Universal valence bands for rocksalt-type compounds and their connection with those of tetrahedral crystals

Using a limited tight-binding basis set, we obtain a universal set of analytical valence bands for rocksalt-type compounds and the rare-gas solids. The bands for each material are obtained by multiplying the universal bands by a scaling factor which is a simple function of the lattice constant and the chemical valence Z of the constituent atoms. Thus, in terms of only two empirically-determined parameters, we get complete valence bands for 51 crystals. We also obtain a universal density-of-states curve in terms of which photoemission spectra may be directly interpreted. Finally, we give a detailed comparison of the valence bands of rocksalt-type compounds with those of the zinc-blende-type compounds and show that the latter are a simple modification of the former. The only fundamental change is the introduction of a splitting at W, and along Z and, which is a manifestation of the tetrahedral forces that are present in the zinc-blende but not the rocksalt crystals. This result complements the well-known fact that the zinc-blende bands are a simple modification of diamond-type bands. © 1975 The American Physical Society.