Theoretical approaches to the electronic structure of disordered solids

A short review is presented on a theoretical numerical approach to the calc ulation of the electronic structure of disordered and amorphous solids. A c hemically specific approach is thereby advocated. A new procedure to fit in a tight-binding method the band structure of complex solids is introduced. The electronic structure of different defect models of a-Si and a-Si:H is described. Then the interplay of disorder and electron-electron interaction s in the disordered cubic tungsten bronzes, NaxWO3, is addressed which lead s to a pseudogap at the Fermi level. This work results in an understanding of the metal-insulator transition for finite doping degree. (C) 1999 Elsevi er Science B.V. All rights reserved.