ELECTRONIC-STRUCTURE OF RANDOM AL0.5GA0.5AS ALLOYS - TEST OF THE SPECIAL-QUASIRANDOM-STRUCTURES DESCRIPTION

The spectral properties of an sp3s* tight-binding Hamiltonian for a random, unrelaxed Al0.5Ga0.5As alloy are calculated using three different techniques: the coherent-potential approximation, the recursion method (as applied to a >2000 atom supercell), and the recently introduced special-quasirandom-structures (SQS) approach. Over a broad range of scattering strengths, the dominant spectral features predicted by the first two techniques are well reproduced by calculations for an SQS with 16 atoms/unit-cell (SQS-8). This suggests that the SQS approach might also be useful in cases where the other methods are difficult to apply, e.g., in first-principles calculations for structurally relaxed alloys. © 1990 The American Physical Society.