MUTUAL DIFFUSION IN BINARY-SYSTEMS

Expressions for the second and fourth sum rules of relative and cross velocity correlation functions are derived for two component systems. These sum rules and Mori's memory function formalism have been used to study the mutual, self-and distinct diffusion in equimolar Ar-Kr mixt ure and molten salts. It is found that distinct diffusion, which is a measure of effect of cross correlations representing momentum spread t o neighbouring particles, is positive for Ar-Kr mixture and is negativ e for molten salts. These findings are in agreement with molecular dyn amics predictions. The positive value of distinct diffusion was not ac counted for by Darken's and common force models. (C) 1998 American Ins titute of Physics.