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Third‐order quasidegenerate many‐body perturbation theory calculations for valence state correlation energies of the nitrogen and oxygen atoms and their ions
Author(s) -
Sheppard Maurice G.,
Freed Karl F.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560200804
Subject(s) - valence (chemistry) , atomic physics , chemistry , electronic correlation , ion , valence electron , electron , hamiltonian (control theory) , oxygen , nitrogen , perturbation theory (quantum mechanics) , physics , quantum mechanics , organic chemistry , mathematical optimization , mathematics
Third order quasidegenerate many‐body perturbation theory (QDMBPT) is used to calculate all [2 s , 2 p ] valence state correlation energies of nitrogen and oxygen for all numbers of valence electrons, N v . The average deviations from experiment for all energies are 0.31 eV for nitrogen and 0.26 eV for oxygen. Rather than using the conventional QDMBPT treatment in which the N N electron matrix elements of the appropriate effective Hamiltonian ( H H ) are calculated directly, H H is separated into a sum of individual many‐electron operators which are independent of N v . The effective many‐electron integrals for a given species are therefore calculated once and then used to construct H H for all values of N v . This two step procedure has the special virtue of yielding all valence state correlation energies for all valence ions from a single calculation.