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

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

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

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

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

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

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]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The machine learning approach applied to materials discovery is a popular research direction. Knowledge of quantum chemistry explains that the structure of a material determines its properties. Graph neural networks (GNNs) provide a unique way of predicting the macroscopic properties of molecules and crystals rather than by solving the computationally expensive Schrödinger equation. Graph neural networks can abundantly transform the structural information of materials into corresponding features, and many models based on graph neural networks have been applied to predict material properties. We developed a new model (DYCGNN) containing a node update module for our designed edge-graph attention network composition. Through the application of the edge-gatv2 module, this module can effectively learn the complex relationship between nodes and neighbouring nodes in the crystal. Based on the calculated weight coefficients of each neighbouring node, the representation of the node is updated more effectively. In addition, we fuse the position information of the nodes into the node eigenvectors to complement the spatial information of the crystal and enrich the complete representation of the crystal. As we investigate the DYCGNN model, we find that our approach can outperform the predictions of previous models and provide insights into material crystallization. [ABSTRACT FROM AUTHOR]

Studies have shown that alkali metal ultrafine water mist additives, such as NaCl and KCl, are highly effective in inhibiting explosion and combustion. In order to further study the heterogeneous catalytic inhibition of NaCl and KCl, the 100 most stable surfaces of NaCl and KCl were selected as the research objects. Three typical free radicals (H, O, OH) were selected as surface adsorbents with different coverages, and the most stable adsorption sites and configurations were located. The NEB method was used to calculate the minimum energy paths of H and O recombination on two surfaces. The molecular dynamics of two surface combustion radicals were simulated by the AIMD method. The results indicated that NaCl and KCl have strong adsorption capacity for the O free radical, while the two surfaces have weaker adsorption capacity for the H free radical; NaCl and KCl, two catalytic active substances, which can eliminate H radicals through the continuous adsorption of H free radical to generate H2, and H radical is inactivated. The catalytic fire-extinguishing effect by eliminating O free radical is weak. Molecular dynamics calculations on the two surfaces revealed that Cl atoms precipitate differently under the adsorption of various radicals. [ABSTRACT FROM AUTHOR]

In this study, we utilised the GGA+U method via the WIEN2k software to investigate the structural, magnetic, and optoelectronic responses of two distinct surfaces, (111) and (110), to Ni adsorption on CdO at the Cd site. The analysis revealed that Ni/CdO (111) demonstrates properties akin to a semimetal or a zero-gap semiconductor across both spin orientations, while Ni/CdO (110) exhibits a metallic nature under similar conditions. These phenomena are predominantly ascribed to the orbital contributions from Ni-d, Cd-d, and O-p for the Ni/CdO (111), and Ni-d, Cd-d, and O-s for the Ni/CdO (110), respectively. A notable blue shift in the optical absorption spectra was observed for both materials. Utilising the Dielectric function, we calculated the dispersion of energy bands along with essential optical properties, including the absorption coefficient, energy loss function, and reflectivity, refractive index, and extinction coefficient. Magnetisation values for Ni/CdO (110) and Ni/CdO (111) were recorded at (−0.11794) µB and (2.17926) µB, respectively, influenced by the absorption spectrum's blue shift. Additionally, transport properties were evaluated using the BoltzTraP software over a temperature range of 0 to 800 K. Our findings suggest that Ni/CdO (110) and Ni/CdO (111) are significant for applications in spintronics and energy devices. [ABSTRACT FROM AUTHOR]

MPAA was synthesised and evaluated using spectroscopic methods and quantum chemical computations in the proposed investigation. Extensive quantum chemical computations were employed to analyse FT-IR, FT-Raman and NMR spectra of molecule morpholinium adipate (MPAA). The results of a single crystal X-ray diffraction (SCXRD) experiment were compared with estimated structural characteristics. In conjunction with the scaled force constants, a comprehensive vibrational assignment is provided for the 96 anticipated vibration modes of MPAA. Charge transport inside the molecule is exposed by the band gap energy of 5.959 eV, which is the consequence of the predicted Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) values of −6.991 and −1.031 eV, respectively. The inter- and intramolecular H-bonding contacts in the molecule were studied using natural bond orbital analysis to learn more about the biological active site. The eventual charge transfer inside the molecule is supported by frontier molecular orbital analysis and natural bond orbital analysis. The anti-bonding of H15–O24 atoms and the lone pair N14 had the greatest stabilising energy at 16.52 kcal/mol. Using Hirshfeld surface analysis methods, intermolecular connections and crystal packing of MPAA are investigated. The fukui and electrostatic potential plot analyses can provide information about the molecule's electrophilic and nucleophilic locations. Antimicrobial tests have been performed to see how well the chemical worked against various bacterial and fungal strains. Docking of 8OEO (Aspergillus Niger), 7C2O (Candida parapsilosis), 2O6I (Enterococcus faecalis) and 1DZO (Pseudomonas aeruginosa) proteins has been done, and lowest binding energy −4.57 kcal/mol has been achieved for 7C2O protein. [ABSTRACT FROM AUTHOR]

To predict the biological effects of chemical compounds based on mathematical and statistical relationships, quantitative structure–activity relationship (QSAR) approach is used. Based on the molecular characteristics of diverse substances, Quantitative Structure–Property Relationship (QSPR) techniques estimate the physiochemical attributes whereas Quantitative Structure Toxicity Relationship (QSTR) is used as a link between the molecular structure of species and its toxicity. These ligand-based computational screening methods offer a cost-effective replacement for laboratory-based screening procedures. Different QSTR models are established to understand the biological activities related to toxicity. Density Functional Theory (DFT) and ab-initio techniques are used to examine external acute toxicity using Quantum Chemical (QC) descriptors and the electron correlation contribution. Conceptual Density Functional Theory (CDFT) based global and local descriptors have wide applications in analysing various physical and chemical characteristics of chemical species. The descriptors like chemical hardness, electronegativity, electrophilicity index, HOMO–LUMO energy, and enthalpy are found reliable to predict the model in terms of available experimental data. Various mathematical models are established through Multi Linear Regression (MLR) analysis which links the calculated descriptors with their biological activities. In this review, the applications of CDFT-based descriptors, are described in detail for QSAR / QSPR/ QSTR studies. [ABSTRACT FROM AUTHOR]

This study aims to cast light on the nature of hydrogen bonds and their cooperativity that exists in alcohol-water ( $ \textrm{ROH}{({{\textrm{H}_2}\textrm{O}})_\textrm{n}} $ ROH ( H 2 O ) n ) ( $ \textrm{R} = - \textrm{C}{\textrm{H}_3}\textrm{ }({ - \textrm{Me}}),\textrm{ } - \textrm{C}{\textrm{H}_2}\textrm{C}{\textrm{H}_3}\textrm{ }({ - \textrm{Et}}) $ R = − C H 3 (− Me) , − C H 2 C H 3 (− Et)) (n = 1–10) clusters using atoms in molecules (AIM) theory and symmetry-adapted perturbation theory (SAPT). The investigation of optimum structures suggests that alcohol ( $ \textrm{ROH} $ ROH ) forms two hydrogen bonds, one primary hydrogen bond $ ({\textrm{O} - \textrm{H} \cdot \cdot \cdot \textrm{O}}) $ (O − H ⋅ ⋅ ⋅ O) , and one secondary hydrogen bond $ ({\textrm{C} - \textrm{H} \cdot \cdot \cdot \textrm{O}}) $ (C − H ⋅ ⋅ ⋅ O) Two types of hydrogen bonds are addressed in these studies, where alcohol works as the hydrogen bond donor $ ({\textrm{ROH} \cdot \cdot \cdot \textrm{O}{\textrm{H}_2}}) $ (ROH ⋅ ⋅ ⋅ O H 2 ) and hydrogen bond acceptor $ ({\textrm{RHO} \cdot \cdot \cdot \textrm{HOH}}) $ (RHO ⋅ ⋅ ⋅ HOH). The AIM results reveal that $ \textrm{RHO} \cdot \cdot \cdot \textrm{HOH} $ RHO ⋅ ⋅ ⋅ HOH and $ \textrm{ROH} \cdot \cdot \cdot \textrm{O}{\textrm{H}_2} $ ROH ⋅ ⋅ ⋅ O H 2 hydrogen bonds are partially covalent. The SAPT study demonstrates that in all the clusters studied herein, the electrostatic interaction between alcohol and water is the main attractive force, and its contribution may be two times larger than the separate corresponding contributions from the dispersion and the induction terms. The electron density (ρ) at the bond critical point (BCP) is a suitable parameter to assess the strength of the interaction. The current study shows the strength and nature of $ \textrm{ROH} \cdot \cdot \cdot \textrm{O}{\textrm{H}_2} $ ROH ⋅ ⋅ ⋅ O H 2 and $ \textrm{RHO} \cdot \cdot \cdot \textrm{HOH} $ RHO ⋅ ⋅ ⋅ HOH hydrogen bond, and cooperative effect in ( $ \textrm{ROH}{({{\textrm{H}_2}\textrm{O}})_\textrm{n}} $ ROH ( H 2 O ) n ) ( $ \textrm{R} = - \textrm{C}{\textrm{H}_3}\textrm{ }({ - \textrm{Me}}),\textrm{ } - \textrm{C}{\textrm{H}_2}\textrm{C}{\textrm{H}_3}\textrm{ }({ - \textrm{Et}}) $ R = − C H 3 (− Me) , − C H 2 C H 3 (− Et).) (n = 1–10). [ABSTRACT FROM AUTHOR]

As is known, novel organic molecules with amazing characteristics of excited-state intramolecular proton transfer (ESIPT) have become a hot and fascinating topic. Herein, our main attention is to investigate the dynamic behaviour of 2-benzoxazol-2-yl-6-triethylsilanylethynyl-phenol (BYTP), an intriguing derivative derived from 2-(2-hydroxyphenyl)benzoxazole (HBO). Dependent on examining four different aprotic solvents with varying levels of polarity, we can confirm without a doubt that solvent polarity has a big impact on the way hydrogen bonding interactions, redistribution as well as reorganisation of charge, and associated ESIPT phenomena occur when light is involved. After carefully comparing and accurately measuring reaction barriers in different solvent environments, our groundbreaking findings strongly suggest that highly polar solvents are good at helping the ESIPT reaction for BYTP fluorophore happen. We really hope that this study can give us some insight into how BYTP behaves when it's excited and influenced by solvent polarity, while also opens up possibilities for future research and applications involving other new HBO derivatives. [ABSTRACT FROM AUTHOR]

As widely acknowledged, the realm of novel organic molecules boasting extraordinary attributes pertaining to excited-state intramolecular proton transfer (ESIPT) has emerged as a captivating subject matter. In this context, our primary focus lies in delving into the excited-state behaviour exhibited by 2-benzoxazol-2-yl-4-triethylsilanylethynyl-phenol (BY4TP), an alluring derivative derived from 2-(2-hydroxyphenyl)benzoxazole (HBO). Relying on the examination of four distinct aprotic solvents with varying degrees of polarities, we can unequivocally affirm that solvent polarity exerts a profound influence on the intricate interplay of hydrogen bonding interactions, charge redistribution and reorganisation, as well as associated ESIPT phenomena by light. Through meticulous comparison and precise measurement of reaction barriers across diverse solvent environments, our groundbreaking findings indicate that lowly polar solvents serve as efficacious facilitators for promoting the occurrence of the ESIPT reaction in BY4TP fluorophore. By considering atomic-electronegativity-regulated hydrogen bonding effects and excited state behaviours for BY4TP-S and BY4TP-Se, we also present low atomic electronegativity with Se substation promotes ESIPT reaction. We ardently anticipate that this study will provide invaluable insights into the behaviour exhibited by BY4TP upon excitation and under the influence of solvent polarity and atomic electronegativity, while simultaneously paving new avenues for future research endeavours and applications encompassing novel HBO derivatives. [ABSTRACT FROM AUTHOR]

Nucleation and growth of methane clathrate hydrates is an exceptional playground to study crystallisation of multi-component, host-guest crystallites when one of the species forming the crystal, the guest, has a higher concentration in the solid than in the liquid phase. This adds problems related to the transport of the low concentration species, here methane. A key aspect in the modelling of clathrates is the water model employed in the simulation. In previous articles, we compared an all-atom force model, TIP4P/Ewald, with a coarse grain one, which is highly appreciated for its computational efficiency. Here, we perform a complementary analysis considering three all-atoms water models: TIP4P/Ewald, TIP4P/ice and TIP5P. A key difference between these models is that the former predicts a much lower freezing temperature. Intuitively, one expects that to lower freezing temperatures of water correspond to lower water/methane–methane gas–clathrate coexistence ones, which determines the degree of supercooling and the degree of supersaturation. Hence, in the simulation conditions, 250 K (500 atm, and fixed methane molar fraction), one expects computational samples made of TIP4P-ice and TIP5P, with a similar freezing temperature ( $ T_f \sim 273 $ T f ∼ 273 K), to be more supersaturated with respect to the case of TIP4P-Ew ( $ T_f \sim 245 $ T f ∼ 245 K), and crystallisation to be faster. Surprisingly, we find that while the nucleation rate is consistent with this prediction, growth rate with TIP4P-ice and TIP5P is much slower than with TIP4P-Ew. The latter was attributed to the slower reorientation of water molecules in strong supercooled conditions, resulting in a lower growth rate. This suggests that the freezing temperature is not a suitable parameter to evaluate the adequacy of a water model. [ABSTRACT FROM AUTHOR]

We investigate the equilibrium properties of responsive hard-sphere fluids, where the particle size is a coarse-grained property that fluctuates within an internal free-energy landscape, responding to changes in concentration or the application of external fields. For this purpose, we employ a generalised density functional theory for responsive colloids based on the fundamental measure theory for polydisperse hard-sphere mixtures. We find that increasing particle softness yields a substantial reduction in mean particle size, volume fraction and pressure. We also examine the density profiles and size segregation of responsive hard-sphere fluids subjected to three representative external potentials: a planar hard wall, gravitational and Archimedes buoyant fields. We observe that increasing stiffness or particle concentration enhances density oscillations, converging to the behaviour of a monodisperse fluid. In a gravitational field, size segregation occurs, with smaller particles accumulating at the bottom due to sedimentation. This effect is more pronounced when the Archimedes force is included, causing larger colloids to accumulate at the top, leading to density oscillations in this region that intensify with particle softness, an effect not observed in monodisperse systems. Finally, we demonstrate that responsiveness leads to distinct behaviour compared to conventional polydisperse non-responsive fluids, in which particle compression is not allowed. [ABSTRACT FROM AUTHOR]

Non-equilibrium random fluctuations of a non-thermal nature are a defining feature of active matter. In this work, we study the collective excitations of active systems at high density, focusing on a one-dimensional chain of elastically coupled inertial particles, where activity is modeled by an Ornstein–Uhlenbeck process. The excitation spectrum reveals two types of fluctuations: thermally excited phonons, analogous to those in passive crystals, and entropons, which are associated with entropy production due to active forces. These fluctuations exhibit distinct properties: only entropons generate spatial velocity correlations and violate the standard fluctuation-response relation. We derive exact expressions for equal-time velocity and displacement correlations, as well as for the structure factor, identifying the contributions from both phonons and entropons. Finally, we explore the dynamical properties of these excitations through steady-state two-time correlations, such as the intermediate scattering function and mean-square displacement. Both phonon and entropon fluctuations are characterized by a long-wavelength overdamped regime and a short-wavelength underdamped regime. In the large persistence case, entropons decay more slowly than phonons, and activity generally suppresses the oscillations typical of the underdamped regime. [ABSTRACT FROM AUTHOR]

Ions significantly alter the water's structure, impacting properties such as the temperature of maximum density and the freezing point. We study structural changes in water upon adding sulfate anions, specifically $ {\rm Na}_2{\rm SO}_4 $ Na 2 SO 4 , $ {\rm K}_2{\rm SO}_4 $ K 2 SO 4 , $ {\rm Li}_2{\rm SO}_4 $ Li 2 SO 4 , and $ {\rm Mg}{\rm SO}_4 $ Mg SO 4 , using computer simulations. We employ the TIP4P/2005 water and the Madrid-2019 force field. By simulating solutions at various concentrations (0.64, 1.30, 1.90, and 3 mol kg $ ^{-1} $ − 1 ) and two temperatures (300 and 240 K), we explore how these electrolytes disrupt water's structure and how they modify the interplay between Low Density Water and High Density Water. Increased salt concentration perturbed water's radial distribution functions (RDFs), particularly up to 240 K. $ {\rm Na}_2{\rm SO}_4 $ Na 2 SO 4 significantly disrupted water structure, reducing RDF peak heights and indicating decreased tetrahedrality, while $ {\rm Mg}{\rm SO}_4 $ Mg SO 4 increased structural order. $ {\rm K}_2{\rm SO}_4 $ K 2 SO 4 displayed anomalous behaviour, minimally affecting water at 1.90 mol kg $ ^{-1} $ − 1 and ambient temperature but causing more ordered structures at 240 K. Orientational order parameter $ q_t $ q t analysis supported these findings. Hydrogen bond network analysis showed notable perturbations at lower temperatures. Diffusion coefficients generally decreased with concentration, with $ {\rm K}_2{\rm SO}_4 $ K 2 SO 4 exhibiting increase at 240 K. These results highlight the complex interactions between sulfate ions and water, enhancing our understanding of electrolyte solutions. [ABSTRACT FROM AUTHOR]

This study evaluates the capabilities of two new ion force fields (Tanaka [Yagasaki et al. JCTC 2020] and Madrid-2019 [Zerón et al. JCP 2019]) in conjunction with the TIP4P/2005 model for water in reproducing the NaCl–water phase diagram using molecular dynamics direct coexistence simulations. The performance of those force-fields is critically compared with the phase diagram recently reported for the Joung Cheatham-TIP4P/2005 force-field [Bianco et al. JCP 2022]. Excellent agreement between the three force-fields and experiments is found for the ice-solution line due to the dominance of the water model in the location of this line. For the NaCl-solution line, the Tanaka and the Madrid-2019 models accurately predict solubility at ambient temperature, but they underestimate somewhat the experimental line as temperature increases. The JC model underestimates NaCl solubility both at ambient and at high temperatures. All models underestimate the stability of the NaCl·2H $ _2 $ 2 O solid, which remains metastable with respect to NaCl. Equilibration of the NaCl·2H $ _2 $ 2 O-solution system is challenging at low temperatures due to the slow diffusion of concentrated NaCl solutions. The phase diagrams obtained serve as a foundation for studying crystal nucleation, and solid-solution interfaces, and provide very valuable information for the development of imporved NaCl–H $ _2 $ 2 O force-fields. [ABSTRACT FROM AUTHOR]

A widely accepted phenomenological rule states that solids with free surfaces cannot be overheated. In this work we discuss this statement critically under the light of the statistical thermodynamics of interfacial roughening transitions. Our results show that the basal face of ice as described by the TIP4P/Ice model can remain mechanically stable for more than one hundred nanoseconds when overheated by 1 K, and for several hundreds of nanoseconds at smaller overheating despite the presence of a significant quasi-liquid layer at the surface. Such time scales, which are often of little experimental significance, can become a concern for the determination of melting points by computer simulations using the direct coexistence method. In the light of this observation, we reinterpret computer simulations of ice premelting and show that current results for the TIP4P/Ice model all imply a scenario of incomplete surface melting. Using a thermodynamic integration path, we reassess our own estimates for the Laplace pressure difference between water and vapour. These calculations are used to measure the disjoining pressure of premelting liquid films and allow us to confirm a minimum of the interfacial free energy at finite premelting thickness of about one nanometer. [ABSTRACT FROM AUTHOR]

Cyclic alcohols are commonly found in natural and synthetic products and are involved in many biological processes. An ability to model their thermodynamic properties is of interest in food, flavouring, and pharmaceutical manufacturing, particularly for mixtures for which available experimental data are limited. Good examples are mixtures including menthol, a naturally occurring cyclic alcohol widely used in the food and pharmaceutical industries, well-known for its cooling-sensation properties and its role in the discovery of the TRPM8 receptor. Here, we extend the SAFT-γ Mie group-contribution method to model cyclic alcohols, by introducing a new cCHOH group (c for cyclic) composed of two identical Mie segments. Three association sites (two electronic sites of type e and one hydrogen site of type H) are also included to mediate hydrogen bonding. New parameters that characterise the group interactions (one new like interaction and 26 new unlike interactions) are developed and are employed to determine the thermophysical properties (vapour pressure, saturation density, vaporisation enthalpy, and second-order thermodynamic derivative properties) of pure cyclic alcohols, and mixture properties (vapour–liquid equilibria, liquid–liquid equilibria, solid–liquid equilibria, density, and excess enthalpy) of cyclic alcohols in several solvents. The quality of the model is evaluated by comparing predictive calculations with experimental data of 76 systems: six pure fluids and 70 binary mixtures, selected from a large range of solvent families: cyclic, linear, and branched alkanes, 1-alcohols, 2-alcohols, 2-ketones, esters, aromatic compounds, water, and carbon dioxide. Very good overall agreement is found, including for the prediction of solid–liquid solubility, which confirms the transferability of the new group parameters. Together with previously developed parameters, these open the way for the prediction of the thermodynamic properties of further complex mixtures. [ABSTRACT FROM AUTHOR]

Averaged local bond order parameters based on spherical harmonics, also known as Lechner and Dellago order parameters, are routinely used to determine crystal structures in molecular simulations. Among different options, the combination of the $ \bar {q}_{4} $ q ¯ 4 and $ \bar {q}_{6} $ q ¯ 6 parameters is one of the best choices in the literature since distinguishes between solid- and liquid-like particles and between different crystallographic phases, including cubic and hexagonal phases. Recently, Algaba et al. [J. Colloid Interface Sci. 623, 354, (2022)] have used the Lechner and Dellago order parameters to distinguish hydrate- and liquid-like water molecules in the context of determining the carbon dioxide hydrate-water interfacial free energy. According to the results, the preferred combination previously mentioned is not the best option to differentiate between hydrate- and liquid-like water molecules. In this work, we revisit and extend the use of these parameters to deal with systems in which clathrate hydrates phases coexist with liquid phases of water. We consider carbon dioxide, methane, tetrahydrofuran, nitrogen, and hydrogen hydrates that exhibit sI and sII crystallographic structures. We find that the $ \bar {q}_{3} $ q ¯ 3 – $ \bar {q}_{12} $ q ¯ 12 combination is the best option possible between a large number of possible different pairs to distinguish between hydrate- and liquid-like water molecules in all cases. [ABSTRACT FROM AUTHOR]

Supercritical water has attracted much attention from both fundamental and technological perspectives, based largely on its ability to solvate other molecules. Predicting and controlling this requires a deeper understanding of water's polarisation behaviour. Using the computationally efficient Self-Consistent Electrostatic Embedding method, we were able to calculate the water dipole moment over an unprecedented range of thermodynamic conditions, covering gas, liquid and supercritical states, with large simulation systems and a high-level quantum mechanical method. We find a discontinuous change in the dipole moment along subcritical isotherms, corresponding to the sharp transition between the vapour and liquid states, with the latter exhibiting induced dipole moments between 0.5 and 0.9 D, depending on the temperature. In contrast, the dipole moment changes continuously from gas-like to liquid-like behaviour in the supercritical regime, allowing the degree of polarisation to be controlled through manipulating temperature and pressure. The dipole moment was found to be linearly related to the average number of hydrogen-bonded neighbours of water, emphasising the key role of local interactions to the polarisation process. Mean-field approaches based on a dielectric continuum representation of the solvent are unable to predict this behaviour due to the neglect of local interactions. [ABSTRACT FROM AUTHOR]

We have investigated the effect of adding polar rodlike nanoparticles (NPs) to a liquid crystal using Monte Carlo simulations. The mesogens (Ms) are represented with Gay–Berne elongated ellipsoids endowed with a central axial electric dipole. A NP is instead modelled by a overall rod-like set of rigidly assembled Lennard–Jones spherical beads (Orlandi et al. Phys. Chem. Chem. Phys. 18, 2428–2441 (2016). doi:10.1039/C5CP05754J) that are either non-polar or endowed with a central axial dipole of different strengths. We consider two cases: one of strong NP-M affinity and weak NP-NP interactions (case 1) and the opposite one of weak NP-M affinity and strong NP-NP interactions (case 2). We find that for case 1 adding polar NPs slightly lowers the nematic-isotropic transition temperature $ T_{NI} $ T NI which instead, for case 2, is essentially unaffected. Having strongly polar, instead of non-polar NPs reduces the $ T_{NI} $ T NI difference with the pristine one, while significantly increasing the dielectric anisotropy in the nematic phase, which could be useful in applications. [ABSTRACT FROM AUTHOR]