Self-diffusivity and velocity autocorrelation functions for xenon in NaY using memory kernels

Abstract

The applicability of the memory function formalism to the study of the dynamics of rare gas atoms in zeolite NaY is assessed. Solutions to the memory equation are obtained by solving the memory kernel with different analytic closure schemes. Inputs to the models are the frequency moments, which are obtained from molecular dynamics simulations. The model predictions are compared with the results obtained using molecular dynamics simulations for Xe in zeolite NaY at loadings of one atom/cage at different temperatures. Predictions from the secant hyperbolic memory kernel were found to yield the most accurate of the various models investigated, with quantitative predictions above temperatures of 300 K. Since the frequency moments can be computed in a Monte Carlo simulation, the method outlined here suggests an alternate route to the dynamics of confined fluids.

Keywords:

• Self-diffusivity
• Velocity autocorrelation functions
• Xenon
• NaY
• Memory kernels

Acknowledgements

We would like to thank C. R. Kamala for assisting with the molecular dynamics simulations, and Scott Auerbach and S. Yashonath for useful discussions during this work.