The reaction pathway for the rupture of the carbon-carbon double bond of C F has been calculated with ab initio methods at the CASSCF(8,8)+NEVPT2/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels and with density functional theory using M06-L and M06-2X functionals in conjunction with aug-cc-pVTZ basis sets. The calculations suggest that the bond dissociation pathway proceeds by a nonlinear reaction course without an activation barrier yielding the CF fragments in the ( A ) ground state. A bonding analysis indicates that there is a continuous change in the electronic structure of the CF fragments during the elongation of the C-C distance from a ( B ) excited state at the equilibrium geometry of C F to the ( A ) ground state. EDA-NOCV calculations suggest that the carbon-carbon interactions in C F at equilibrium distance and longer C-C values up to ≈1.60 Å are best described in terms of electron-sharing bonding between the CF fragments in the ( B ) excited state. At longer distances, the situation changes toward dative bonding between CF fragments in the ( A ) ground state.

The suggested method is illustrated with several molecules together with some of the most popular local and hybrid DFT functionals. Overall, we anticipate that the approach put forward in this work will prove useful in getting further insights of phenomena in chemistry which are properly described with DFT .

The increasing availability of real‐space interaction energies between quantum atoms or fragments that provide a chemically intuitive decomposition of intrinsic bond energies into electrostatic and covalent terms [see, for instance, Chem. Eur. J. 2018, 24, 9101] provides evidence for differences between the physicist's concept of interaction and the chemist's concept of a bond. Herein, it is argued that, for the former, all types of interactions are treated equally, whereas, for the latter, only the covalent short‐range interactions have actually been used to build intuition about chemical graphs and chemical bonds. This has led to the bonding role of long‐range Coulombic terms in molecular chemistry being overlooked. Simultaneously, blind consideration of electrostatic terms in chemical bonding parlance may lead to confusion. The relationship between these concepts is examined herein, and some notes of caution on how to merge them are proposed.

In this contribution we introduce the concept of bond order density (BOD) based on previous work on natural adaptive orbitals. We show that BODs may be used to visualize both the global spatial distribution of the covalent bond order as well as its eigen-components, which we call bond(ing) channels. BODs can be equally computed at correlated and non-correlated levels of theory, and in ground or excited states, thus offering an appealing description of bondforming, bond-breaking, and bond-evolution processes. We show the power of the approach by examining a number of homo-and hetero-diatomics, including the controversial existence of a fourth bonding component in dicarbon, by analyzing a few interesting bonding situations in polyatomics and chemical transformations, and by exemplifying exotic bonding behaviors in simple excited electronic states.

We put together equation of motion coupled cluster theory and the interacting quantum atoms electronic energy partition to determine how an absorbed photon changes atomic energies as well as covalent and noncovalent interactions within a molecule or molecular cluster.