A theory for self-diffusion in liquids

We propose an alternative approach to self-diffusion in an atomic liquid. O ur starting point is an oscillatory motion of a tagged particle in its firs t solvation shell (cage). Only after cage relaxation is taken into account is the tagged particle able to diffuse. This approach is suitable for descr ibing liquids where the concept of binary collisions breaks down and the se lf-diffusion coefficient is small. Our predictions quantitatively agree wit h the results of MD simulations in a broad range of densities and temperatu res up to the freezing transition. (C) 1999 American Institute of Physics. [S0021-9606(99)50606-5].