Abstract
We present the first computer simulations of the Hall effect for a realistic model of a solid, namely amorphous silicon, and succeed in verifying the anomalous change in sign of the Hall coefficient as the Fermi energy is moved from the valence band to the conduction band in accordance with the observations of LeComber, Jones and Spear in 1977. A model for this behaviour is proposed based on previous computations of the spectral function and a theory of gap formation.