The electronic band structure of GaAs in the SC16 structure along several lines of high symmetry is shown in Figure 4.33. The electronic structure of SC16 GaAs has been published previously[66] but these were calculations based on empirical pseudopotentials where the experimental band gap of the zincblende structure is one of the fitted parameters. It clearly revealed an energy gap in the electronic states of SC16 GaAs of the same magnitude as that found in the zincblende and wurtzite structures. Furthermore, it was suggested that like-species bonds must be present in amorphous heteropolar semiconductors in order to account for the observed reduction in energy gap.
Figure 4.33: The band structure of GaAs in the SC16 structure shown along
several lines of high symmetry in the simple cubic Brillouin zone.
The density of occupied states calculated here exhibits a close
resemblance to that previously reported. However, as is evident from
inspection of the band structure, the valence and conduction bands touch
at the 
point of the Brillouin zone. In view of the well known
inadequacies of density functional theory in determining the electronic
excitation energies in solids this issue cannot be investigated further
using these techniques although partial reduction of the energy gap may
be due to the fact that both the bondlengths in the fully relaxed
structure of SC16 GaAs are smaller than the ideal value found in the
zincblende structure. This situation could have the effect of broadening
the p-like region (approximately -5eV to 0eV) of the density of
states[66].