Theoretical approaches to the electronic structure of disordered solids

A short review is presented on a theoretical numerical approach to the calculation of the electronic structure of disordered and amorphous solids. A chemically 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 interactions in the disordered cubic tungsten bronzes, Na_xWO₃, is addressed which leads to a pseudogap at the Fermi level. This work results in an understanding of the metal–insulator transition for finite doping degree.