| Abstract: | We describe a simple expansion of the Krylov type for the estimation of the electronic correlation energy of the ground state of closed-shell systems and show its relationship with Brillouin–Wigner perturbation theory. We demonstrate the Brillouin–Wigner perturbation theory can be quickly solved in a noniterative fashion. Examples are presented using the intermediate neglect of the differential overlap model Hamiltonian (INDO /1), which indicates that this scheme captures well over 95% of the configuration interaction over double excitations method (CID ) in a fraction of the computational effort. © 1993 John Wiley & Sons, Inc. |
