International Journal of Molecular Sciences, Vol.3, No.5, 522-549, 2002
Alternative Multi-reference State-specific Coupled Cluster Wave Functions
An analysis of alternative expressions of the state-specific (SS) multi-reference (MR) coupled cluster (CC) wave functions is presented. The approach utilizes the CASSCF (complete active space self consistent field) wave function as the reference. It is designed specifically for calculating excited electronic states. The cluster structure of the CC wave operator and the origin(s) for the cluster expansion(s) are the key features of the development. Test calculations reveal some interesting features of the SMRCC approaches.
Keywords:electronic wave function;coupled cluster method;multi-reference;state-selective approach;spin-adapted wave function;electronic excited states