Using semirelativistic norm-conserving pseudopotentials and a mixed Gaussian–plane-wave basis set, we have performed very accurate self-consistent calculations of the energy bands and cohesive energies of GaAs, AlAs, and the (GaAs${)}_1$(AlAs${)}_1$(001) superlattice. To facilitate comparisons and ensure equal errors in the cohesive energies, all calculations were performed using the superlattice unit cell. Unlike other calculations, our calculated superlattice formation energy is negative (-9.2 meV per unit cell) and unlike other calculations our calculated equilibrium GaAs and AlAs lattice constants are in near perfect agreement with experiment so that no ad hoc strain correction need be added to the superlattice energy.

• Received 19 May 1986

DOI:https://doi.org/10.1103/PhysRevB.34.5280