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Cryogenic helium adsorbed in zeolite rho: Inside localization controlled self-diffusion of confined quantum particles
Journal article   Peer reviewed

Cryogenic helium adsorbed in zeolite rho: Inside localization controlled self-diffusion of confined quantum particles

Piotr Kowalczyk, Piotr A. Gauden, Artur P. Terzyk, Sylwester Furmaniak and Katsumi Kaneko
Journal of Physical Chemistry. C, Vol.115(37), pp.18105-18110
2011
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Abstract

Adsorption Energy Fluids Kinetics Zeolites
Applying Feynman's treatment of quantum mechanics at finite temperatures via path integrals and the numerical analytic continuation method developed recently (Kowalczyk, P.; Gauden, P. A; Terzyk, A. P.; Furmaniak, Sylwester, J. Chem. Theory Comput. 2009, 5, 1990-1996), we study the mobility of He-4 atoms adsorbed in zeolite rho at 40 K At studied temperature, the self-diffusive motion of He-4 atoms in zeolite rho is strongly concentration-dependent. At low pore concentrations, He-4 atoms are adsorbed in high-energetic adsorption centers of the zeolite. Due to strong localization in the solid fluid potential well, an average kinetic energy of He-4 atoms at infinite dilution reaches similar to 120 K (i.e., twice of the dassical kinetic energy at 40 K, E-class = 60K), whereas the self-diffusion constant drops up to similar to 0.001 angstrom(2) ps(-1). Increasing pore concentration of He-4 leads to the rapid increase in mobility of adsorbed He-4 atoms. We show that similar to 8 mmol cm(-3), self-diffusive motion of confined He-4 atoms increases up to similar to 1 angstrom(2) ps(-1). Variation of the kinetic energy, potential energy, and enthalpy of 4He adsorption with pore concentration indicates that high-energetic adsorption sites in studied zeolite sample are saturated at low pore densities. The remaining adsorption sites are characterized by weaker solid fluid potential, which allows higher delocalization of adsorbed He-4 atoms. The reported novel phenomenon of localization controlled self-diffusion of confined He-4 seems to be promising for smart designing of nanoporous quantum molecular sieves and storage nanovessels. Understanding of He-4 cryogenic adsorption in the smallest pores enriches our knowledge that is crucial for precise analysis of ultramicropore sizes.

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Collaboration types
Domestic collaboration
International collaboration
Citation topics
2 Chemistry
2.15 Physical Chemistry
2.15.90 Photodissociation
Web Of Science research areas
Chemistry, Physical
Materials Science, Multidisciplinary
Nanoscience & Nanotechnology
ESI research areas
Chemistry
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