Extended Koopmans' theorem at the second-order perturbation theory

Détails bibliographiques
Publié dans:	Journal of computational chemistry. - 1984. - 41(2020), 12 vom: 05. Mai, Seite 1165-1174
Auteur principal:	Gu, Yonghao (Auteur)
Autres auteurs:	Xu, Xin
Format:	Article en ligne
Langue:	English
Publié:	2020
Accès à la collection:	Journal of computational chemistry
Sujets:	Journal Article Koopmans' theorem extend Koopmans' theorem ionization potential relaxed density matrix second-order Møller−Plesset perturbation theory

Description
Résumé:	© 2020 Wiley Periodicals, Inc. The extended Koopmans' theorem (EKT), when combined with the second-order Møller-Plesset (MP2) perturbation theory through the relaxed density matrix approach [J. Cioslowski, P. Piskorz, and G. Liu, J. Chem. Phys. 1997, 107, 6,804], provides a straightforward way to calculate the ionization potentials (IPs) as an one electron quantity. However, such an EKT-MP2 method often suffers from the negative occupation problem, failing to provide the complete IP spectra for a system of interest. Here a small positive number scheme is proposed to cure this problem so as to remove the associated unphysical results. In order to obtain an in-depth physical interpretation of the EKT-MP2 method, we introduce a Koopmans-type quantity, named KT-MP2, based on which the respective contribution from the relaxation and the correlation parts in the EKT-MP2 results are recognized. Furthermore, the close relationship between the EKT-MP2 method and the derivative approach of the MP2 energy with respect to the orbital occupation numbers [N. Q. Su and X. Xu, J. Chem. Theory Comput. 2015, 11, 4,677] is revealed. When these MP2-based methods are applied to a set of atoms and molecules, new insights are gained on the role played by the relaxation and the correlation effects in the electron ionization processes
Description:	Date Revised 31.03.2020 published: Print-Electronic Citation Status PubMed-not-MEDLINE
ISSN:	1096-987X
DOI:	10.1002/jcc.26163