Resonating Broken Symmetry CI Approach for Ion-Radical Systems: Comparison With UHF, Hybrid-DFT, and CASSCF-DFT

摘要

The resonating broken-symmetry configuration interaction (RBS-CI) approach, in which we employ two Spin-Unrestricted Hartree-Fock (UHF) solutions as the basis, is applied for the ion-radical systems. The RBS-CI results are compared with those of UHF, various hybrid density functional theory (DFT), and CASSCF-DFT. The hybrid DFT leads to the spurious delocalized state as is well known, whereas the UHF to the localized state. The CASSCF-DFT results show that the excess electron localized, missing the spatial symmetry of the systems. On the other hand, the Res-HF Cl results satisfy the spatial symmetry as well as the Perdew, Parr, Levy, and Balduz's relation implying that this method is so-called many-electron self-interaction free (ME-SIF), whereas all other method,; are not ME-SIF. These results suggest that the RBS-CI approach will become not only a powerful ab initio approach, but also a guideline to construct a new exchange-correlation functional of hybrid-DFT, for the ion-radical systems. (C) 2008 Wilev Periodicals, Inc. Int J Quantum Chem 108: 2960-2977, 2008