NORMAL, SINGLE-FILE, AND DUAL-MODE DIFFUSION OF BINARY ADSORBATE MIXTURES IN ALPO4-5

We have used molecular simulations to examine the diffusion of Ne, Ar, Kr, Xe, CH4, CF4, CCl4, SF6, SnCl4, and SnBr4 in the molecular sieve AlPO4-5, both as single species and as coadsorbed mixtures. Single ads orbed species exhibit a transition from normal to single-file diffusio n as a function of increasing adsorbate size. In addition to normal an d single-file diffusion, coadsorbed mixtures exhibit a qualitatively n ew diffusion mode in which one species performs normal diffusion while the other undergoes single-file diffusion. We discuss the prospects f or experimental verification of this phenomenon, and present measureme nts of the loading dependence of diffusion rates during the dual-mode diffusion of Ne/CF4 mixtures. (C) 1997 American Institute of Physics.