The nonlocal density functional theory (NLDFT) of confined fluids is tested against Monte Carlo simulations by using the example Lennard-Jones (LJ) fluid sorption in slit-shaped and cylindrical nanopores ranging from 0.3 to 10 nm width. fluid-fluid solid-fluid parameters LJ potentials were chosen represent several experimentally important adsorption systems: nitrogen carbon dioxide activated carbons, zeolites, mesoporous molecular sieves MCM-41 type. Freezing discussed methane at 111 K....

With the example of capillary condensation Lennard-Jones fluid in nanopores ranging from 1 to 10 nm, we show that non-local density functional theory (NLDFT) with properly chosen parameters intermolecular interactions bridges scale gap molecular simulations macroscopic thermodynamics. On one hand, NLDFT correctly approximates results Monte Carlo (shift vapour–liquid equilibrium, spinodals, profiles, adsorption isotherms) for pores wider than about 2 nm. other smoothly merges (above 7–10 nm)...

We studied cavitation in metastable fluids drawing on the example of liquid nitrogen confined to spheroidal pores specially prepared well-characterized mesoporous silica materials with mean pore diameters ranging from ∼6 ∼35 nm. Cavitation was monitored process evaporation/desorption fully saturated samples gradually decreasing vapor pressure at isothermal conditions. The onset displayed by a sharp step desorption isotherm. found that depended size for smaller than ∼11 nm and remained...

The microphase segregation in the Nafion (DuPont trademark) perfluorinated membrane at different water contents was studied using molecular dynamics simulations. As degree of solvation increased, we observed formation clusters containing up to ca. 100 molecules. In contrast conventional network models, do not form a continuous hydrophilic subphase. cluster size distribution is rather wide and evolves time due break-up temporary bridges between clusters. This dynamic behavior system allows...

Micellization of surfactant solutions is a ubiquitous phenomenon in natural systems and technological processes, its theoretical description represents one the cornerstone problems physical chemistry colloidal systems. However, successful attempts quantitative modeling confirmed by experimental data remains limited. We show, for first time, that dissipative particle dynamics with rigorously defined soft repulsion interaction rigidity parameters capable predicting micellar self-assembly...

Using dissipative particle dynamics (DPD) simulations, we explore the specifics of micellization in solutions anionic and cationic surfactants their mixtures. Anionic surfactant sodium dodecyl sulfate (SDS) cetyltrimethylammonium bromide (CTAB) are chosen as characteristic examples. Coarse-grained models constructed parameterized using a combination atomistic molecular simulation infinite dilution activity coefficient calibration. Electrostatic interactions charged beads treated smeared...

Molecular mechanics and molecular dynamics simulation studies of conformation solvation perfluorosulfate oligomers, representing fragments Nafion membrane, have been performed. Two typical conformations the oligomer, composed 10 monomer units, found in a vacuum. A stretched geometry fluorocarbon skeleton with tortuosity 2.4 was reached by energy optimization starting from regular all CCCC angles trans position. highly folded spiral-like configuration obtained when randomly bent chain taken...

A method for Monte Carlo studies of phase equilibrium in confined systems is presented using an example vapor-liquid (capillary condensation and evaporation) cylindrical pores. The method, named the gauge cell allows one to construct full diagram a fluid form van der Waals loop, which includes stable, metastable, unstable states. coexistence then determined by thermodynamic integration along metastable regions employing Maxwell's rule equal areas. simulation results agree with experimental...

We present a Monte Carlo (MC) simulation study of capillary condensation and desorption in spherical cavity connected with the bulk phase by cylindrical necks smaller diameter. confirm two mechanisms spontaneous evaporation from and, correspondingly, types adsorption hysteresis, which depend on relation between sizes connecting pores. When are sufficiently wide, is determined conditions neck. This classical ink-bottle or pore blocking effect: controlled size narrow, cavitation stretched...

The solvation of Nafion oligomer in equimolar water−methanol solution was studied by means molecular dynamics simulations. skeleton system found to be substantially folded; its geometry close that pure water. Pronounced flexibility the observed. At same time, side chains turned out very stiff. No conformation transitions were monitored. mostly solvated methanol. A minor preference for water vicinity sulfate group lifetime hydrogen bonds and methanol estimated. lifetimes two components each...

Micelle formation in surfactant solutions is a self-assembly process governed by complex interplay of solvent-mediated interactions between hydrophilic and hydrophobic groups, which are commonly called heads tails. However, the head-tail repulsion not only factor affecting micelle formation. For first time, we present systematic study effect chain rigidity on critical concentration size, performed with dissipative particle dynamics simulation method. Rigidity coarse-grained molecule was...

By means of dissipative particle dynamics (DPD) and Monte Carlo (MC) simulations, we explored geometrical, transport, sorption properties hydrated Nafion-type polyelectrolyte membranes. Composed a perfluorinated backbone with sulfonate side chains, Nafion self-assembles upon hydration segregates into interpenetrating hydrophilic hydrophobic subphases. This segregated morphology determines the transport membranes that are widely used as compartment separators in fuel cells other...

We present a coarse-grained model of the acid form Nafion membrane that explicitly includes proton transport. This is based on soft-core bead representation polymer implemented into dissipative particle dynamics (DPD) simulation framework. The introduced as separate charged forms dissociable Morse bonds with water beads. bond formation and breakup artificially mimics Grotthuss hopping mechanism proposed DPD parameterized to account for specifics conformations flexibility backbone sidechains;...

Liquid−vapor equilibrium, criticality, and spinodal transitions in nanopores are studied by the gauge cell Monte Carlo simulation method proposed recently (Neimark, A. V.; Vishnyakov, Phys. Rev. E 2000, 62, 4611). As an instructive example, we consider capillary condensation of argon cylindrical pores different diameters (1.5−5.5 nm) representing typical pore channels mesoporous molecular sieves. At subcritical conditions, allows one to construct continuous phase diagrams form a van der...

The critical properties of the Lennard-Jones fluid in slitlike pores different widths have been studied by Gibbs ensemble Monte Carlo method and lattice gas model. Graphite up to 10 molecular diameters width similar with weaker solid−fluid interactions considered. Strong layering adsorbate graphite confirmed applicability model such systems. vapor−liquid phase diagrams for confined fluids obtained two methods are reasonable agreement each other. Linear dependence temperature on inverse pore...

Nucleation of liquid bridges and bubbles during condensation evaporation Lennard-Jones fluid in cylindrical pores is explored by Monte Carlo simulation. The isotherm constrained critical nuclei constructed using the gauge cell method. We confirm Everett–Haynes scenario bridging through formation a bump/undulation on adsorption film. molecular structure growing cavitating revealed. A new simulation approach introduced to calculate nucleation energy barriers. method based introduction...

Universal mechanisms of adsorption and capillary condensation toluene nitrogen on ordered MCM-41 PHTS materials are studied by means high-resolution experiments Monte Carlo molecular simulations. A simulation model in silica nanopores, which accounts for surface heterogeneity, a hybrid molecular-macsroscopic method pore size distribution (PSD) calculations have been developed. For range reference materials, the PSD results obtained from isotherms consistent with using nonlocal density...

Phase transformations in fluids confined to nanoscale pores, which demonstrate characteristic signatures of first-order phase transitions, have been extensively documented experiments and molecular simulations. They are characterized by a pronounced hysteresis, disappears above certain temperature. A rigorous interpretation these observations represents fundamental problem from the point view statistical mechanics. Nanoscale systems essentially small, finite volume systems, concept...

Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer are modeled by coarse-grained beads interacting via short-range soft repulsion smeared charge electrostatic potentials. is introduced as separate charged bead...

This paper presents a consistent strategy for parametrization of coarse-grained models chain molecules in dissipative particle dynamics (DPD), where the soft-core DPD interaction parameters are fitted to activities solutions reference compounds that represent different fragments target molecules. The intercomponent matched either infinite dilution activity coefficients binary or solvent polymer solutions. respective calibration relationships between and parameter constructed from results...

We study the equilibrium and stability of metastable states capillary condensation hysteresis a Lennard-Jones fluid in cylindrical pores by means canonical ensemble density functional theory gauge cell Monte Carlo simulations. demonstrate possibility for existence multiple laterally uniform internal equal inside loop. The region is bounded zero compressibility. can be stabilized simulations constraining fluctuations.

We study the nucleation of a bubble in metastable Lennard-Jones (LJ) fluid, confined to spherical pore with wetting walls, by combination grand canonical, canonical ensemble, and gauge cell Monte Carlo simulation methods complemented Voronoi-Delaunay tessellation analysis statistical geometry intermolecular cavities. construct isotherm fluid form continuous van der Waals' loop, which unstable backward trajectory between spinodals corresponds states. show that as degree metastability...

Polyelectrolyte membranes (PEM) such as Nafion (Du Pont) used compartment separators in fuel cells and other electro-chemical applications are also of interest permselective diffusion barriers protective fabrics. By means sorption permeation experiments conjunction with molecular dynamics simulations, we explore the permeability membrane to water hydrophilic solvents 1-propanol dimethyl methylphosphonate, focusing on relationship between polymer structure, solvation, solvent diffusion. It is...

Single crystal rubrene is a model organic electronic material showing high carrier mobility and long exciton lifetime. These properties are detrimentally affected when exposed to intense light under ambient conditions for prolonged periods of time, possibly due oxygen up-take. Using photoelectron, scanning probe ion-based methods, combined with an isotopic exposure, we present direct evidence the light-induced reaction molecular single rubrene. Without significant exposure light, there no...