### Abstract

The ionization operator Ω in the equation-of-motion (EOM) method is written in a form that satisfies the "killer condition" Ω^{T}|Ψ_{0}〉 = 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.

Original language | English |
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Pages (from-to) | 696-701 |

Number of pages | 6 |

Journal | Physical Chemistry Chemical Physics |

Volume | 3 |

Issue number | 5 |

DOIs | |

Publication status | Published - 2001 |

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### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Atomic and Molecular Physics, and Optics

### Cite this

**On the "killer condition" in the equation-of-motion method : Ionization potentials from multi-reference wave functions.** / Szekeres, Z.; Szabados, A.; Kállay, M.; Surján, P.

Research output: Contribution to journal › Article

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TY - JOUR

T1 - On the "killer condition" in the equation-of-motion method

T2 - Ionization potentials from multi-reference wave functions

AU - Szekeres, Z.

AU - Szabados, A.

AU - Kállay, M.

AU - Surján, P.

PY - 2001

Y1 - 2001

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=0035111149&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035111149&partnerID=8YFLogxK

U2 - 10.1039/b008428j

DO - 10.1039/b008428j

M3 - Article

AN - SCOPUS:0035111149

VL - 3

SP - 696

EP - 701

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 5

ER -