LINEAR AND NONLINEAR SPECTROSCOPY OF GAAS AND GAP - THEORY VERSUS EXPERIMENT

We have calculated and compared the linear and non-linear optical resp onse of GaAs and Gap bulk within three methods: ab-initio density func tional theory (DFT); local density approximation (LDA)-based pseudopot ential plane wave (PPW); and full-potential linearized augmented plane wave (FLAPW) approaches, together with the empirical tight-binding (E TB) method. Specifically, we have calculated the dielectric function a nd second harmonic generation (SHG) susceptibility over a broad freque ncy range, important conclusions about the applicability of the ETB me thod for the calculation of bulk optical responses have been drawn wit h respect to the higher-order susceptibility. (C) 1998 Elsevier Scienc e S.A.