SIMILARITY TRANSFORMED EQUATION-OF-MOTION COUPLED-CLUSTER STUDY OF IONIZED, ELECTRON ATTACHED, AND EXCITED-STATES OF FREE-BASE PORPHIN

The newly developed similarity transformed equation-of-motion coupled- cluster (STEOM-CC) method and its perturbative analog (STEOM-PT) are a pplied to obtain ionization potentials, electron affinities and single t and triplet excitation energies of free base porphin. STEOM-CC resul ts are found to agree nicely with the available experimental data. Gro und-state correlation is not described adequately in lowest order of p erturbation theory, although STEOM-PT results qualitatively agree with the infinite order STEOM-CC results. The STEOM computational strategy is operationally like CI singles for excited states, which leads to e xceptional efficiency. (C) 1997 American Institute of Physics.