The coupled phonon-lattice gas model is used to calculate the frequenc
y dependent hopping rate of mobile ions in superionic conductors. It i
s found that the hopping rate is composed of several Gaussians includi
ng both contributions of the ion-phonon and ion-ion interactions. The
calculated hopping rate is compared with the far infra-red conductivit
y for silver halides, AgI, AgCl and AgBr.