A CAS-DFT study of fundamental degenerate and nearly degenerate systems

Abstract

Abstract We present simple CAS-DFT approaches for degenerate and nearly degenerate systems. In this method, we do not employ any auxiliary variables, but employ the effective CASCI-DFT and CASSCF-DFT equations for the ground and excited states. Simple applications for fundamental systems such as atomic multiplet states (C, N+n , and O+n ), the transition metal complex V(III)L6 (L = H2O and CO) and the Cu(II) acetate dimer Cu(II)2(Ac)4(H2O)2 are presented. The results are discussed from the viewpoint of the shapes of the potential curves of several nearly degenerate spin states, the theory of molecular magnetism and the reliability of the CAS space employed. The computational results are fully compatible with the experimental results available, and also with those of ligand field theory. Keywords: CAS-DFTDegenerate systemsMolecular magnetism Acknowledgement This work was supported by the CREST project of the Japan Science and Technology Agency (JST).