| Abstract
| - We have extended the evaluation and interpretation of QTAIM (quantum theory of atoms in molecules)localization and delocalization indices λ (LI) and δ (DI) to electronic excited states by studying ground states(at HF and CCSD levels) and excited states (at CIS and EOM-CCSD) of H2CCH2, HC⋮CH, H2CO,H2CS, CO2, CS2, and SO2. These molecules undergo extensive geometrical changes upon the excitation tothe valence adiabatic excited singlet state. The importance of Coulomb correlation effects was demonstratedby comparing the LIs and DIs at none-correlated levels (HF and CIS) and those at correlated levels (CCSDand EOM-CCSD). In interpreting the changes in the magnitudes of the LIs and DIs, we made use of simplemolecular orbital and Walsh-diagram analyses. Coulomb correlation is important in determining the magnitudeof the LIs and DIs and obtaining geometries that are close to experiment.
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