Band structure calculation of semiconductors and alloys with diamond and zincblende-crystal lattices

A local pseudopotential with six parameters (three for the symmetric and three for the antisymmetric part) was fitted to recent experimental data from photoemission and modulated optical properties of elemental and compound (II–VI) semiconductors, using a basis of 59 plane waves, symmetrized along the (100) and (111) axes ink-space. An extensive critical analysis of current assignments for several transitions is developed. The pseudopotential form factors found are used to calculate variations of direct gaps with composition in the virtual crystal approximation. These results disagree partially with experiment, indicating the inadequacy of the local-pseudopotential interpolation model of alloys, except in cases where the important gaps are dominated by form factors which are very similar in both components and where the gap variation with mole fraction can be proved to be approximately linear in consequence.