Symmetry-adapted cluster–configuration interaction method applied to high-spin multiplicity

The SAC–CI (symmetry-adapted cluster–configuration interaction) method is extended to high-spin multiplicity and applied to the quartet, quintet, sixtet, and septet states of N2, N2+, OH, and m-phenylenebis(methylene) (m-PBM) molecules. The results show good agreement with those of the full-CI reference calculations, though the dimensions of the calculations are much smaller than those of the full-CI method. The smallness of the calculational efforts and the excellent agreement with the full-CI results assure that the SAC–CI method is useful and accurate not only for singlet, doublet, and triplet states but also for high-spin multiplet states.