Diffusion in zeolites: Anomalous dependence on sorbate diameter

Yashonath, S.; Santikary, Prakriteswar

doi:10.1063/1.466336

Cited by 48 publications

(44 citation statements)

References 13 publications

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“…The intensity of the peak for the flexible framework calculation is somewhat lower than that obtained for rigid cage. 10 The anomalous behavior of k, is more pronounced as compared to that of D. Behavior of the rate of cage visits, k, is similar to that of D and hence is not shown in Figure 3. The results shown in Figure 3 clearly suggest that the anomalous behavior or ring effect exists even when the framework flexibility is included.…”

Section: Ring Effect or Diffusion Anomalymentioning

confidence: 70%

Dynamics of Zeolite Cage and Its Effect on the Diffusion Properties of Sorbate: Persistence of Diffusion Anomaly in NaA Zeolite

Santikary¹,

Yashonath²

1994

J. Phys. Chem.

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Recent computer simulations on zeolites Y and A have found that the diffusion coefficient and the rate of intercage diffusion exhibit, apart from a linear dependence on the reciprocal of the square of the sorbate diameter, a n anomalous peak as sorbate diameter approaches the window diameter. Here we report molecular dynamics simulations of zeolite NaA incorporating framework flexibility as a function of sorbate diameter in order to verify the existence of anomalous diffusion. Results suggest persistence of anomalous diffusion or ring effect. This suggests that the anomalous behavior is a general effect characteristic of zeolites Y and A. The barrier for diffusion across the eight-ring window is seen to be negative and is found to decrease with sorbate size. The effect of sorbate on the cage motion has also been investigated. Results suggest that the window expands during intercage migration only if the sorbate size is comparable to the window diameter. Flexible cage simulations yield a higher value for the diffusion coefficient and also the rate of intercage diffusion. This increase has been shown to be due to an increase in the intercage diffusions via the centralized diffusion mode rather than the surface-mediated mode. It is shown that this increase arises from a n increase in the single particle density distribution in the region near the cage center.

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Section: Ring Effect or Diffusion Anomalymentioning

confidence: 70%

Dynamics of Zeolite Cage and Its Effect on the Diffusion Properties of Sorbate: Persistence of Diffusion Anomaly in NaA Zeolite

Santikary¹,

Yashonath²

1994

J. Phys. Chem.

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“…Yashonath and co-workers [375][376][377][378][379] observed in MD simulations of noble gases in zeolite A (LTA) and Y (FAU) an increase of the diffusion coefficient as a function of the diameter of the noble gas. This effect was denoted the levitation effect.…”

Section: Resonance Diffusionmentioning

confidence: 99%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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“…This feature also leads the Oscillator model to theoretically predict levitation or superdiffusive behaviour (Kumar and Bhatia, 2006), evidenced in molecular dynamics simulations (Yashonath and Santikary, 1994), in which a maximum in diffusivity with pore size or with diffusant molecular size is observed. This behaviour, which cannot be predicted by the Knudsen theory, has now been experimentally verified by direct microscopic measurements (Jobic et al, 2009), providing strong evidence for the importance of the dispersive interactions on the transport.…”

Section: Article In Pressmentioning

confidence: 88%