MOLECULAR-DYNAMICS STUDY ON THE COLLAPSE OF A-TYPE ZEOLITE FRAMEWORK .2. PREDICTION OF THE STRUCTURAL TRANSFORMATION BY FITTING THE RADIAL-DISTRIBUTION FUNCTIONS

Molecular dynamics (MD) calculations for A-type zeolite are carried out at several temperatures and the radial distribution functions (rdf) are obtained at those temperatures. Using the rdf of the 625 K structures for A-type zeolite and cristobalite-type structure selected as the standard structures, we obtain their relative proportions by rdf fitting at several temperatures. According to our findings, the A-type zeolite starts to collapse around 900 K and, at 1800 K, nearly 50% of the A-type zeolite transforms into the cristobalite-type structure. This transformation is maximized at 2400 K and the cristobalite-type structure also starts to collapse above this temperature. Though the temperatures where characteristic structural changes are found are higher than the experimental results, the rdf fitting method is successfully applied to the prediction of the structural transformation of A-type zeolite into the cristobalite-type structure. © 1990 American Chemical Society.