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

摘要

We calculate the imaginary part of the frequency-dependent dielectricfunction of bulk silicon by applying time-dependent density-functional theorybased on the exact-exchange (EXX) Kohn-Sham (KS) band structure and theadiabatic local-density approximation (ALDA) kernel. The position of the E2absorption peak calculated with the EXX band structure at theindependent-particle level is in excellent agreement with experiments, whichdemonstrates the good quality of EXX `KS quasiparticles'. The excitonic E1 peakthat is missing at the independent-particle level remains absent iftwo-particle interaction effects are taken into account within thetime-dependent LDA, demonstrating the incapability of the ALDA kernel todescribe excitonic effects.