  We report a simulation of the metal-insulator transition in a model of a
doped semiconductor that treats disorder and interactions on an equal footing.
The model is analyzed using density functional theory. From a multi-fractal
analysis of the Kohn-Sham eigenfunctions, we find $\nu \approx 1.3$ for the
critical exponent of the correlation length. This differs from that of
Anderson's model of localization and suggests that the Coulomb interaction
changes the universality class of the transition.
