Optical properties and electronic structures of semiconductors with screened-exchange LDA

Results of first-principles calculations of the optical properties and elec tronic structure, determined by employing the screened-exchange LDA method to obtain accurate electronic structures as well as self-consistent eigenfu nctions, are presented for some cubic semiconductors (Si, Ge, InSb, and GaA s). As implemented in the full-potential linearized augmented-plane-wave me thod, this approach does not require any adjustable parameters to calculate optical properties. The inadequacy of using the transverse expression of t he dielectric function (involving ep matrix elements) is shown numerically for the optical spectra and dielectric constants even when the renormalizat ion factor associated with the LDA eigenvalues is included. This is because the nonlocality of the Hamiltonian and the difference of the self-consiste nt eigenfunctions from the LDA ones are not negligible. In contrast, the op tical properties evaluated using the longitudinal expression (with e(iq.r) matrix elements) yield excellent agreement with experiment considering the neglect of lifetime, local-field, and excitonic effects. [S0163-1829(99)017 08-7].