  We investigate a single particle on a 3-dimensional, cubic lattice with a
random on-site potential (3D Anderson model). We concretely address the
question whether or not the dynamics of the particle is in full accord with the
diffusion equation. Our approach is based on the time-convolutionless (TCL)
projection operator technique and allows for a detailed investigation of this
question at high temperatures. It turns out that diffusive dynamics is to be
expected for a rather short range of wavelengths, even if the amount of
disorder is tuned to maximize this range. Our results are partially
counterchecked by the numerical solution of the full time-dependent
Schroedinger equation.
