Complete-active-space extended Koopmans theorem method.

Davidson, Ernest R; Ortiz, Joseph Vincent; Staroverov, Viktor N

Davidson, Ernest R; Ortiz, Joseph Vincent; Staroverov, Viktor N.

Afiliación

Davidson ER; Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA.
Ortiz JV; Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849-5312, USA.
Staroverov VN; Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada.

J Chem Phys ; 155(5): 051102, 2021 Aug 07.

Article en En | MEDLINE | ID: mdl-34364362

RESUMEN

The complete-active-space (CAS) extended Koopmans theorem (EKT) method is defined as a special case of the EKT in which the reference state is a CAS configuration interaction (CI) expansion and the electron removal operator acts only on the active orbitals. With these restrictions, the EKT is equivalent to the CI procedure involving all hole-state configurations derived from the active space of the reference wavefunction and has properties analogous to those of the original Koopmans theorem. The equivalence is used to demonstrate in a transparent manner that the first ionization energy predicted by the EKT is in general not exact, i.e., not equal to the difference between the full CI energies of the neutral and the ion, but can approach the full CI result with arbitrary precision even within a finite basis set. The findings also reconcile various statements about the EKT found in the literature.

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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Tipo de estudio: Prognostic_studies Idioma: En Revista: J Chem Phys Año: 2021 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos

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