  Ion-conducting glasses and polymer systems show several characteristic
peculiarities in their composition-dependent diffusion properties and in their
dynamic response. First we give a brief review of the current understanding of
the ion dynamics in network glasses in terms of stochastic theories. Secondly,
a model for PEO(polyethylene-oxide)-based polymer electrolytes is described.
The equation of state is calculated from the quasichemical approximation. Using
this information together with Monte Carlo simulations of diffusion at constant
volume, we obtain constant-pressure results for polymer chain and ion diffusion
as a function of ion concentration. This theory allows us to make comparison
with experiments which are carried out at constant pressure.
