Short-range order in cylindrical liquid-filled micropores

Analytical theories for lattice adsorption and diffusion recently published are tested with molecular dynamics (MD) simulations. Our analytical theories are generalized and can be applied to various small molecules in different nanoporous structures such as zeolites and molecular sieves. In this work, we validate our theory by comparing the results with those predicted by simulations. We study the behavior of methane in zeolite Na-Y. Specifically, the MD simulations are conducted to obtain the interaction energies and self-diffusion coefficients at five different temperatures and loadings. While the lattice adsorption theory incorporates minimum parameters to obtain the thermodynamic properties, the diffusion component of the theory incorporates no adjustable parameters. Our theory is in very good qualitative agreement with the simulations. Overall, reasonably good quantitative agreement is found between the theory and simulations. Our theory studies the effect of temperature and density on the adsorption and diffusion of methane in Na-Y. Our theory requires approximately only a minute to obtain the results, as compared with the tens of CPU hours required for simulations.

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“…A significant body of literature has been devoted to investigating the phenomenon of adsorption and diffusion in nanoporous materials. − …”

Section: Introductionmentioning

confidence: 99%

Agreement between Analytical Theory and Molecular Dynamics Simulation for Adsorption and Diffusion in Crystalline Nanoporous Materials

2003

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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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“…14,15 However, besides computer simulations (see, e.g., Refs. [16][17][18][19][20], different analytical approaches exist requiring approximations or even numerical solutions. Without attempting completeness, we mention the transfer-matrix method (see, e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of quasi-one-dimensional fluids

Franosch,

Schilling

2024

The Journal of Chemical Physics

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We calculate thermodynamic and structural quantities of a fluid of hard spheres of diameter σ in a quasi-one-dimensional pore with accessible pore width W smaller than σ by applying a perturbative method worked out earlier for a confined fluid in a slit pore [Franosch et al. Phys. Rev. Lett. 109, 240601 (2012)]. In a first step, we prove that the thermodynamic and a certain class of structural quantities of the hard-sphere fluid in the pore can be obtained from a purely one-dimensional fluid of rods of length σ with a central hard core of size σW=σ2−W2 and a soft part at both ends of length (σ − σW)/2. These rods interact via effective k-body potentials veff(k) (k ≥ 2). The two- and the three-body potential will be calculated explicitly. In a second step, the free energy of this effective one-dimensional fluid is calculated up to leading order in (W/σ)2. Explicit results for, e.g., the perpendicular pressure, surface tension, and the density profile as a function of density, temperature, and pore width are presented and partly compared with results from Monte-Carlo simulations and standard virial expansions. Despite the perturbative character of our approach, it encompasses the singularity of the thermodynamic quantities at the jamming transition point.

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Short-range order in cylindrical liquid-filled micropores

Cited by 11 publications

References 30 publications

Agreement between Analytical Theory and Molecular Dynamics Simulation for Adsorption and Diffusion in Crystalline Nanoporous Materials

Agreement between Analytical Theory and Molecular Dynamics Simulation for Adsorption and Diffusion in Crystalline Nanoporous Materials

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

Thermodynamic properties of quasi-one-dimensional fluids

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