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

Abstract

AbstractWe 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 E2 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 E1 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. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003