Abstract
The form of the double Fourier transform S(k, omega ) of the occupancy correlation function of an atom diffusion in a cubic crystal by the vacancy mechanism has recently been derived by Tahir-Kheli and Elliott (1982). It is shown that their results may be obtained more simply from the encounter model using known values of the atom displacement probability due to an atom-vacancy encounter. Results for the full width at half maximum of the spherically averaged S(k, omega ) are calculated for the mean field theory and for the encounter model.