Similarity transformed equation-of-motion coupled-cluster theory: Details, examples, and comparisons

The similarity transformed equation-of-motion coupled-cluster (STEOM-CC) method is presented in full detail. Comparisons are made with the Pock space coupled-cluster (FSCC) method and the equation-of-motion coupled-cluster (EOM-CC) scheme. The role of implicit triple excitations and, relatedly, charge transfer separability in STEOM is discussed. The dependence on the choice of active space in STEOM is addressed and criteria for the selection of the active space are given. The evaluation of properties within STEOM is outlined and a large number of illustrative examples of STEOM is presented. (C) 1997 American Institute of Physics. [S0021-9606(97)02841-9].