Fluid behaviour in narrow pores

Peterson, Brian K.; Walton, Jeremy; Gubbins, Keith E.

doi:10.1039/f29868201789

Cited by 160 publications

(92 citation statements)

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“…Simulations have been used to study fluids adsorbed in slit pores (Sarman, 1990;Somers and Davis, 1992;Murad et al, 1993;Han et al, 1993;Tan and Gubbins, 1992;Somers et al, 1993;Schoen et al, 1989;Jiang et al, 1993), cylindrical pores Suh, 1987, 1989;Groot et al, 1987;Antonchenko et al, 1988;Bratko et al, 1989;Heinbuch and Fischer, 1987;Glandt, 1980;Derouane and Lucas, 1988;Peterson et al, 1986;Peterson and Gubbins, 1987;Walton and Quirke, 1989;Saito and Foley, 1990;Demi, 1991), and spherical pores (Macpherson et al, 1987;Carignan et al, 1988;Dunne and Myers, 1994).…”

Section: Introductionmentioning

confidence: 99%

The effect of nanopore shape on the structure and isotherms of adsorbed fluids

1996

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A Grand Canonical Monte Carlo simulation method is used to determine the adsorption isotherms, interaction energies, entropies, and density distribution of a Lennard-Jones fluid adsorbed in smooth-walled nanopores of varying size and shape. We specifically include very crowded pores, where packing effects are important. Differences in the isotherms of slit, cylindrical, and spherical nanopores of varying sizes can be explained in terms of the adsorbate-adsorbate interaction energy, the adsorbate-pore interaction energy, and the density profiles, which influence the balance between the former and the latter energy contributions. The expectation from low loading studies that the most energetically favorable adsorbate-pore interactions maximize adsorption is not borne out at intermediate and higher loadings. Instead, the relationships between adsorbed amounts and pore size and shape are found to be strong functions of the depth and steepness of the external potential, the extent to which adsorbateadsorbate repulsion establishes short range fluid order, and the accessible pore volume. This study has implications for high pore density processes in nanoporous materials, such as zeolite catalysis, separations, and templating in zeolite synthesis.

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Section: Introductionmentioning

confidence: 99%

The effect of nanopore shape on the structure and isotherms of adsorbed fluids

1996

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“…In our simulations V w is shifted and cut at a distance z cut = 9 Å from the wall. An analogous integration can be performed over the volume surrounding an infinitely long pore with radius R p yielding a semianalytical solution ͑see the work of Peterson et al 23 or Appendix A in the work of Allen et al 10 ͒ given by…”

Section: Appendix A: Water-wall and Water Cylinder Interactionsmentioning

confidence: 99%

“…The same LJ potential is integrated over the volume confining an infinitely long cylindrical cavity to determine the radial interaction potential V p ͑r͒ between the pore surface and the particles inside the cylindrical pore. 23 An interpolation procedure, described in Appendix A, is applied at the pore edges to avoid any discontinuities. A similar procedure is used to determine the surface-ion potential, and the resulting parameters of the 9-3 potential are summarized in Table I.…”

Section: ͔ ͑1͒mentioning

confidence: 99%

Electric-field-controlled water and ion permeation of a hydrophobic nanopore

Dzubiella¹,

Hansen²

2005

The Journal of Chemical Physics

171

193

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The permeation of hydrophobic, cylindrical nanopores by water molecules and ions is investigated under equilibrium and out-of-equilibrium conditions by extensive molecular-dynamics simulations. Neglecting the chemical structure of the confining pore surface, we focus on the effects of pore radius and electric field on permeation. The simulations confirm the intermittent filling of the pore by water, reported earlier under equilibrium conditions for pore radii larger than a critical radius R c . Below this radius, water can still permeate the pore under the action of a strong electric field generated by an ion concentration imbalance at both ends of the pore embedded in a structureless membrane. The water driven into the channel undergoes considerable electrostriction characterized by a mean density up to twice the bulk density and by a dramatic drop in dielectric permittivity which can be traced back to a considerable distortion of the hydrogen-bond network inside the pore. The free-energy barrier to ion permeation is estimated by a variant of umbrella sampling for Na + , K + , Ca 2+ , and Cl − ions, and correlates well with known solvation free energies in bulk water. Starting from an initial imbalance in ion concentration, equilibrium is gradually restored by successive ion passages through the water-filled pore. At each passage the electric field across the pore drops, reducing the initial electrostriction, until the pore, of radius less than R c , closes to water and hence to ion transport, thus providing a possible mechanism for voltage-dependent gating of hydrophobic pores.

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“…Thus, no long-range correction was attempted. For the pore potential, we used that for the cylindrical pore surrounded by a semi-infinite solid, which was derived by Peterson et al (Peterson et al 1986) with a cylindrical coordinate integration. At a radial position r, the interaction between a fluid particle and the pore wall with radius R is given as follows:…”

Section: Simulation With Imaginary Bulk Vapor Phasementioning

confidence: 99%

Freezing of Lennard-Jones fluid in cylindrical nanopores under tensile conditions

Kanda

Miyahara

2007

Adsorption

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We have shown the Lennard-Jones (LJ) phase diagram for a slit-shaped nanopore by molecular simulations and thermodynamically predicted the results with no adjustable parameter. With this success, LJ phase diagrams are predictable. In this study, the freezing of an LJ CH 4 capillary condensate under a tensile condition in a nonstructural carbon nanopore with a cylindrical geometry was examined using molecular dynamics (MD) simulation. We employ a unit cell in contact with a bulk vapor phase, which is useful for the determination of the bulk vapor pressure in equilibrium with the molecules in a pore. The MD simulation results show liquid-solid (amorphous) phase transitions with a variation in the bulk vapor pressure. The frozen particles are arranged in concentric circular regions along the wall similar to those reported by Maddox and Gubbins. The freezing points are determined from the variations in density, enthalpy, arrangement, and structural functions. The obtained liquid-solid coexistence points are found to exhibit a significant dependence of the freezing point on the equilibrium bulk vapor pressure, forming an extraordinarily skewed curve on the p-T diagram, in contrast to the bulk phase coexistence that is represented by an almost vertical line. The origin of the significant dependence is considered to be the Laplace effect on the capillary condensate similar to the case with a slit-shaped pore. A simple model, which the authors H. Kanda ( ) Energy Engineering

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Fluid behaviour in narrow pores

Cited by 160 publications

References 0 publications

The effect of nanopore shape on the structure and isotherms of adsorbed fluids

The effect of nanopore shape on the structure and isotherms of adsorbed fluids

Electric-field-controlled water and ion permeation of a hydrophobic nanopore

Freezing of Lennard-Jones fluid in cylindrical nanopores under tensile conditions

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