The ionization operator Ω in the equation-of-motion (EOM) method is written in a form that satisfies the "killer condition" ΩT|Ψ0〉 = 0 for arbitrary multiconfiguration reference states. The resulting equation for ionization potential is equivalent to traditional EOM equation only if the reference state is an exact eigenfunction of the Hamiltonian. The new equation is insensitive to specifying either a simple metric or the "commutator metric", and it represents a Hermitian formulation even for partially optimized wave functions. It is, however, equivalent to a multi-reference CI equation for the ionized state using the extended Koopmans ansatz.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry