Abstract
This article is a continuation of our previous paper on schemes of energy decompositions of molecular systems in the real space [D. R. Alcoba et al., J. Chem. Phys. 122, 074102 (2005)] now using correlated state functions. We study, according to physical arguments, the appropriate management of the density cumulant arising from the second-order reduced density matrix at correlated level, whose contributions can be assigned to one-center or to two-center terms in the energy partitioning. Our treatments are applied within two physical space partitioning schemes: the Bader partitioning into atomic basins and the fuzzy atom procedure. The results obtained in selected molecules are analyzed and discussed in detail.
Highlights
The decomposition of the electronic energy of N-electron systems into contributions which can be associated with one, two, or more atom components has received significant attention from many authors recently.[1,2,3,4,5,6,7,8,9,10,11,12] This interest arises from the possibility of determining satisfactorily the strength of the chemical bondings between the atoms which compose a given molecule, atomic group, cluster, etc
As a consequence of the physical meaning of the cu- tables collect results arising from the SCF approximation and mulant describing effectively unpaired electrons, which do not contribute to bondings,[20] its matrix elements ⌳ijkl should be assigned to the one-center components. From this point of view, the elements ⌳ijkl will only contribute to one-center energies; this treatment of the density cumulant will be called from the two-center and one-center models of treatment of the density cumulantcalculated within the CISD approximation
The results reported in Table IIpartitioning of the physical space according to the fuzzy atom pictureshow a similar trend, the values ECCin the C2H6, C2H4, and C2H2 systemsturn out to be higherin all the casesthan in the AIM picture
Summary
The decomposition of the electronic energy of N-electron systems into contributions which can be associated with one, two, or more atom components has received significant attention from many authors recently.[1,2,3,4,5,6,7,8,9,10,11,12] This interest arises from the possibility of determining satisfactorily the strength of the chemical bondings between the atoms which compose a given molecule, atomic group, cluster, etc. These elements are assigned to the two-center terms while in another treatment, according to physical reasons,[20] they are managed as possessing one-center character. Both treatments are developed within the AIM theory and within the fuzzy atom approach.
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