Excitation energies from time-dependent density functional theory using exact and approximate potentials

Abstract

The role of the exchange–correlation potential and the exchange–correlation kernel in the calculation of excitation energies from time-dependent density functional theory is studied. Excitation energies of the helium and beryllium atoms are calculated, both from the exact Kohn–Sham ground-state potential and from two orbital-dependent approximations. These are exact exchange and self-interaction corrected local density approximation (SIC-LDA), both calculated using Krieger–Li–Iafrate approximation. For the exchange–correlation kernels, three adiabatic approximations were tested: the local density approximation, exact exchange, and SIC-LDA. The choice of the ground-state exchange–correlation potential has the largest impact on the absolute position of most excitation energies. In particular, orbital-dependent approximate potentials result in a uniform shift of the transition energies to the Rydberg states. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 534–554, 2000