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T. Hupp, B. Engels, F. della Sala, A. Görling
Analysis of the Quality of Kohn–Sham Orbitals for Subsequent MRSD-CI Calculations of Excitation Energies
In the present work we study the properties of Kohn–Sham orbitals used in subsequent CI methods for the computation of electronic excitation energies in terms of orbital relaxation, static and dynamical correlation effects. As model systems, we use the water and the ethene molecule. As sets of orbitals, we use orbitals from an effective exact exchange Kohn–Sham method, the localized Hartree–Fock (LHF) method, as well as BLYP and HF orbitals. Our study shows that the use of LHF orbitals leads to negligible static correlation effects and thus facilitates assignments of excitation spectra, but it also shows that the remaining correlation contributions have to be taken into account carefully since error cancellation is only found in some fortitious cases. The comparison of LHF and BLYP orbitals shows that the BLYP orbitals are less suited for the description of the cationic system and as a consequence for the computation of Rydberg states.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 217, 02/2003
Pages: 133