Molecular Simulation of Loading Dependent Slow Diffusion in Confined Systems

Beerdsen, E.; Smit, Berend; Dubbeldam, David

doi:10.1103/physrevlett.93.248301

Cited by 119 publications

(194 citation statements)

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“…The conversion of the hopping rate at nonzero loading is therefore the same as for the infinite dilution case. Importantly, the study of diffusion over long time and space regions can then be restricted to the analysis of the free energy profiles of a single unit cell (the surrounding cages influence this profile and have to be properly modeled 29 ). For the same system, methane in LTA-type silica, the dcTST method of Beerdsen et al gives exact overlap with MD results (see Figure 3 …”

Section: Methodsmentioning

confidence: 99%

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Dynamically Corrected Transition State Theory Calculations of Self-Diffusion in Anisotropic Nanoporous Materials

et al. 2006

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We apply the dynamically corrected transition state theory to confinements with complex structures. This method is able to compute self-diffusion coefficients for adsorbate-adsorbent systems far beyond the time scales accessible to molecular dynamics. Two example cage/window-type confinements are examined: ethane in ERI-and CHA-type zeolites. In ERI-type zeolites, each hop in the z direction is preceded by a hop in xy direction and diffusion is anisotropic. The lattice for CHA-type zeolite is a rhombohedral Bravais lattice, and diffusion can be considered isotropic in practice. The anisotropic behavior of ERI-type cages reverses with loading, i.e., at low loading the diffusion in the z direction is two times faster than in the xy direction, while for higher loadings this changes to a z diffusivity that is more than two times slower. At low loading the diffusion is impeded by the eight-ring windows, i.e., the exits out of the cage to the next, but at higher loadings the barrier is formed by the center of the cages.

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Section: Methodsmentioning

confidence: 99%

“…26,29 We used the velocity Verlet integration scheme with a time step of 0.5 fs. The relative energy drift was smaller than 10 -4 .…”

Section: Of Ref 29)mentioning

confidence: 99%

Dynamically Corrected Transition State Theory Calculations of Self-Diffusion in Anisotropic Nanoporous Materials

et al. 2006

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“…The NVT ensemble was imposed using a Nosé-Hoover thermostat. Free-energy profiles were obtained from Monte Carlo simulations using the "histogram method" described in ref 32. The simulation box sizes for the various simulated systems are given in Table 1.…”

Section: In This Equation D Smentioning

confidence: 99%

“…Making use of the periodicity of nanoporous materials, we use a lattice point only as the integration region in the dcTST method to obtain a diffusion coefficient. 32 …”

Section: Zeolite Structuresmentioning

confidence: 99%

“…[29][30][31] Only recently, a dynamically corrected transition-state theory method (dcTST) has been developed that can be applied to study diffusion in confined systems beyond the infinite dilution limit. 32 This method can provide a molecular explanation for diffusion behavior in terms of free energy. 33,34 Armed with this method, we can now take a more generalized look on diffusion in confined systems.…”

Section: Introductionmentioning

confidence: 99%

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Loading Dependence of the Diffusion Coefficient of Methane in Nanoporous Materials

2006

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In this work, we use molecular simulations to study the loading dependence of the self-and collective diffusion coefficients of methane in various zeolite structures. To arrive at a microscopic interpretation of the loading dependence, we interpret the diffusion behavior in terms of hopping rates over a free-energy barrier. These free-energy barriers are computed directly from a molecular simulation. We show that these free-energy profiles are a convenient starting point to explain a particular loading dependence of the diffusion coefficient. On the basis of these observations, we present a classification of zeolite structures for the diffusion of methane as a function of loading: three-dimensional cagelike structures, one-dimensional channels, and intersecting channels. Structures in each of these classes have their loading dependence of the free-energy profiles in common. An important conclusion of this work is that diffusion in nanoporous materials can never be described by one single effect so that we need to distinguish different loading regimes to describe the diffusion over the entire loading range.

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Computer Simulation of Sorption and Transport in Zeolites

Papadopoulos

Theodorou

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Reconstruction of Zeolitic Media Atomistic Reconstruction Mesoscopic Reconstruction A Stochastic B Particle‐Based Zeolite Force Field Sorption Equilibria Sorbate Dynamics Methodology Survey of Dynamics Simulation Studies A Intracrystalline Dynamics B Intercrystalline Dynamics Conclusions

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Molecular Simulation of Loading Dependent Slow Diffusion in Confined Systems

Cited by 119 publications

References 22 publications

Dynamically Corrected Transition State Theory Calculations of Self-Diffusion in Anisotropic Nanoporous Materials

Dynamically Corrected Transition State Theory Calculations of Self-Diffusion in Anisotropic Nanoporous Materials

Loading Dependence of the Diffusion Coefficient of Methane in Nanoporous Materials

Computer Simulation of Sorption and Transport in Zeolites

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