Accurate excitation energies from time-dependent density functional theory: Assessing the PBE0 model

We analyze the performance of a density functional model obtained by combining the Perdew-Burke-Erzenrhof (PBE) generalized gradient functional with a predetermined amount of exact exchange for predicting vertical electronic excitation energies within a time-dependent approach. Four molecules, namely, CO, H2CO, (CH3)(2)CO, and C2H4, have been chosen as benchmark cases. Our results show that this model (PBE0) provides accurate excitations both to valence and Rydberg states. Furthermore, the results are numerically close to those obtained using asymptotically correct exchange-correlation functionals. The performance of the PBE0 model for predicting excitation energies in larger molecules is assessed for benzene, pyridine, and naphthalene. Here, the PBE0 model provides results which are in fairly good agreement with experimental data and of similar quality to those obtained by more sophisticated (and time-consuming) post-Hartree-Fock methods. (C) 1999 American Institute of Physics. [S0021-9606(99)30531-6].