Projected CAP/SAC-CI method with smooth Voronoi potential for calculating resonance states.

The complex absorbing potential (CAP)/symmetry-adapted cluster-configuration interaction (SAC-CI) method has been combined with a smooth Voronoi potential, which was recently introduced in the extrapolation procedure, to locate π* resonance states of small- to medium-size molecules. Here, the projected CAP/SAC-CI method is combined with this potential and used to calculate the double-bond and heteroaromatic π* resonances of acetaldehyde, butadiene, glyoxal, pyridine, pyrazine, and furan. As observed in the pilot applications, the corrected η-trajectories provide a stable resonance energy and width or lifetime regardless of the size parameter (rcut ) of the smooth Voronoi potential. However, in general, the stabilization behavior of the trajectories is clearer for larger rcut values, which implies that the interaction of the CAP with the valence electrons is more advantageously addressed by a larger "cavity" size.