Capillary Condensation in Pores with Energetically Heterogeneous Walls: Density Functional versus Monte Carlo Calculations

Reszko-Zygmunt, Joanna; Pizio, Orest; Rżysko, W.; Sokołowski, S.; Sokołowska, Z.

doi:10.1006/jcis.2001.7721

Cited by 20 publications

(19 citation statements)

References 21 publications

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“…As previously, for each temperature, the total coverage is calculated by integrating the local density, and the complete coexistence diagram is drawn in Fig. [41][42][43][44] As a consequence of the stabilization of the bridgelike phase, two apparent critical temperatures are now visible. For comparison the coexistence diagram of the fluid confined in the perfectly cylindrical pore is also given ͑circles͒.…”

Section: Chemical Undulation and The Bridge Phasementioning

confidence: 99%

Phase coexistence in heterogeneous porous media: A new extension to Gibbs ensemble Monte Carlo simulation method

Puibasset

2005

The Journal of Chemical Physics

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The effect of confinement on phase behavior of simple fluids is still an area of intensive research. In between experiment and theory, molecular simulation is a powerful tool to study the effect of confinement in realistic porous materials, containing some disorder. Previous simulation works aiming at establishing the phase diagram of a confined Lennard-Jones-type fluid, concentrated on simple pore geometries (slits or cylinders). The development of the Gibbs ensemble Monte Carlo technique by Panagiotopoulos [Mol. Phys. 61, 813 (1987)], greatly favored the study of such simple geometries for two reasons. First, the technique is very efficient to calculate the phase diagram, since each run (at a given temperature) converges directly to an equilibrium between a gaslike and a liquidlike phase. Second, due to volume exchange procedure between the two phases, at least one invariant direction of space is required for applicability of this method, which is the case for slits or cylinders. Generally, the introduction of some disorder in such simple pores breaks the initial invariance in one of the space directions and prevents to work in the Gibbs ensemble. The simulation techniques for such disordered systems are numerous (grand canonical Monte Carlo, molecular dynamics, histogram reweighting, N-P-T+test method, Gibbs-Duhem integration procedure, etc.). However, the Gibbs ensemble technique, which gives directly the coexistence between phases, was never generalized to such systems. In this work, we focus on two weakly disordered pores for which a modified Gibbs ensemble Monte Carlo technique can be applied. One of the pores is geometrically undulated, whereas the second is cylindrical but presents a chemical variation which gives rise to a modulation of the wall potential. In the first case almost no change in the phase diagram is observed, whereas in the second strong modifications are reported.

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Section: Chemical Undulation and The Bridge Phasementioning

confidence: 99%

Phase coexistence in heterogeneous porous media: A new extension to Gibbs ensemble Monte Carlo simulation method

Puibasset

2005

The Journal of Chemical Physics

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“…Several recent studies have carried out MC simulations of capillarity at the molecular and nanometer scale in pores. However, these systems are strongly influenced by thermal fluctuations and have also focused on simple pore geometries such as slits and cylinders [e.g., Albano et al , 1997; Reszko‐Zygmunt et al , 2001; Cao and Wang , 2001; Gelb , 2002; Coasne and Pellenq , 2004; Paul and Rieger , 2005]. Furthermore, such microscopic approaches must be scaled‐up to predict macroscopic properties of a composite like soils.…”

Section: Introductionmentioning

confidence: 99%

A Monte Carlo paradigm for capillarity in porous media

Zeidman

Lusk

et al. 2010

Geophysical Research Letters

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[1] Wet porous media are ubiquitous in nature as soils, rocks, plants, and bones, and in engineering settings such as oil production, ground stability, filtration and composites. Their physical and chemical behavior is governed by the distribution of liquid and interfaces between phases. Characterization of the interfacial distribution is mostly based on macroscopic experiments, aided by empirical formulae. We present an alternative computational paradigm utilizing a Monte Carlo algorithm to simulate interfaces in complex realistic pore geometries. The method agrees with analytical solutions available only for idealized pore geometries, and is in quantitative agreement with Micro X-ray Computed Tomography (microXCT), capillary pressure, and interfacial area measurements for natural soils. We demonstrate that this methodology predicts macroscopic properties such as the capillary pressure and air-liquid interface area versus liquid saturation based only on the pore size information from microXCT images and interfacial interaction energies. The generality of this method should allow simulation of capillarity in many porous materials. Citation:

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“…This problem may be overcome by introducing the energetic heterogeneity of the pore wall surface or random distribution of the pore wall thickness . The importance of the energetic heterogeneity of the pore surface was long recognized in the literature. − Some authors model surface heterogeneity by introducing a potential with a periodic spatial variation, − while others use the patchwise model. , In this paper, we account for the energetic heterogeneity of adsorbents in the framework of the patchwise model of the surface. The energetic heterogeneity is described by a distribution function with respect to the solid−fluid potential well depth.…”

Section: Introductionmentioning

confidence: 99%

Application of Density Functional Theory to Analysis of Energetic Heterogeneity and Pore Size Distribution of Activated Carbons

Ustinov

2004

Langmuir

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A new approach based on the nonlocal density functional theory to determine pore size distribution (PSD) of activated carbons and energetic heterogeneity of the pore wall is proposed. The energetic heterogeneity is modeled with an energy distribution function (EDF), describing the distribution of solid-fluid potential well depth (this distribution is a Dirac delta function for an energetic homogeneous surface). The approach allows simultaneous determining of the PSD (assuming slit shape) and EDF from nitrogen or argon isotherms at their respective boiling points by using a set of local isotherms calculated for a range of pore widths and solid-fluid potential well depths. It is found that the structure of the pore wall surface significantly differs from that ofgraphitized carbon black. This could be attributed to defects in the crystalline structure of the surface, active oxide centers, finite size of the pore walls (in either wall thickness or pore length), and so forth. Those factors depend on the precursor and the process of carbonization and activation and hence provide a fingerprint for each adsorbent. The approach allows very accurate correlation of the experimental adsorption isotherm and leads to PSDs that are simpler and more realistic than those obtained with the original nonlocal density functional theory.

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Capillary Condensation in Pores with Energetically Heterogeneous Walls: Density Functional versus Monte Carlo Calculations

Cited by 20 publications

References 21 publications

Phase coexistence in heterogeneous porous media: A new extension to Gibbs ensemble Monte Carlo simulation method

Phase coexistence in heterogeneous porous media: A new extension to Gibbs ensemble Monte Carlo simulation method

A Monte Carlo paradigm for capillarity in porous media

Application of Density Functional Theory to Analysis of Energetic Heterogeneity and Pore Size Distribution of Activated Carbons

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