Langevin and fOkker-Planck analyses of inhibited molecular passing processes controlling transport and reactivity in nanoporous materials

Inhibited passing of reactant and product molecules within the linear pores of nanoporous catalytic materials strongly reduces reactivity. The dependence of the passing propensity P on pore radius R is analyzed utilizing Langevin dynamics to account for solvent effects. We find that P ∼ (R-R(c))(σ),...

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Bibliographic Details
Published in:Physical review letters 2014-07, Vol.113 (3), p.038301-038301, Article 038301
Main Authors: Wang, Chi-Jen, Ackerman, David M, Slowing, Igor I, Evans, James W
Format: Article
Language:English
Subjects:
Catalysts
Conformal mapping
Degrees of freedom
Diffusion
Elongation
MATERIALS SCIENCE
Mathematical analysis
Models, Chemical
Nanopores
Nanostructure
Porosity
Reduction
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Summary:Inhibited passing of reactant and product molecules within the linear pores of nanoporous catalytic materials strongly reduces reactivity. The dependence of the passing propensity P on pore radius R is analyzed utilizing Langevin dynamics to account for solvent effects. We find that P ∼ (R-R(c))(σ), where passing is sterically blocked for R≤R(c), with σ below the transition state theory value. Deeper insight comes from analysis of the corresponding high-dimensional Fokker-Planck equation, which facilitates an effective small-P approximation, and dimensional reduction enabling utilization of conformal mapping ideas. We analyze passing for spherical molecules and also assess the effect of rotational degrees of freedom for elongated molecules.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.113.038301