We study fluid-fluid equilibrium in the simplest model of ionic solutions where the solvent is explicitly included, i.e., a binary mixture consisting of a restricted primitive model (RPM) and neutral hard-spheres (RPM-HS mixture). First, using the collective variable method we find free energy, pressure and partial chemical potentials in the random phase approximation (RPA) for a rather general model that takes into consideration solvent-solvent and solvent-ion interactions beyond the hard core. In the special case of a RPM-HS mixture, we consider two regularizations of the Coulomb potential inside the hard core, i.e., the Weeks-Chandler-Andersen (WCA) regularization leading to the WCA approximation and the optimized regularization giving the optimized RPA (ORPA) or the mean spherical approximation (MSA). Furthermore, we calculate the phase coexistence using the associative mean spherical approximation (AMSA). In general, the three approximations produce qualitatively similar phase diagrams of the RPM-HS mixture, i.e., a fluid-fluid coexistence envelope with an upper critical solution point, a shift of the coexistence region towards higher total number densities and higher solvent concentrations with increasing pressure, and a small increase of the critical temperature with an increase of pressure. As for a pure RPM, the AMSA leads to the best agreement with the available simulation data when the association constant proposed by Olaussen and Stell is used. We also discuss the peculiarities of the phase diagrams in the WCA approximation.
Conventional lithium-ion batteries, and many next-generation technologies, rely on organic electrolytes with multiple solvents to achieve the desired physicochemical and interfacial properties. The complex interplay between these properties can often be elucidated via the coordination environment of the cation. We develop a theory for the coordination shell of cations in non-aqueous solvent mixtures that can be applied with high fidelity, up to super-concentrated electrolytes. Our theory can naturally explain simulation and experimental values of cation solvation in ''classical'' non-aqueous e…
The decay of correlations in ionic fluids is a classical problem in soft matter physics that underpins applications ranging from controlling colloidal self-assembly to batteries and supercapacitors. The conventional wisdom, based on analyzing a solvent-free electrolyte model, suggests that all correlation functions between species decay with a common decay length in the asymptotic far field limit. Nonetheless, a solvent is present in many electrolyte systems. We show using an analytical theory and molecular dynamics simulations that multiple decay lengths can coexist in the asymptotic limit as…
In this contribution, a new POM-based ionic liquid, namely (P6,6,6,14)4[W10O32], was fully characterized. Its viscosity and its very low dielectric constant make this hybrid ionic liquid suitable to be used as solvent for organic transformations. As proof of concept, this unique ionic liquid combining solvant and catalyst properties was tested for catalytic oxidation of various alcohols and alkenes in presence of H2O2
The structure and interactions in electrolytes at high concentration have implications from energy storage to biomolecular interactions. However many experimental observations are yet to be explained in these mixtures, which are far beyond the regime of validity of mean field models. Here, we study the structural forces in a mixture of ionic liquid and solvent that is miscible in all proportions at room temperature. Using the surface force balance to measure the force between macroscopic smooth surfaces across the liquid mixtures, we uncover an abrupt increase in the wavelength above a thresho…
In this paper, we study the electroosmotic transport in a nanofluidic channel by using a mean-field theory accounting for non-uniform size effect and solvent polarization effect. We witness that in the presence of the given zeta potential, an enhancement of ion size invariably lowers the electroosmotic velocity, thereby increasing the magnitude of electrostatic potential, irrespective of considering solvent polarization. It is also proved that solvent polarization allows both the magnitude of electrostatic potential and the electroosmotic velocities to decrease. In addition, we find that incre…
We have performed a thorough examination of the reorientational relaxation dynamics and the ionic charge transport of three typical deep eutectic solvents, ethaline, glyceline and reline by broadband dielectric spectroscopy. Our experiments cover a broad temperature range from the low-viscosity liquid down to the deeply supercooled state, allowing to investigate the significant influence of glassy freezing on the ionic charge transport in these systems. In addition, we provide evidence for a close coupling of the ionic conductivity in these materials to reorientational dipolar motions which sh…
We introduced a new concept for fabricating solvent stimulus polymer actuators with unprecedented sensitivity and accuracy. This was accomplished by integrating porous architectures and electrostatic complexation gradients in a poly(ionic liquid) membrane that bears ionic liquid species for solvent sorption. In contact with 1.5 mol% of acetone molecules in water, the actuator membrane (1 mm x 20 mm x 30 um) bent into a closed loop. While the interaction between solvents and the polymer drives the actuation, the continuous gradient in complexation degree combined with the porous architecture op…
Ionic microgel particles are intriguing systems in which the properties of thermo-responsive polymeric colloids are enriched by the presence of charged groups. In order to rationalize their properties and predict the behaviour of microgel suspensions, it is necessary to develop a coarse-graining strategy that starts from the accurate modelling of single particles. Here, we provide a numerical advancement of a recently-introduced model for charged co-polymerized microgels by improving the treatment of ionic groups in the polymer network. We investigate the thermoresponsive properties of the par…
We revisit the role of the local solvent structure on the activity coefficient of electrolytes with a general non-local dielectric function approach. We treat the concentrated electrolyte as a dielectric medium and suggest an interpolated formula for the dielectric response. The pure water limit is calibrated based on MD simulations and experimental data. Solving our model around a central ion, we find strong over-screening and oscillations in the potential, which are absent in the standard "primitive model" predictions. We obtain mathematically tractable closed-form expressions for the activi…
The dielectric constant of ionic solutions is known to reduce with increasing ionic concentrations. However, the origin of this effect has not been thoroughly explored. In this paper we study two such possible sources: long-range Coulombic correlations and solvent excluded volume. Correlations originate from fluctuations of the electrostatic potential beyond the mean-field Poisson-Boltzmann theory, evaluated by employing a field-theoretical loop expansion of the free energy. The solvent excluded-volume, on the other hand, stems from the finite ion size, accounted for via a lattice-gas model. W…
Effects of charge-density fluctuations on a phase behavior of the restricted primitive model (RPM) are studied within a field-theoretic formalism. We focus on a $λ$-line of continuous transitions between charge-ordered and charge-disordered phases that is observed in several mean-field (MF) theories, but is absent in simulation results. In our study the RPM is reduced to a $ϕ^6$ theory, and a fluctuation contribution to a grand thermodynamic potential is obtained by generalizing the Brazovskii approach. We find that in a presence of fluctuations the $λ$-line disappears. Instead, a fluctuation-…
We study a fluid-fluid phase transition of the explicit solvent model represented as a mixture of the restricted primitive model (RPM) of ionic fluid and neutral hard spherocylinders (HSC). To this end, we combine two theoretical approaches, i.e., the scale particle theory (SPT) and the associative mean spherical approximation (AMSA). Whereas the SPT is sufficient to provide a rather good description of a reference system taking into account hard-core interactions, the AMSA is known to be efficient in treating the Coulomb interactions between the ions. Alternatively, we also use the mean spher…
There is a growing interest in the properties of ionic liquids (ILs) and IL-solvent mixtures at metallic interfaces, particularly due to their applications in energy storage. The main focus so far has been on electrical double layers with ILs far from phase transitions. However, the systems in the vicinity of their phase transformations are known to exhibit some remarkable features, such as wetting transitions and capillary condensation. Herein, we develop a mean-field model suitable for the IL-solvent mixtures close to demixing, and combine it with the Carnahan-Starling (CS) and lattice-gas e…
We have studied the ionic conductivity and the dipolar reorientational dynamics of aqueous solutions of a prototypical deep eutectic solvent (DES), ethaline, by using dielectric spectroscopy on a broad range of frequency (MHz-Hz) and for temperatures ranging from 128 to 283 K. The fraction of water in the DES was varied systematically to cover different regimes, starting from pure DES and its water-in-DES mixtures to the diluted electrolyte solutions. Depending on these parameters, different physical states were examined, including low viscosity liquid, supercooled viscous liquid, amorphous so…
We investigate the electric double layer formed between charged walls of a slit-like pore and a solvent primitive model (SPM) for electrolyte solution. The recently developed version of the weighted density functional approach for electrostatic interparticle interaction is applied to the study of the density profiles, adsorption and selectivity of adsorption of ions and solvent species. Our principal focus, however, is in the dependence of differential capacitance on the applied voltage, on the electrode and on the pore width. We discuss the properties of the model with respect to the behavior…
The molecular dynamics (MD) simulation study of solvation structure and free energetics in 1-ethyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium hexafluorophosphate using a probe solute in the preceding article [Y. Shim, M. Y. Choi and H. J. Kim, cond-mat/0501305] is extended to investigate dynamic properties of these liquids. Solvent fluctuation dynamics near equilibrium are studied via MD and associated time-depedent friction is analyzed via the generalized Langevin equation. Nonequilibrium solvent relaxation following an instantaneous change in the solute charge distribution …
Lithium-salt-based deep eutectic solvents, where the only cation is Li+, are promising candidates as electrolytes in electrochemical energy-storage devices like batteries. We have performed broadband dielectric spectroscopy on three such systems, covering a broad temperature and dynamic range that extends from the low-viscosity liquid around room temperature down to the glassy state approaching the glass-transition temperature. We detect a relaxational process that can be ascribed to dipolar reorientational dynamics and exhibits the clear signatures of glassy freezing. We find that the tempera…
Ionic liquids (ILs), also known as room-temperature molten salts, are composed of pure ions with melting points usually below 100 degrees centigrade. Because of their low volatility and vast amounts of species, ILs can serve as "green solvents" and "designer solvents" to meet the requirements of various applications by fine tuning their molecular structures. A good understanding of the phase behaviors of ILs is certainly fundamentally important in terms of their wide applications. This review intends to summarize the major conclusions so far drawn on phase behaviors of ILs by computational, th…
Ionic microgel particles in a good solvent swell to an equilibrium size determined by a balance of electrostatic and elastic forces. When crowded, ionic microgels deswell owing to a redistribution of microions inside and outside the particles. The concentration-dependent deswelling affects the interactions between the microgels, and consequently the suspension properties. We present a comprehensive theoretical study of crowding effects on thermodynamic, structural, and dynamic properties of weakly cross-linked ionic microgels in a good solvent. The microgels are modeled as microion- and solven…
We investigate the liquid-vapor interface of the restricted primitive model for an ionic fluid using a density functional approach. The applied theory includes the electrostatic contribution to the free energy functional arising from the bulk energy equation of state and the mean spherical approximation for a restricted primitive model, as well as the associative contribution, due to the formation of pairs of ions. We compare the density profiles and the values of the surface tension with previous theoretical approaches.
We study the effect of solvent granularity on the effective force between two charged colloidal particles by computer simulations of the primitive model of strongly asymmetric electrolytes with an explicitly added hard sphere solvent. Apart from molecular oscillating forces for nearly touching colloids which arise from solvent and counterion layering, the counterions are attracted towards the colloidal surfaces by solvent depletion providing a simple statistical description of hydration. This, in turn, has an important influence on the effective forces for larger distances which are considerab…
We propose several versions of primitive models of room temperature ionic liquids (RTILs) and develop a mean spherical approximation (MSA)-type theory for their description. RTIL is modeled as a two-component mixture of hard-sphere anions and flexible linear chain cations, represented by tangentially bonded hard spheres with the charge located on one of the terminal beads. The theoretical description of the model is carried out using the solution of the appropriately modified associative MSA (AMSA). Our solution reduces to solving one nonlinear algebraic equation for the Blum's screening param…
It has been recently shown that a viscosity gradient could drive electrical current through a negatively charged nanochannel (Wiener and Stein, arXiv: 1807.09106). To understand the physics underlying this phenomenon, we employed the Maxwell-Stefan equation to obtain a relation between the flux of solvent species and the driving forces. Our 1D model, which was derived for both ideal and non-ideal solvents, shows that the ionic current depends on the ideality of the solvent, though both scenarios demonstrated good agreement with experimental data. We employed the model to understand the impact …
The restricted primitive model with nonadditive hard-sphere diameters is shown to have interesting and peculiar clustering properties. We report accurate calculations of the cluster concentrations. Implementing efficient and ad hoc Monte Carlo algorithms we determine the effect of nonadditivity on both the clustering and the gas-liquid binodal. For negative nonadditivity, tending to the extreme case of completely overlapping unlike ions, the prevailing clusters are made of an even number of particles having zero total charge. For positive nonadditivity, the frustrated tendency to segregation o…
The effects of ionic valency and size asymmetry on counterion adsorption
School of Physics and Astronomy, Tel Aviv University（特拉维夫大学物理与天文学学院）；Center for Physics and Chemistry of Living Systems, Tel Aviv University（特拉维夫大学生物系统物理与化学中心）；School of Chemistry, Tel Aviv University（特拉维夫大学化学学院）；School of Physical Sciences and Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学与柯夫利理论科学研究所）；Wenzhou Institute, University of Chinese Academy of Sciences（中国科学院大学温州研究院）；CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所软物质物理重点实验室）
The phase behaviour and dynamics of molecular ionic liquids are studied using primitive models and extensive computer simulations. The models account for size disparity between cation and anion, charge location on the cation, and cation-shape anisotropy, which are all prominent features of important materials such as room-temperature ionic liquids. The vapour-liquid phase diagrams are determined using high-precision Monte Carlo simulations, setting the scene for in-depth studies of ion dynamics in the liquid state. Molecular dynamics simulations are used to explore the structure, single-partic…
This work presents a rigorous statistical mechanical theory of solvation free energies, specifically useful for describing the long-range nature of ions in an electrolyte solution. The theory avoids common issues with field theories by writing the excess chemical potential directly as a maximum-entropy variational problem in the space of solvent 1-particle density functions. The theory was developed to provide a simple physical picture of the relationship between the solution's spatial dielectric function, ion screening, and the chemical potential. The key idea is to view the direct correlatio…
Using a continuum description, we account for fluctuations in the ionic solvent surrounding a Gaussian, charged chain and derive an effective short-ranged potential between the charges on the chain. This potential is repulsive at short separations and attractive at longer distances. The chemical potential can be derived from this potential. When the chemical potential is positive, it leads to a melt-like state. For a vanishingly low concentration of segments, this state exhibits scaling behavior for long chains. The Flory exponent characterizing the radius of gyration for long chains is calcul…
We report an accurate Monte Carlo calculation of the phase diagram and clustering properties of the restricted primitive model with non-additive hard-sphere diameters. At high density the positively non-additive fluid shows more clustering than the additive model and the negatively non-additive fluid shows less clustering than the additive model, at low density the reverse scenario appears. A negative nonadditivity tends to favor the formation of neutrally charged clusters starting from the dipole. A positive nonadditivity favors the pairing of like ions at high density. The critical point of …
Solvents comprise two thirds of all industrial emissions. Traditional organic solvents easily reach the atmosphere as they have high vapor pressure and are linked to a host of negative environmental effects including climate change, urban air-quality and human illness. Room temperature ionic liquids (RTIL), on the other hand, have low vapor pressure and are not flammable or explosive, thereby resulting in fewer environmental burdens and health hazards. However, their life cycle environmental impacts as well as freshwater ecotoxicity implications are poorly understood. RTILs are molten salts th…
Although the volume transition of the polyelectrolyte gel has been studied for decades, little research on the effects of size of the mobile ions has been conducted. In the present paper, Tanaka classical theory of polyelectrolyte gel is extended to the cases of mobile ions of finite volume. In the salt free limit, the theoretical results show that the discontinuous volume transition of the polyelectrolyte gel will become a continuous one with an increase of the counter-ionic size. An increase in salt concentration can also make the polyelectrolyte gel in poor solvent collapse. Poorer solvent …
A coarse-grained description of the restricted primitive model is considered in terms of the local charge- and number-density fields. Exact reduction to a one-field theory is derived, and exact expressions for the number-density correlation functions in terms of higher-order correlation functions for the charge-density are given. It is shown that in continuum space the singularity of the charge-density correlation function associated with short-wavelength charge-ordering disappears when charge-density fluctuations are included by following the Brazovskii approach. The related singularity of th…
A theory of a confined two dimensional electrolyte is presented. The positive and negative ions, interacting by a $1/r$ potential, are constrained to move on an interface separating two solvents with dielectric constants $ε_1$ and $ε_2$. It is shown that the Debye-Hückel type of theory predicts that the this 2d Coulomb fluid should undergo a phase separation into a coexisting liquid (high density) and gas (low density) phases. We argue, however, that the formation of polymer-like chains of alternating positive and negative ions can prevent this phase transition from taking place.
We performed rheological measurements of the typical deep eutectic solvents (DESs) glyceline, ethaline, and reline in a very broad temperature and dynamic range, extending from the low-viscosity to the high-viscosity supercooled-liquid regime. We find that the mechanical compliance spectra can be well described by the random free-energy barrier hopping model, while the dielectric spectra on the same materials involve significant contributions arising from reorientational dynamics. The temperature-dependent viscosity and structural relaxation time, revealing non-Arrhenius behavior typical for g…
The increasing number of experimental observations on highly concentrated electrolytes and ionic liquids show qualitative features that are distinct from dilute or moderately concentrated electrolytes, such as self-assembly, multiple-time relaxation, and under-screening, which all impact the emergence of fluid/solid interfaces, and transport in these systems. Since these phenomena are not captured by existing mean field models of electrolytes, there is a paramount need for a continuum framework for highly concentrated electrolytes and ionic liquids. In this work, we present a self-consistent s…
We study discrete solvent effects on the interaction of two parallel charged surfaces in ionic aqueous solution. These effects are taken into account by adding a bilinear non-local term to the free energy of Poisson-Boltzmann theory. We study numerically the density profile of ions between the two plates, and the resulting inter-plate pressure. At large plate separations the two plates are decoupled and the ion distribution can be characterized by an effective Poisson-Boltzmann charge that is smaller than the nominal charge. The pressure is thus reduced relative to Poisson-Boltzmann prediction…
We report results of molecular dynamics simulations characterizing the solvation and interaction of small apolar particles such as methane and Xenon in imidazolium-based ionic liquids (ILs). The simulations are able to reproduce semi-quantitatively the anomalous temperature dependence of the solubility of apolar particles in the infinite dilution regime. We observe that the ``solvophobic solvation'' of small apolar particles in ILs is governed by compensating entropic and enthalpic contributions, very much like the hydrophobic hydration of small apolar particles in liquid water. In addition, o…
A mesoscopic theory for the primitive model of ionic systems is developed for arbitrary size, $λ=σ_+/σ_-$, and charge, $Z=e_+/|e_-|$, asymmetry. Our theory is an extension of the theory we developed earlier for the restricted primitive model. The case of extreme asymmetries $λ\to\infty$ and $Z \to\infty$ is studied in some detail in a mean-field approximation. The phase diagram and correlation functions are obtained in the asymptotic regime $λ\to\infty$ and $Z \to\infty$, and for infinite dilution of the larger ions (volume fraction $n_p\sim 1/Z$ or less). We find a coexistence between a very …
Porous and flexible actuating materials are important in the development of smart systems. We report here a facile method to prepare scalable, flexible actuating porous membranes based on a poly(ionic liquid)-modified tissue paper. The targeted membrane property profile was based on a synergy of a gradient porous structure of poly(ionic liquid) network and the flexibility of tissue paper. The gradient porous structure was built up through ammonia-triggered electrostatic complexation of a poly(ionic liquid) with poly(acrylic acid) (PAA) that were previously impregnated inside the tissue paper. …
The influence of dilute impurities on the structure of a fluid solvent is investigated theoretically. General arguments, which do not rely on particular models, are used to derive an extension of the Ornstein-Zernike form for the solvent structure factor at small scattering vectors. It is shown that dilute impurities can influence the solvent structure only if they are composed of ions with significantly different sizes. Non-ionic impurities or ions of similar size are shown to not alter the solvent structure qualitatively. This picture is compatible with available experimental data. The deriv…
We investigate the modification of gas phase ion polarizabilities upon solvation in polar solvents and ionic liquids. To this aim, we develop a classical electrostatic theory of charged liquids composed of solvent molecules modeled as finite size dipoles, and embedding polarizable ions that consist of Drude oscillators. In qualitative agreement with ab-initio calculations of polar solvents and ionic liquids, the hydration energy of a polarizable ion in both type of dielectric liquid is shown to favor the expansion of its electronic cloud. Namely, the ion carrying no dipole moment in the gas ph…
We review our recent studies on selective solvation effects in phase separation in polar binary mixtures with a small amount of solutes. Such hydrophilic or hydrophobic particles are preferentially attracted to one of the solvent components. We discuss the role of antagonistic salt composed of hydrophilic and hydrophobic ions, which undergo microphase separation at water-oil interfaces leading to mesophases. We then discuss phase separation induced by a strong selective solvent above a critical solute density np, which occurs far from the solvent coexistence curve. We also give theories of ion…
Recent Monte Carlo simulations of the critical point of the restricted primitive model for ionic solutions are reported. Only the continuum version of the model is considered. A finite size scaling analysis based in the Bruce-Wilding procedure gives critical exponents in agreement with those of the three-dimensional Ising universality class. An anomaly in the scaling of the specific heat with system size is pointed out.
Ionic Liquids (ILs) are organic molten salts characterized by the total absence of solvent. They show remarkable properties: low vapor pressure, high ionic conductivity, high chemical, thermal and electrochemical stability. These electrolytes meet therefore key criteria for the development of safe energy storage systems. Due to a competition between electrostatic and van der Walls interactions, ILs show an uncommon property for neat bulk liquids: they self-organize in transient nanometric domains. In ILs-based electrochemical devices, this fluctuating nano-segregation acts as energy barriers t…
Ton Duc Thang University（东德克萨斯大学）；Duy Tan University（越南岘港大学）；Petroleum University of Technology (PUT)（石油技术大学）；Amirkabir University of Technology（阿米尔卡比尔理工大学）；Obuda University（欧布达大学）；Oxford Brookes University（牛津布鲁克斯大学）；Bauhaus Universität-Weimar（魏玛包豪斯大学）；J. Selye University（塞耶大学）
Industry uses various solvents in the processes of refrigeration and ventilation. Among them, the Ionic liquids (ILs) as the relatively new solvents, are known for their proven eco-friendly characteristics. In this research, a comprehensive literature review was carried out to deliver an insight into the ILs and the prediction models used for estimating the ammonia solubility in ILs. Furthermore, a number of advanced machine learning methods, i.e. multilayer perceptron (MLP) and a combination of particle swarm optimization (PSO) and adaptive neuro-fuzzy inference system (ANFIS) models are used…
Porous polymer membranes via electrostatic complexation triggered by neutralization are fabricated for the first time from a water-soluble poly(ionic liquid) (PIL). The porous structure is formed as a consequence of simultaneous phase separation of the PIL and ionic complexation, which occurred in a basic solution of a non-solvent for the PIL. These membranes have a stimuli-responsive porosity, with open and closed pores in isopropanol and in water, respectively. This property is quantitatively demonstrated in filtration experiments, where water is passing much slower through the membranes tha…
Underscreening is a collective term for charge correlations in electrolytes decaying slower than the Debye length. Anomalous underscreening refers to phenomenology that cannot be attributed alone to steric interactions. Experiments with concentrated electrolytes and ionic fluids report anomalous underscreening, which so far has not been observed in simulation. We present Molecular Dynamics simulation results exhibiting anomalous underscreening that can be connected to cluster formation. A theory that accounts for ion pairing confirms the trend. Our results challenge the classic understanding o…
In this work, we perform a comparative study of the size dependence of diffusion of charged and neutral solutes in water. The neutral solute in water shows a nonmonotonicity in the size dependence of diffusion. This is usually connected to the well known Levitation effect where it is found that when solute diffuses through the transient solvent cages then for attractive solute-solvent interaction and for a particular size of the solute there is a force balance which leads to the maximum in diffusion. Similar maximum in diffusion of charged solutes has also been observed and connected to Levita…
The work reports transport and structure properties of the three pyridinium-based ionic liquids (RTILs) - N-butylpyridinium hexafluorophosphate [BPY][PF6], N-butylpyridinium trifluorosulfonate [BPY][TF] and N-butylpyridinium bis(trifluoromethanesulfonyl)imide [BPY][TFSI] - in their mixtures with acetone (ACET). The ionic conductivity maximum occurs at 10 mol% RTIL, irrespective of the anion. The absolute ionic conductivity value of [BPY][TF] is higher than those of other RTILs. This is explained by a weaker cation-anion binding than that in [BPY][PF6] and smaller anion size than that of [BPY][…
We discuss the first three well known moment charge-charge sum-rules for a general ionic liquid. For the special symmetric case of the Restricted Primitive Model, Das et al. [Phys. Rev. Lett. 107, 215701 (2011)] has recently discovered, through Monte Carlo simulations, that the Stillinger-Lovett or second-moment sum-rule fails at criticality. We critically discuss a possible explanation for this unexpected behavior. On the other hand the fourth-moment sum-rule turns out to be able to account for the results of the simulations at criticality.
We use Monte Carlo simulations to examine the simplest model of an ionic liquid, called the restricted primitive model, at a metal surface. We find that at moderately low temperatures the capacitance of the metal/ionic liquid interface is so large that the effective thickness of the electrostatic double-layer is up to 3 times smaller than the ion radius. To interpret these results we suggest an approach which is based on the interaction between discrete ions and their image charges in the metal surface and which therefore goes beyond the mean-field approximation. When a voltage is applied acro…
Like-charge attraction, driven by ionic correlations, challenges our understanding of electrostatics both in soft and hard matter. For two charged planar surfaces confining counterions and water, we prove that even at relatively low correlation strength, the relevant physics is the ground-state one, oblivious of fluctuations. Based on this, we derive a simple and accurate interaction pressure, that fulfills known exact requirements and can be used as an effective potential. We test this equation against implicit-solvent Monte Carlo simulations and against explicit-solvent simulations of cement…
