Optical excitations of Si by time-dependent density functional theory based on exact-exchange Kohn-Sham band structure

Abstract

We calculate the imaginary part of the frequency-dependent dielectric function of bulk silicon by applying time-dependent density functional theory (TDDFT) based on the exact-exchange (EXX) Kohn-Sham (KS) band structure and the adiabatic local-density approximation (ALDA) kernel. The position of the E, absorption peak calculated with the EXX band structure at the independent-particle level is in excellent agreement with experiments, which demonstrate the good quality of EXX "KS quasiparticles." The excitonic E-1 peak that is missing at the independent-particle level remains absent if two-particle interaction effects are taken into account within the ALDA to TDDFT, demonstrating the incapability of the ALDA kernel to describe excitonic effects. (C) 2002 Wiley Periodicals, Inc.