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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 14, Number 3
BKCSDE 14(3)
March 20, 1993 

Molecular Dynamics Simulation Studies of Zeolite-A. Ⅱ. Structure and Dynamics of Cations in Dehydrated Ca2+-Exchanged Zeolite-A
Gyeong Keun Moon, Sang Gu Choi, Han Soo Kim, Song Hi Lee*
In a recent paper we reported molecular dynamics (MD) simulation of Na+ ions in a rigid dehydrated zeolite-A framework at several temperatures using a simple Lennard-Jones potential plus Coulomb potential with Ewald summation to investigate the structure and dynamics of Na+ ions. In this paper the same technique is applied to study the structre and dynamics of cations in dehydrated Ca2+-exchanged zeolite-A systems, Ca6-A and Ca4Na4-A. At 298.15 K the calculated positions of Ca2+ and Na+ ions are in poor agreement with those determined by X-ray diffraction experiments, but this is reasonably explained by large repulsive interactions between cations. A simple harmonic oscillation of Ca2+ ions in dehydrated Ca6-A zeolite and simultaneous random motions for the the same kinds of cations in dehydrated Ca4Na4-A zeolite due to a positional symmetry are observed in their velocity auto-correlation functions and mean square displacements. MD simulations of the fictitious Ca8-A zeolite confirm our result for the behavior of Ca2+ ions in dehydrated Ca6-A zeolite.
356 - 362
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