DIFFUSION IN MULTICOMPONENT LIQUIDS - A NEW SET OF COLLECTIVE VELOCITY CORRELATION-FUNCTIONS AND DIFFUSION-COEFFICIENTS

A new set of time correlation functions for the description of the mic roscopic collective dynamic behavior in multicomponent liquids is intr oduced. These functions, the relative mean molecular velocity correlat ions, are independent of the considered reference frame and the relate d diffusion coefficients may be defined. The advantages of this kind o f description are discussed and relations between the proposed diffusi on coefficients and both phenomenological and empirical transport coef ficients are derived. Special attention is devoted to the binary liqui ds.