  We present results of molecular dynamics simulations on lithium metasilicate
over a broad range of temperatures for which the silicate network is frozen in
but the lithium ions can still be equilibrated. The lithium dynamics is studied
via the analysis of different correlation functions. The activation energy for
the lithium mobility agrees very well with experimental data. The correlation
of the dynamics of adjacent ions is weak. At low temperatures the dynamics can
be separated into local vibrational dynamics and hopping events between
adjacent lithium sites. The derivative of the mean square displacement displays
several characteristic time regimes. They can be directly mapped onto
respective frequency regimes for the conductivity. In particular it is possible
to identify time regimes dominated by localized dynamics and long-range
dynamics, respectively. The question of time-temperature superposition is
discussed for the mean square displacement and the incoherent scattering
function.
