Self-diffusion, interdiffusion and long wavelength plasma oscillations in binary ionic mixtures

The self-diffusion and interdiffusion of the two ionic species in binary mixtures of point ions immersed in a uniform neutralizing background are analyzed on the basis of molecular dynamics simulations over a wide range of couplings. The autocorrelation function associated with interdiffusion is well approximated by a well-defined linear combination of the two velocity autocorrelation functions. The results are then used to determine the plasmon frequency and lifetime in the long wavelength limit. While the frequency of the infinite wavelength plasmon mode rises only slowly with coupling above the usual kinetic plasma frequency, collisional damping turns out to be very important at strong couplings.