Ground-state electronic and cohesive properties of the pure compounds GaAs and AlAs and of the (GaAs${)}_1$(AlAs${)}_1$ (001) superlattice are investigated using a highly precise local-density all-electron total-energy band-structure approach—the self-consistent full-potential linearized augmented-plane-wave (FLAPW) band method—to obtain the energy bands, density of states, and total energies. The effects of Ga 3d states, spin-orbit interactions, and pressure on the energy gap are analyzed quantitatively. The energy gap of the (1×1) superlattice is found to be direct. The instability of the (1×1) superlattice relative to the constituent pure compounds at T=0 is determined from total-energy differences to be 13.5 meV.

• Received 4 November 1987

DOI:https://doi.org/10.1103/PhysRevB.38.1970