  Using our recently developed Chebyshev expansion technique for
finite-temperature dynamical correlation functions we numerically study the AC
conductivity $\sigma(\omega)$ of the Anderson model on large cubic clusters of
up to $100^3$ sites. Extending previous results we focus on the role of the
boundary conditions and check the consistency of the DC limit, $\omega\to 0$,
by comparing with direct conductance calculations based on a Greens function
approach in a Landauer B\"uttiker type setup.
