  The existence of conduction channels in lithium silicate (Li_2O)(SiO_2) is
investigated. Regions of the system where many different ions pass by form
channels and are thus spatially correlated. For a closer analysis the
properties of the individual ionic sites are elucidated. The mobility of ions
in single sites is found to depend strongly on the number of bridging oxygens
in the coordination shell. The channels are not reflected in the network
structure as obtained from the distribution of the bridging oxygens. Spatial
correlations similar to those found in the silicate also emerge from studying
the dynamics of particles in a simple random lattice model. This supports the
suggestion that the observed spatial correlations can be viewed in analogy to
the emergence of percolation paths.
