Standard application of CS in NHQM is based on scaling the dissociative coordinates of the system,. In the case of SE, the decay consists in emitting photons. Therefore the CS must be applied on (suitably defined) position coordinates of the photons. Feasibility of such a programme is demonstrated explicitly through choosing the adequate photon coordinates and performing CS of the photon wavefunctions in the position representation. It is anticipated in this way that CS makes the full resonance wavefunction square integrable, and enables thus the calculation of Γ by proceeding in complete analogy with the well established NHQM approaches. As an illustration, the standard Golden Rule formula for Γ is rederived from the CS nonhermitian perturbation theory. [ABSTRACT FROM AUTHOR]

In this paper, using Fourier transform infrared (FTIR) spectroscopy, ion conductivity measurements and first-principle density functional theory (DFT) calculations, we study intermolecular interactions between three molecules (methyl tetrahydrophthalic anhydride (MeTHPA), succinonitrile (SN) plastic crystal, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt) constituting the lithium-ion battery electrolyte. The C–O stretching band position in MeTHPA shifts to a lower frequency in the order of MeTHPA–SN < MeTHPA < MeTHPA–LiTFSI/SN < MeTHPA–LiTFSI; the average C–O bond length in MeTHPA increases in the same order, which reveals the linear correlation between the vibration frequency shift and bond length change. Furthermore, the lithium ionic conductivities of MeTHPA–LiTFSI/SN and MeTHPA–LiTFSI are consistent with this linear relationship, which confirms that the bond length, vibration frequency and lithium-ion transport are strongly influenced by molecular-level interactions. Our results provide fundamental insights valuable for the understanding of the effect of intermolecular interactions on molecular geometry and physical quantities in different electrolytes, and could be utilized to guide the design of high-performance electrolyte materials. [ABSTRACT FROM AUTHOR]

Oxidative decomposition of solid lithium peroxide is an important part of the charging process in a Li-O2 battery. In this paper, we investigate oxidative decomposition mechanisms of lithium peroxide clusters as molecular models for solid lithium peroxide using density functional methods to understand charging processes in advanced energy storage systems. Most calculations are done using a (Li2O2)4 cluster with similar results obtained from a larger (Li2O2)16 cluster. Reaction pathways of the clusters involving different sequences of oxidation, oxygen evolution, lithium cation removal, and spin excitation are investigated. The computations suggest that certain oxidative decomposition routes may not have dependence on the oxygen evolution or Li-ion removal kinetics due to the exothermicity of oxygen removal and Li+ removal (by solvent) upon oxidation. The computed charge potentials evaluated using a tetramer model indicates that it is possible to have low overcharge potential provided there exists a good electronic conductivity to facilitate the oxidative decomposition. Finally, oxidation potentials of a series of LixOy clusters are investigated to assess their dependence on stoichiometry and how the local site from which the electrons are being removed affects the charge potentials. [ABSTRACT FROM AUTHOR]

Quadrupole relaxation enhancement (QRE) has been suggested as the key mechanism for a novel class of field-selective, potentially responsive magnetic resonance imaging contrast agents. In previous publications, QRE has been confirmed for solid compounds containing 209Bi as the quadrupolar nucleus (QN). For QRE to be effective in aqueous dispersions, several conditions must be met, i.e. high transition probability of the QN at the 1H Larmor frequency, water exchange with the bulk and comparatively slow motion of the Bi-carrying particles. In this paper, the potential influence of structural order within the compounds ('crystallinity') on QRE was studied by nuclear quadrupole resonance (NQR) spectroscopy in one crystalline and two amorphous preparations of Triphenylbismuth (BiPh3). The amorphous preparations comprised (1) a shock-frozen melt and (2) a granulate of polystyrene which contained homogeneously distributed BiPh3 after common dissolution in THF and subsequent evaporation of the solvent. In contrast to the crystalline powder which exhibits strong, narrow NQR peaks the amorphous preparations did not reveal any NQR signals above the noise floor. From these findings, we conclude that the amorphous state leads to a significant spectral peak broadening and that for efficient QRE in potential contrast agents structures with a high degree of order (near crystalline) are required. [ABSTRACT FROM AUTHOR]

The confined dynamics of water molecules inside a pore involves an intermittence between adsorption steps near the interface and surface diffusion and excursions in the pore network. Depending on the strength of the interaction in the layer(s) close to the surface and the dynamical confinement of the distal bulk liquid, exchange dynamics can vary significantly. The average time spent in the surface proximal region (also called the adsorption layer) between a first entry and a consecutive exit allows estimating the level of 'nanowettablity' of water. As shown in several seminal works, NMRD is an efficient experimental method to follow such intermittent dynamics close to an interface. In this paper, the intermittent dynamics of a confined fluid inside nanoporous materials is discussed. Special attention is devoted to the interplay between bulk diffusion, adsorption and surface diffusion on curved pore interfaces. Considering the nano or meso length scale confinement of the pore network, an analytical model for calculating the inter-dipolar spin-lattice relaxation dispersion curves is proposed. In the low-frequency regime (50 KHz-100 MHz), this model is successfully compared with numerical simulations performed using a 3D-off lattice reconstruction of Vycor glass. Comparison with experimental data available in the literature is finally discussed. [ABSTRACT FROM AUTHOR]

In this paper, two information-based functions are employed as a real space measure of the Fermi and Coulomb holes for same-spin electrons. The first one is the information content of the Exchange-Correlation hole, calculated from the Kullback-Leibler divergence of the same-spin conditional pair density respect to the marginal probability (). As reported previously, , can be used to reveal the regions of the space associated to the classical electron pair model. Here, correlated wave-functions, such as CISD, MP2, and CCSD, are considered for the calculation of . This is achieved by introducing an approximated method based on employing natural orbitals and their occupancy numbers. In addition to , in this work we propose a measure of the information content of the same-spin correlation hole, which is computed in terms of the Kullback-Leibler divergence of a correlated same-spin conditional pair density respect to the uncorrelated Hartree-Fock pair density (). The proposed methodology is discussed in the light of the result derived from noble gas atoms, the molecule and some non-covalently bonded systems. [ABSTRACT FROM AUTHOR]

Inverted perovskite solar cells (PSCs) have attracted much attention due to their low-temperature and solution-based process. Electron transport layers are important components in inverted PSCs. Non-fullerene n-type organic small molecules seem to be more attractive as electron transport layers, because their structures are easy to be synthesised and modified. In this paper, density functional theory and semi-classical Marcus electron transfer theory were used to explore the electron transport properties in three azaacene derivatives, including one experimentally reported molecule, 1,4,9,16-tetrakis((triisopropylsilyl)ethynyl)quinoxalino[2‴,3‴:4″,5″]cyclopenta[1″,2″,3″:5′,6′]acenaphtho[1′,2′:5,6]pyrazino[2,3-b]phenazine (1), and two theoretically designed molecules (2 and 3). Compound 2 is formed by substituting i-Pr groups in compound 1 with H atoms, which is designed to evaluate the effect of i-Pr groups on the electron transport properties. Compound 3 is designed by adding one more benzopyrazine group to the conjugation structure of compound 1. It shows that i-Pr group can increase HOMO and LUMO energy levels and improve solubility in organic solvent and hydrophobicity. Enlarging conjugation can not only decrease LUMO energy level and electron reorganisation energy, but also can increase solubility and electron mobility. So our designed compound 3 is expected to be a potential electron transport material in inverted PSCs. [ABSTRACT FROM AUTHOR]

In this paper, the rise and fall of lattice theories of the liquid state in middle of the twentieth century is discussed in the context of contemporary developments in statistical mechanics. [ABSTRACT FROM PUBLISHER]

Five bands of 15N14N18O nitrous oxide isotopologue were detected in the 4200–6500 cm−1 region with a Bruker IFS-125M Fourier transform spectrometer using a sample composed of NO (80% of 15N18O and 20% of 14N16O) and a trace amount of N2O isotopologues. The line positions of these bands were measured to the uncertainties of 0.001 cm−1. The spectroscopic constants were fitted using the measured line positions. The root mean squares of the residuals (RMS) of the fits (0.0005 cm−1 0.0027 cm−1) were close to the experimental uncertainties. Four bands, ν 1 + 2 ν 2 0 + ν 3 , 4 ν 1 , 2 ν 1 + 2 ν 2 0 + ν 3 , and ν 2 1 + 2 ν 3 − ν 2 1 , were observed for the first time. The line positions of the 2ν3 band were determined with a smaller uncertainty than in (A. W. Mantz, K. Narahari Rao, L.H. Jones, R.M. Potter. J. Mol. Spectrosc. 30, 513 (1969)). [ABSTRACT FROM AUTHOR]

Seeking environmentally friendly gas-insulated medium has become a research hotspot in recent years. At present, C3F7CN (Heptafluoro-iso-butyronitrile) is considered to be a potential SF6 environment-friendly alternative gas and some achievements have been made in the study of its insulation and decomposition characteristics, but there are few reports on the compatibility between its characteristic decomposition products and materials. The investigation of compatibility between gas-insulated medium and material is an important part of evaluating its comprehensive performance. In this paper, we investigated the interaction between C2F5CN, CF3CN, COF2 and CF4 with the aluminium widely used in electrical equipment. It was found that the interaction between C2F5CN, CF3CN and Al (1 1 1) surface is strong. There are obvious charge transfer and electron orbital overlap between the C atom, N atom in CN group and Al (1 1 1). The interaction between COF2, CF4 and Al (1 1 1) surface is weak and van der Waal’s forces play the major role. Relevant results reveal the characteristics of C3F7CN decomposition products and provide theoretical guidance for evaluating the material compatibility between C3F7CN decomposition products and aluminium. [ABSTRACT FROM AUTHOR]

Hierarchical self-assembly underpins much of the diversity of form and function seen in soft systems, yet the pathways by which they achieve their final form are not always straightforward - intermediate steps, kinetic effects and finite sizes of aggregates all influence the self-assembly pathways of these systems. In this paper, we use molecular dynamics simulations of binary mixtures of spheres and ellipsoidal discs to investigate the self-assembly of anisotropic aggregates with internal structures. Through this, the full aggregation pathways of spontaneously chiral, multi-bilayer and multi-layer assemblies have been tracked and characterised via a semi-qualitative analysis. This includes the unambiguous identification of first-, second- and third-generation hierarchical assemblies within a single simulation. Given the significant challenge of tracking full aggregation pathways in experimental systems, our findings strongly support the notion that molecular simulation has much to contribute to improving our understanding of hierarchical self-assembling systems. [ABSTRACT FROM AUTHOR]

The classical Oseen-Frank theory of liquid crystal elasticity is based on the experimentally verified fact that there are three independent modes of distortion, each with its associated elastic constant. On the other hand, the arguably more first-principles order parameter-based Landau-de Gennes theory only involves two independent elastic modes. The resulting ‘elastic constants problem’ has led to a considerable amount of vexation among theorists. In a series of papers at the turn of the century, Fukuda en Yokoyama suggested that the resolution of this problem could be found in the proper treatment of non-local effects in the ideal part of the free energy. They used an ingenious, but technically complex, technique based on a field-theoretic approach to semi-flexible polymers. Here we revisit their idea but now in the more accessible framework of density functional theory of rigid particles. Our work recovers their main results for rod-like particles, in that generically an ordered assembly of non-interacting rods has three independent elastic constants associated to it that all scale as the square of the length of the particles and obey the inequalities . We also consider the case of disc-like particles, and then find in line with expectations that . [ABSTRACT FROM AUTHOR]

The time reversal invariance of classical dynamics is reconsidered in this paper with specific focus on its consequences for time correlation functions and associated properties such as transport coefficients. We show that, under fairly common assumptions on the interparticle potential, an isolated Hamiltonian system obeys more than one time reversal symmetry and that this entails non trivial consequences. Under an isotropic and homogeneous potential, in particular, eight valid time reversal operations exist. The presence of external fields that reduce the symmetry of space decreases this number, but does not necessarily impair all time reversal symmetries. Thus, analytic predictions of symmetry properties of time correlation functions and, in some cases, even of their null value are still possible. The noteworthy case of a constant external magnetic field, usually assumed to destroy time reversal symmetry, is considered in some detail. We show that, in this case too, some of the new time reversal operations hold, and that this makes it possible to derive relevant properties of correlation functions without the uninteresting inversion of the direction of the magnetic field commonly enforced in the literature. [ABSTRACT FROM AUTHOR]

The so-called Gibbs’ paradox is a paradigmatic narrative illustrating the necessity to account for the N! ways of permuting N identical particles when summing over microstates. Yet, there exist some mixing scenarios for which the expected thermodynamic outcome depends on the viewpoint one chooses to justify this combinatorial term. After a brief summary on Gibbs’ paradox and what is the standard rationale used to justify its resolution, we will allow ourself to question from a historical standpoint whether the Gibbs’ paradox has actually anything to do with Gibbs’ work. In so doing, we also aim at shedding a new light with regards to some of the theoretical claims surrounding its resolution. We will then turn to the statistical thermodynamics of discrete and continuous mixtures and introduce the notion of composition entropy to characterise these systems. This will enable us to address, in a certain sense, a ‘curiosity” pointed out by Gibbs in a paper published in 1876. Finally, we will finish by proposing a connexion between the results we propose and a recent extension of the Landauer bound regarding the minimum amount of heat to be dissipated to reset one bit of memory. [ABSTRACT FROM AUTHOR]

A shear flow breaks the spherical symmetry of a flexible polymer, which has some interesting consequences for the electrophoresis of polyelectrolytes. In addition to introducing a chain-length dependence of the electrophoretic velocity, there is also the possibility of migration of the molecule perpendicular to the direction of coaxial gradients in pressure and electric potential. This has been shown to produce a rapid and highly localised concentration of DNA within a microfluidic capillary, with a number of potential applications to on-chip preparation and analysis of genomic DNA. In this paper, dedicated to Prof. Daan Frenkel, I will describe a calculation of the electrophoretic motion of a long polyelectrolyte under a coaxial flow and electric field. [ABSTRACT FROM AUTHOR]

The development of supersymmetric (SUSY) quantum mechanics has shown that some of the insights based on the algebraic properties of ladder operators related to the quantum mechanical harmonic oscillator (QMHO) carry over to the study of more general systems. At this level of generality, pairs of eigenfunctions of so-called partner Hamiltonians are transformed into each other, but the entire spectrum of any one of them cannot be deduced from this intertwining relationship in general - except in special cases. In this paper, we present a more general structure that provides all eigenvalues for a class of Hamiltonians that do not factor into a pair of operators satisfying canonical commutation relations. Instead of a pair of partner Hamiltonians, we consider two pairs that differ by an overall shift in their spectrum. This is called coupled supersymmetry. In that case, we also develop coherent states and present some uncertainty principles which generalise the Heisenberg uncertainty principle. Coupled SUSY is explicitly realised by an infinite family of differential operators which admit orthonormal bases of eigenfunctions of generalised harmonic oscillators. [ABSTRACT FROM AUTHOR]

The paper by Nold et al. [Phys. Fluids 26 (7), 072001 (2014)] examined density profiles and the micro-scale structure of an equilibrium three-phase (liquid-vapour-solid) contact line in the immediate vicinity of the wall using elements from the statistical mechanics of classical fluids, namely density-functional theory. The present research note, building on the above work, further contributes to our understanding of the nanoscale structure of a contact line by quantifying the strong dependence of the liquid-vapour density profile on the normal distance to the interface, when compared to the dependence on the vertical distance to the substrate. A recent study by Benet et al. [J. Phys. Chem. C 118 (38), 22079 (2014)] has shown that this could explain the emergence of a film-height-dependent surface tension close to the wall, with implications for the Frumkin-Derjaguin theory. [ABSTRACT FROM AUTHOR]

Lung cancer has received considerable attention in recent years due to its high mortality. The difficulty in awareness of such disease can be attributed to its strong insidiousness during the early stage. Therefore, the prognosis of lung cancer becomes significant so as to nip this disease in the bud. In this paper, the Rh-doped CNT-based biosensors were introduced to realise the diagnosis of lung cancer through detecting the exhaled gas of possible patients. The adsorption property and sensing mechanism of Rh-CNT towards two kinds of mainly typical gases of lung cancer, namely, C6H6 and C6H7N, were analysed based on density functional theory, aiming at evaluating the potential application of such material to be gas sensors. The results indicated that the Rh-CNT not only has good adsorption towards such two gases but also obvious conductivity increase when interacted with any of them, while presents insensitivity upon the common exhaled gas, CO2. We suggest the Rh-CNT be prepared as biosensors applied in the field of lung cancer pre-diagnosis that can be used in our daily life without pain and complex clinical examination. [ABSTRACT FROM AUTHOR]

Simulating energetic materials with complex microstructure is a grand challenge, where until recently, an inherent gap in computational capabilities had existed in modelling grain-scale effects at the microscale. We have enabled a critical capability in modelling the multiscale nature of the energy release and propagation mechanisms in advanced energetic materials by implementing, in the widely used LAMMPS molecular dynamics (MD) package, several novel coarse-graining techniques that also treat chemical reactivity. Our innovative algorithmic developments rooted within the dissipative particle dynamics framework, along with performance optimisations and application of acceleration technologies, have enabled extensions in both the length and time scales far beyond those ever realised by atomistic reactiveMDsimulations. In this paper,wedemonstrate these advances by modelling a shockwave propagating through a microstructured material and comparing performance with the state-of-the-art in atomistic reactive MD techniques. As a result of this work, unparalleled explorations in energetic materials research are now possible. [ABSTRACT FROM AUTHOR]

In this paper, we present a chain-of-sphere implementation of the external exchange term, the computational bottleneck of coupled-cluster calculations at the singles and doubles level. This implementation is compared to standard molecular orbital, atomic orbital and resolution of identity implementations of the same term within the ORCA package and turns out to be the most efficient one for larger molecules, with a better accuracy than the resolution-of-identity approximation. Furthermore, it becomes possible to perform a canonical CC calculation on a tetramer of nucleobases in 17 days, 20 hours. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive account on the recently developed dissipaton-equation-of-motion (DEOM) theory. This is a statistical quasi-particle theory for quantum dissipative dynamics. It accurately describes the influence of bulk environments, with a few number of quasi-particles, the dissipatons. The novel dissipaton algebra is then followed, which readily bridges the Schrödinger equation to the DEOM theory. As a fundamental theory of quantum mechanics in open systems, DEOM characterizes both the stationary and dynamic properties of system-and-bath interferences. It treats not only the quantum dissipative systems of primary interest, but also the hybrid environment dynamics that could be experimentally measurable. Examples are the linear or nonlinear Fano interferences and the Herzberg-Teller vibronic couplings in optical spectroscopies. This review covers the DEOM construction, the underlying dissipaton algebra and theorems, the physical meanings of dynamical variables, the possible identifications of dissipatons, and some recent advancements in efficient DEOM evaluations on various problems. The relations of the present theory to other nonperturbative methods are also critically presented. [ABSTRACT FROM AUTHOR]

The hierarchy of stochastic Schrödinger equation, previously developed under the unpolarised initial bath states, is extended in this paper for open quantum dynamics under polarised initial bath conditions. The method is proved to be a powerful tool in investigating quantum dynamics exposed to an ultraslow Ohmic bath, as in this case the hierarchical truncation level and the random sampling number can be kept at a relatively small extent. By systematically increasing the system-bath coupling strength, the symmetric Ohmic spin-boson dynamics is investigated at finite temperature, with a very small cut-off frequency. It is confirmed that the slow bath makes the system dynamics extremely sensitive to the initial bath conditions. The localisation tendency is stronger in the polarised initial bath conditions. Besides, the oscillatory coherent dynamics persists even when the system-bath coupling is very strong, in correspondence with what is found recently in the deep sub-Ohmic bath, where also the low-frequency modes dominate. [ABSTRACT FROM AUTHOR]

Spectroscopically accurate Potential Energy Surfaces (PESs) are fundamental for explaining and making predictions of the infrared and microwave spectra of van der Waals (vdW) complexes, and the model used for the potential energy function is critically important for providing accurate, robust and portable analytical PESs. The Morse/Long-Range (MLR) model has proved to be one of the most general, flexible and accurate one-dimensional (1D) model potentials, as it has physically meaningful parameters, is flexible, smooth and differentiable everywhere, to all orders and extrapolates sensibly at both long and short ranges. The Multi-Dimensional Morse/Long-Range (mdMLR) potential energy model described herein is based on that 1D MLR model, and has proved to be effective and accurate in the potentiology of various types of vdW complexes. In this paper, we review the current status of development of the mdMLR model and its application to vdW complexes. The future of the mdMLR model is also discussed. This review can serve as a tutorial for the construction of an mdMLR PES. [ABSTRACT FROM AUTHOR]

Substantial progress of the time-dependent density matrix renormalisation group (t-DMRG) method in the recent 15 years is reviewed in this paper. By integrating the time evolution with the sweep procedures in density matrix renormalisation group (DMRG), t-DMRG provides an efficient tool for real-time simulations of the quantum dynamics for one-dimensional (1D) or quasi-1D strongly correlated systems with a large number of degrees of freedom. In the illustrative applications, the t-DMRG approach is applied to investigate the nonadiabatic processes in realistic chemical systems, including exciton dissociation and triplet fission in polymers and molecular aggregates as well as internal conversion in pyrazine molecule. [ABSTRACT FROM AUTHOR]

The paper presents the results of ab initio modelling of the interaction of hydrogen atoms with ferrite/cementite interfaces in steels and thermodynamic assessment of the ability of interfaces to trap hydrogen atoms. Modelling was performed using the density functional theory with generalised gradient approximation (GGA’96), as implemented in WIEN2k package. An Isaichev-type orientation relationship between the two phases was accepted, with a habit plane (101)c∥ (112)α. The supercell contained 64 atoms (56 Fe and 8 C). The calculated formation energies of ferrite/cementite interface were 0.594 J/m2. The calculated trapping energy at cementite interstitial was 0.18 eV, and at the ferrite/cementite interface – 0.30 eV. Considering calculated zero-point energy, the trapping energies at cementite interstitial and ferrite/cementite interface become 0.26 eV and 0.39 eV, respectively. The values are close to other researchers’ data. These results were used to construct a thermodynamic description of ferrite/cementite interface-hydrogen interaction. Absorption calculations using the obtained trapping energy values showed that even thin lamellar ferrite/cementite mixture with an interlamellar spacing smaller than 0.1 μm has noticeable hydrogen trapping ability at a temperature below 400 K. [ABSTRACT FROM AUTHOR]

The goal of this work is to produce single species of polygons in two dimensions using the self-assembly of a simple patchy molecular model. A molecule is defined as a central soft repulsive Weeks Chandler and Anderson (WCA) atom that is decorated with two or four patches, which describe the two models studied in this work. Model I has two Lennard–Jones (LJ) patches inside of its central atom separated by an angle θ that intends to define the number of polygon sides. The attractive potential of these patches, interacting as pairs, is used to bond molecules together to form polygons. Model II, having two additional soft repulsive WCA patches, tangent on the outside, produces single polygon species configurations. An example of Model I with an angle $ \theta = 120^\circ $ θ = 120 ∘ , forming a mixture of polygons, is included. Model II produces single polygon species with 3-8 sides, depending on the angle θ between the attractive patches. Molecular dynamics simulations in the canonical ensemble are used to calculate thermodynamic properties such as internal energy, percentage of polygons, pressure and contour plots for the percentage of polygons following isochoric processes. Different starting configurations are used to verify the consistency of the equilibrium results. [ABSTRACT FROM AUTHOR]

Using molecular dynamics simulation, the surface tension is calculated and compared with experimental data to provide a microscopic interpretation of the synergistic effect on water surface tension reduction caused by a binary mixture composed of anionic and cationic surfactants. For the anionic and cationic surfactants, the sodium dodecyl sulphate (SDS) and the cetyl trimethylammonium bromide (CTAB) were used, respectively. Besides the electrostatic attraction between the anionic and cationic surfactants, resulting in a synergistic effect, other properties were analysed to study the reduction of the surface tension from a molecular level. For different SDS:CTAB composition of distinct properties of the pseudobinary mixture, such as the hydrogen bonds, order of the tails, and the arrangement of the surfactants at the interface were calculated. Those properties present different behaviours at the maximum and minimum values of the surface tension. The CTAB tails present a higher order than the SDS tails at all SDS:CTAB compositions however, the first ones show a maximum order at the minimum in the surface tension. The excess configurational energy was also calculated and shows a minimum value in the same composition as the minimum value of the surface tension. [ABSTRACT FROM AUTHOR]

The accuracy of four approximations proposed along time as equations of state for a homogeneous system of hard disks is compared against molecular dynamics results of $ 10^5 $ 10 5 disks in equilibrium [L. Mier-y-Terán, J. Munguía and J. Antonio Moreno-Razo, Mol. Phys. (2023). doi:]. Three of the equations studied here are Padé approximants. Only one of the approximations studied, based on the virial expansion of the compressibility factor of the homogeneous fluid, is considered to have sound physical grounds. Assuming that the total pressure predicted generates the positional part of the Helmholtz free energy, only, the four approximations, combined with the molecular dynamics simulation results referred above, allow identifying four linear regions, where different orientational processes can be associated with the well known steps of the melting transition. Results for a finite system are consistent with the KTHNY theory. In particular, under this assumption, the four approximations, with small quantitative differences, show the ordering effects present in the fluid at the low-density-end of the fluid-hexatic first-order phase transition. It is shown that the latter region continues to exist under the assumption proposed. In addition, a linear combination of the virial and compressibility coefficients is used to obtain a more accurate version of the Carnahan-Starling type approximation for the hard-disk system. [ABSTRACT FROM AUTHOR]

Thermodynamic and transport properties of particles interacting via the triangular-well potential in the range of $ 1.4 \leq \lambda \leq ~2.6 $ 1.4 ≤ λ ≤ 2.6 have been studied using perturbation theory and Molecular Dynamics simulations. We present thermodynamic properties such as vapour-liquid coexistence, vapour pressures, and density for different values of the attractive range potential. Good agreement is observed between the theoretical approach and computer simulations in a wide range of densities, temperatures, and pressures. Additionally, we show Molecular Dynamic simulation results of transport properties such as the self-diffusion coefficient as a function of both density and temperature. Finally, thermodynamic and transport properties of real fluids like oxygen, methane, hydrogen sulfide, and fluoromethane have been predicted using both approaches. Results of vapour-liquid coexistence, vapour pressures, and critical points were in excellent agreement with experimental data. The coupling of perturbation theory, Molecular Dynamics simulations, and the triangular-well pair potential offers a versatile and efficient method to explore various real fluid systems, which would include associating fluids, complex molecular liquids, and colloidal systems. This approach can advance our understanding of these systems using a simple approach and to contribute the development of more accurate and predictive models. [ABSTRACT FROM AUTHOR]

The glass transition is a process in which a non-periodic solid is obtained by fast cooling a melt. In this work, an analysis is made of the energy landscape kinetic equations that allow to describe such phenomena. In particular, it is shown that the glass transition occurs at the boundary layer of the energy landscape kinetic master equations, as solutions always have steep gradients and are very sensitive to the initial conditions. Moreover, it is discussed that the evolution operator is given by a path integral where the cooling rate plays a role akin to the Planck constant in a quantum mechanical problem. As an example, the kinetic equation properties of a two-level fully connected energy landscape system, capable of exhibiting both a glass and a thermodynamic phase transition, both of which are analytically solvable, are analysed in detail. [ABSTRACT FROM AUTHOR]

Humans affect the biosphere by producing entropy as living beings –as explained by Schröedinger [What is Life? The physical aspect of the living cell (Cambridge University Press, New York, 1992)] – but mostly as a consequence of our ever increasing economic interventions. However, humans also create new forms and arrangements of matter. Is it possible that they carry less entropy than equivalent object subject to natural forces? Art and tech works tell us something, thus carry information. The connection between probability and information was introduced by Shannon 75 years ago [Bell Syst. Tech. J. 27, 379–423 (1948)]. In this work we calculate the probability that a stone tool could have been constructed by random, natural causes. We do so by considering the earliest tools created by our hominin ancestors, the stone tools of the Paleolithic. By analysing a sample of tools, we show that they are highly unlikely constructs by random means, and that therefore carry a great deal of information, as generations of archaeologists and anthropologists have eloquently exhibited. Further, we quantify this information, and following Shannon, we ascribe an entropy to the stone tools. We thus find that the stone tool carries less entropy than a stone hit by dispersed blows. This work presents a first simplified approach to these important issues. [ABSTRACT FROM AUTHOR]

In this work, we have calculated self-diffusion and shear viscosity, two of the most important transport properties, of the spherical square-well (SW) fluid interacting with potential range $ \lambda = 1.5 \, \sigma $ λ = 1.5 σ. To this end, we have used a combination of molecular dynamics simulation and the continuous version of the square-well (CSW) intermolecular potential recently proposed by Zerón et al. [Mol. Phys. 116, 3355 (2018)]. In addition to that, we have also determined a number of equilibrium properties, including internal energy, compressibility factor, radial distribution function and coordination number. All properties are evaluated in a wide range of temperatures and densities, including subcritical and supercritical thermodynamic conditions. Results obtained in this work show an excellent agreement with available data reported in the literature and demonstrate that the CSW intermolecular potential can be used in molecular dynamics simulations to emulate SW transport properties with confidence. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations of simple Lennard Jones fluids confined in slit-like pores were studied for the gas–liquid transition using weak and very attractive walls. Several fluid–wall potential strengths were simulated and pressure transitions were obtained at different temperatures. In the case of weak fluid–wall interaction typical results were found, the gas–liquid transition pressure increases with the temperature. When the fluid–wall becomes more attractive, the transition pressure increases significantly but decreases with the temperature. For a very attractive wall, i.e. the fluid–wall interaction is very strong, the transition pressure decreases with the temperature given a negative slope of the coexistence line in the P-T phase diagram. Analysis of the systems in terms of the energy shows that for weak walls the difference in the potential and kinetic energies drops at the transition pressure and the enthalpy of adsorption is negative whereas for strong walls the difference in energies increases at the transition and the adsorption enthalpy has positive values. [ABSTRACT FROM AUTHOR]

For molecular dynamics simulations of hard particles, we define dynamic neighbours as the distinct particles that collide with a given reference one during a specific time interval. This definition allows us to determine the distribution of the number of dynamic neighbours, its average, and its standard deviation. We will show that regardless of the time window used to identify dynamic neighbours, their distribution is correlated with diffusion coefficients, structure, and configurational entropy. Thus, it is likely that the distribution of the number of dynamic neighbours may be employed as another tool to gain insights into the dynamic behaviour of hard-core systems. We tested this approach on 2D and 3D systems consisting of monodisperse and binary mixtures of hard disks and spheres. Results show that implementing dynamic neighbours to define order parameters can sharpen the signals where transitions take place. [ABSTRACT FROM AUTHOR]

Based on an equilibrium thermodynamic scheme, this work studies the separation of the Helmholtz free energy of a hard-disk system into its positional and orientational contributions. For the positional part, an accurate two dimensional version of the Carnahan-Starling equation of state is proposed, while a simple ansatz of the one particle partition function for the orientational part is proposed. The latter expression, which contains information about the probability of the norm of the six-fold orientational order parameter, is obtained through molecular dynamics simulations. Perhaps due to finite size effects, the ordering of the fluid is not a sudden phenomenon: the fluid-hexatic phase transition is preceded by a linear increase in the orientational contribution to the pressure of the fluid. A similar result is obtained for the hexatic-solid phase transition. Thus, the hexatic first-order phase transition is located between two linear ordering processes, consistent with the KTHNY theory. The proposed separation also predicts the existence of first order fluid-hexatic phase transition by using two procedures: the first, based on a purely bimodal probability density function, produces a pressure with a van del Waals-like first-order phase transition, while the second, considering density fluctuations, results in a flattened pressure phase transition. [ABSTRACT FROM AUTHOR]

A Monte Carlo simulation study on the charge distribution and structure of the electric double layer (EDL) that forms between two planar interfaces is presented, using a model electrolyte of monovalent hard-sphere ions and confining walls composed of two discrete and sign-alternating charge distributions. Symmetric and asymmetric plate-plate orientations, along with uncharged walls, are considered. Results are presented for effective wall-ion correlation functions and local integrated charge in the subvolumes defined by the charge domains on the plates. We report that, in the presence of multifaceted charged surfaces, the ions between the walls exhibit complex and rich behavior, with the formation of an EDL next to the charged domains of the interface, and having density profiles of counterions and coions that are established as function of the nature and configuration of the charged strips. These profiles present a structural frustration that renders the subvolumes with a net charge, in contrast to the null net charge from profiles next to a uniformly charged surface. Finally, with proper scaling, the integrated charge follows closely a master curve for each wall-wall configuration. Such phenomenology is visible in the regime of low and high surface charge. [ABSTRACT FROM AUTHOR]

In this work, the binding mean spherical approximation (BiMSA) theory is used to describe osmotic and activities coefficients for electrolytes solutions up to high temperatures. Four salts are analysed: NaCl, LiCl, $ {\rm MgCl}_2 $ MgCl 2 and $ {\rm CaCl}_2 $ CaCl 2 , in the temperature range of 25 $ ^{\circ } $ ∘ C to 300 $ ^{\circ } $ ∘ C and molalities from 0.05 to 6 molal. A good representation of experimental data is obtained for all salts and temperatures considered by introducing temperature-dependent cation size and permittivity in a suitable way. The proportion of ion pairs (that are formed at sufficiently high temperature in these solutions) for each salt is predicted from the theory, showing a pronounced increase for temperatures above 100 $ ^{\circ } $ ∘ C. A good agreement is found between the values of optimised and experimental association constants given in the literature. [ABSTRACT FROM AUTHOR]

A coarser model for the Gay-Berne mesogen is developed using the interaction potential from the Approximate Non-Conformal (ANC) theory. The ANC potential contains both repulsive and attractive contributions. We modify intermolecular attractions by conditioning them with a Hess-Su orientation-dependent term. This imparts an anisotropic contribution to the energy of the system. The softness parameter s of the ANC potential is probed to qualitatively identify a threshold capable of sustaining a nematic phase. We construct phase diagrams for each value of s from molecular dynamics simulations and characterise bulk samples to outline phase regions. We find that a softness parameter $ s \sim 0.6 $ s ∼ 0.6 or higher supports the emergence of a nematic phase. The stability of the nematic region is enhanced as $ s\to 1 $ s → 1 , corresponding to the conventional Lennard-Jones interaction. The stability of the nematic phase for nearly-spherical mesogens with increasing s leads to a gradual loss in spherical symmetry despite no imposed shape anisotropy. Thus, the energy anisotropy becomes more pronounced and is capable of prompting the emergence of the nematic phase in this model. [ABSTRACT FROM AUTHOR]

The second virial coefficient, the Boyle temperature and the equation of state of van Hove fluids with a relatively short ranged attractive parabolic-well of downward concavity are considered. The analytic second virial coefficient for this fluid is obtained explicitly and it is used to compute the Boyle temperature of the fluid as a function of the range of the potential. Further, an equation of state is derived using the second-order thermodynamic perturbation theory of Barker and Henderson in the macroscopic compressibility approximation, with the hard-sphere fluid being the reference fluid. For this latter we profit from the fully analytical expression of the radial distribution function, consistent with the Carnahan-Starling equation state, derived within the so-called rational function approximation method up to a range twice the size of the hard-core diameter. The results for the reduced pressure of the fluid as a function of the packing fraction and two values of the range of the potential well at different temperatures are compared with Monte Carlo simulation data. Estimates of the values of the critical temperature are also provided. [ABSTRACT FROM AUTHOR]

Models of fractal growth commonly consider particles diffusing in a medium and that stick irreversibly to the forming aggregate when making contact for the first time. As shown by the well-known diffusion limited aggregation (DLA) model and its generalisations, the fractal dimension is sensitive to the nature of the stochastic motion of the particles. Here, we study the structures formed by finite-lived Brownian particles, i.e. particles constrained to find the aggregate within a prescribed time, and which are removed otherwise. This motion can be modelled by diffusion with stochastic resetting, a class of processes which has been widely studied in recent years. In the short lifetime limit, a very small fraction of the particles manage to reach the aggregate. Hence, growth is controlled by atypical Brownian trajectories, that move nearly in straight line according to a large deviation principle. In d dimensions, the resulting fractal dimension of the aggregate decreases from the DLA value and tends to 1, instead of increasing to d as expected from ballistic aggregation. In the zero lifetime limit one recovers the non-trivial model of 'aggregation by the tips' proposed long ago by R. Jullien [J. Phys. A: Math. Gen. 19, 2129 (1986)]. [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of benzyl 4-([1,1'-biphenyl]-4-yl)-2-methyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate are described. Single crystal X-ray diffraction of title molecule was used to investigate the crystal structure. The most stable optimised structure was identified using the B3LYP/6-31 + G(d) method. IR, 1H-NMR and elemental analysis of the title compound were performed. Besides, frontier molecular orbitals, molecular electrostatic potential, and thermodynamic properties were investigated by theoretically. In order to explore the nonlinear optical properties were performed theoretically. Hirshfeld analysis was also performed to determine the interactions of the molecule. [ABSTRACT FROM AUTHOR]

In order to understand the enhancement mechanism of the interaction between functionalised carbon nanotubes and polymer matrix, and to investigate the effects of different functionalised carbon nanotubes on the properties of composites at the microscopic level, the models of pure polyurethane (PUR), carbon nanotubes/polyurethane (CNTs/PUR), hydroxyl-functionalised carbon nanotubes/polyurethane (CNTOH/PUR), and carboxyl-functionalised carbon nanotubes/polyurethane (CNTCOOH/PUR) systems were constructed, and molecular dynamics methods were used to simulate the effects of different functionalised carbon nanotubes on the mechanical properties of polyurethane composite systems. The effects of different functionalised carbon nanotubes on the properties of PUR composite systems were compared by analysing the properties of PUR and its composite systems in terms of free volume fraction (FFV), radial distribution function (RDF), binding energy, and density distribution of PUR around different functionalised carbon nanotubes. The effects of intermolecular interactions on the properties of the composite systems were elucidated at the microscopic level. The final simulation results show that the CNTCOOH/PUR composite system with added carboxylated CNTs has the highest tensile yield strength, compressive properties and modulus; the smallest free volume fraction; the strongest bonding energy between CNTCOOH and PUR matrix, the largest density distribution of PUR matrix around CNTCOOH, and the best interfacial interaction. [ABSTRACT FROM AUTHOR]

Computational experiments were carried out to find a tiny sensor that can detect the Lomustine (LT) drug. The experiments studied how the sensor interacts with regular and aluminum-doped boron nitride sheets (BN-yne and Al-BN). The calculations reveal that the LT medication mainly attaches to the B atom in the BN-yne molecule through its NO group, and the binding energy is −5.2 kcal/mol. Using the LT drug only changes the electronic features of the original BN-yne sheet a little. Replacing a B atom with an Al atom in the –B = N– connection significantly enhances the reactivity and responsiveness of the BN-yne sheet to the LT drug. The electrical conductivity increases because the energy gap of Al-BN decreases from 4.81 to 3.08 eV. Moreover, its work function (Φ) has been significantly reduced from 3.51 to 2.55 eV, which causes an increment in the field emission electron current. Eventually, what is expected is a short recovery time of 3.9 sec for the desorption of LT from the Al-BN surface. As the results suggest, Al-BN can work as perfectly as an electronic sensor to acquire the LT drug. [ABSTRACT FROM AUTHOR]

$ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n (n=1-5) clusters have been computationally studied using DFT and TDDFT with B3LYP functional under hybrid GGA approximation and LANL2DZ basis set. The doping effect of various elements like Ba, Y and Hf on the structural, electronic and non-linear optical (NLO) properties of $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters has been studied for finding their optoelectronic applications. Different optimised geometries of $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n and Ba, Y and Hf doped $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters have been obtained. HOMO-LUMO gap $ (\Delta \mathcal {E}) $ (Δ E) and chemical hardness (τ) of $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters decreases significantly with doping of Ba, Y and Hf atoms making these clusters very reactive. Refractive index and the absorption in UV–VIS region of electromagnetic spectra of Ba, Y and Hf doped $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters increases as compared to $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters making these clusters suitable to be used as additives in the manufacturing of various types of glasses. Also, dielectric constant (ϵ) of Ba, Y and Hf doped $ ({\rm La}_2 {\rm O}_3)_{\rm n} $ (La 2 O 3) n clusters increases finding their applications to be used in the oxide layer of MOSFETs. [ABSTRACT FROM AUTHOR]

Zintl (group IV elements) clusters with a special number of valence electrons often exhibit extraordinary structures and chemical bonding patterns, and the stability of them is rationalised by the Wade-Mingos rule. However, this rule is still limited for some Zintl clusters. Here, we find that the potential energy surface of PtSn5 has a single deep funnel, which leads down to the octahedron of the global minimum. The AIMD simulations demonstrate that the octahedral PtSn5 still has a good thermal stability at 1000 K. The molecular orbitals and AdNDP analyses reveal that the 20 valence electrons from five Sn atoms of the PtSn5 fill superatomic shells resulting in an electronic configuration of 1S21P61D102S2, and the electronic structure of the Pt atom is d10, well following the magic number of the Jellium model. The result is further confirmed by the density of states and the localised orbital locator. After the CO molecule is adsorbed on the PtSn5, it prefers to be located at the Pt atom. Due to the charge-transfer effect, the C–O bond length and stretching frequency appear to change significantly. Our work opens up the study on the Jellium model for Zintl clusters. [ABSTRACT FROM AUTHOR]

This article delves into the domain of low bandgap perovskite solar cells, driven by the quest for enhanced device performance and expanded access to various solar energy spectra. The study systematically explores the materials, device design, and optimization strategies pertinent to low bandgap perovskite solar cells. The initial section focuses on the current status of low bandgap perovskite materials, scrutinizing approaches to enhance bandgap, stability, and charge transport. Novel materials such as mixed-halide perovskites, double perovskites, and perovskite quantum dots are examined to improve efficiency and broaden the spectral utilization. The investigation culminates in a comprehensive exploration of diverse device topologies aimed at enhancing the performance of low bandgap perovskite solar cells. This encompasses discussions on electron and hole transport materials, interfacial engineering techniques, various device designs, tandem configurations, and their respective merits and limitations. Additionally, the research scrutinizes methodologies to enhance the performance of low-bandgap perovskite solar cells, with a specific focus on light management, charge extraction, and mitigating recombination losses. The incorporation of passivation layers and interfacial modifications is discussed as a strategy for bolstering device stability and mitigating deterioration through interface engineering. [ABSTRACT FROM AUTHOR]

The present study aims to quantify the electron-induced inelastic and elastic processes for molecules of industrial relevance, furfural and p-benzoquinone. We have computed inelastic cross-sections (Qinel), elastic cross-sections (Qel) and total cross-sections (QT) through spherical complex optical potential (SCOP) formalism, from ionisation energy (IE) to 5000 eV. The continuum and discrete contributions of the Qinel have been calculated in terms of ionisation (Qion) and excitation (∑Qexc) cross-sections, respectively, by employing the complex scattering potential-ionisation contribution (CSP-iC) method. A novel 2-parameter semi-empirical method (2p-SEM), a useful approach applicable for the large molecules 55 < Z < 95 for calculating QT, has been proposed and validated. Computed results are compared with previous experimental and theoretical data. We have also estimated the dielectric constant (ε) using various methods and correlations with molecular ionisation for these applied molecules. [ABSTRACT FROM AUTHOR]

The present work evaluates pristine and amino acid-functionalised C4B32 borospherenes for drug delivery purposes based on density functional theory (DFT). C atoms were doped on $ \textrm{B}_{36}^{ - 4} $ B 36 − 4 clusters to develop C4B32 borospherenes, and C4B32 clusters in pristine and alanine-modified forms have shown significant drug delivery performance. This study sought to evaluate the interactions of both pristine and alanine-modified C4B32 with isoniazid drug (IS) based on DFT calculations. The amino acid modification expectedly enabled biodrug carrier functionality and enhanced the adsorption of IS onto C4B32. The UV-Visible (UV-Vis) analysis revealed a redshift upon the adsorption of IS. It was concluded that alanine-modified C4B32 clusters could serve as a promising drug carrier. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are popular in the market due to their ability to charge and many applications in life. In these rechargeable batteries, Lithium ions move from the positive electrode to the negative electrode during charging and in the opposite direction during discharge. In the present research, the effect of external electric field amplitude (EEFA) with different ratios of 0.1, 0.2, 0.3, and 0.5 V/Å on the Li-ion-C-anode nanobattery was investigated by molecular dynamics (MD), and the effect of EEFA (0.1–0.5 V/Å) on the Mean squared displacement (MSD) was checked. It is concluded that for the Li-Li pair, the NN distance presents a slight tendency to decrease. Moreover, with the increase in the intensity of the EEFA, the number of mobile lithium ions increased from 60 to 183. Numerically, with increasing EEFA from 0.1–0.2, 0.3, and 0.5 V/Å, the MSD of lithium increased from 38.28–59.22, 89.91, and 113.04 nm2. This behaviour indicated that the lithiation of the carbon is occurring and that the lithium ions can diffuse through the carbon structure by breaking C–C bonds and forming a LiC alloy wall. [ABSTRACT FROM AUTHOR]