Weaire-Thorpe

Figure 8.03. (top) The density of states from rigorous band structure calculations (the zero of energy marks the Fermi level), (bottom) the density of states calculated using Weaire-Thorpe Hamiltonian (After Weaire et al., 1972). 

These results were most clearly stated by Weaire and Thorpe (Weaire 1971, Thorpe and Weaire 1971), who described the bonding by a tight binding Hamiltonian of the form... 

D. Weaire, M. F. Thorpe, R. Alben, and S. Goldstein, in Eleventh International Conference on the Physics of Semiconductors, p. 470, Polish Scientific, Warsaw, 1972. 

Tight binding methods were developed for the calculation of the electronic states in amorphous solids by Weaire (1971), Weaire and Thorpe (1971), Thorpe and Weaire (1971a, b), Heine (1971), Thorpe and Weaire (1971a, b) and L. Roth (1972). Their calculations of the band state densities are explicitly based on the consideration of the short-range. Chen... 

Wiech and Zopf (1972) measured the soft X-ray emission spectra of a-Si, Eastman (1972) and Ley et al (1972) UV and X-ray photoemission from a-Si and a-Ge and obtained information about the state densities in the valence band. They observed two bands as predicted by Thorpe and Weaire (1971) instead of the three bands observed in crystals (Figure 4.28). This experimental result agrees with the above mentioned considerations of Joannopoulos and Cohen (1972). 

---