Energy decompositions according to physical space partitioning schemes: Treatments of the density cumulant

Abstract

Articles you may be interested inA new ab initio potential energy surface for the collisional excitation of HCN by para-and ortho-H2 J. Chem. Phys. 139, 224301 (2013) 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 ͑2005͔͒ 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.

Topology of the Electron Density in Open-Shell Systems

“…The contributions of the paired and spin exchange density parts of the particle density, delocalized over the internuclear region, exhibit a high concentration that reflects the local view of the nonlocal formalisms to bonding between atoms. 12 The cumulant density (Figure 2f) shows the typical shell structure found for closed-shell compounds with nuclear concentrations (oblique line), spherical valence shell concentrations, and depletion at the bond midpoint (vertical line); 8,9 its slight delocalization over the bonding internuclear region confirms its localized character 13,35 and a typical behavior of systems containing B atoms. 10 Figures 3 and 4 are dedicated to show the L(r) contour maps for the CH 3 doublet state 2 A 2 ′′ in the molecular plane and in a perpendicular plane to the molecule containing a CH bond, respectively.…”

Natural bond orbital‐based energy density analysis for correlated methods: Second‐order Møller–Plesset perturbation and coupled‐cluster singles and doubles

“…Our group has developed energy partitioning schemes based on atomic orbital 26 and partitioning function 27 for correlated methods. The similar partitioning schemes have been proposed by Sinanoğlu and other researchers 28–38. In this article, we propose a new energy partitioning scheme for the coupled‐cluster singles and doubles (CCSD) 50 and second‐order Møller–Plesset perturbation (MP2) 51 theories by using information of natural bond orbitals (NBOs), which have been advocated and calibrated by Weinhold and coworkers 52–54.…”

“…As for the populations, bond order 1 and overlap population 2 are capable of acquiring information about bonds, even though they are sensitive to the choice of a basis set. As for energy, several groups have recently proposed simple energy partitioning schemes 3–38, which allow us to investigate electron behaviors by splitting total energies into atomic and/or bonding contributions. Those energy partitioning schemes for ab initio methods such as Hartree–Fock (HF) and density functional theory (DFT) have been applied to scientifically intriguing phenomena 39–49.…”

Pairing and unpairing electron densities in organic systems: Two-electron three center through space and through bonds interactions

“…(1)) applied to the partition of the energy and the consequent definition of the atomic and bond energy. 28,46…”