Energy decomposition analysis

5 years ago

Energy decomposition analysis

Gernot Frenking, Moritz Hopffgarten, Diego M. Andrada, Lili Zhao

The energy decomposition analysis (EDA) is a powerful method for a quantitative interpretation of chemical bonds in terms of three major components. The instantaneous interaction energy ΔEint between two fragments A and B in a molecule A–B is partitioned in three terms, namely (1) the quasiclassical electrostatic interaction ΔEelstat between the fragments; (2) the repulsive exchange (Pauli) interaction ΔEPauli between electrons of the two fragments having the same spin, and (3) the orbital (covalent) interaction ΔEorb which comes from the orbital relaxation and the orbital mixing between the fragments. The latter term can be decomposed into contributions of orbitals with different symmetry which makes it possible to distinguish between σ, π, and δ bonding. After a short introduction into the theoretical background of the EDA we present illustrative examples of main group and transition metal chemistry. The results show that the EDA terms can be interpreted in chemically meaningful way thus providing a bridge between quantum chemical calculations and heuristic bonding models of traditional chemistry. The extension to the EDA–Natural Orbitals for Chemical Valence (NOCV) method makes it possible to breakdown the orbital term ΔEorb into pairwise orbital contributions of the interacting fragments. The method provides a bridge between MO correlations diagrams and pairwise orbital interactions, which have been shown in the past to correlate with the structures and reactivities of molecules. There is a link between frontier orbital theory and orbital symmetry rules and the quantitative charge- and energy partitioning scheme that is provided by the EDA–NOCV terms. The strength of the pairwise orbital interactions can quantitatively be estimated and the associated change in the electronic structure can be visualized by plotting the deformation densities. For further resources related to this article, please visit the WIREs website. First column: Plot of the deformation densities Δρ1–4 with associated stabilization energies ΔE1–4 of the four most important orbital interactions in B2(NHCMe)2. The color code for the charge flow is redlight blue. Third and fourth column: Plot of the interacting donor and acceptor orbitals and calculated eigenvalues ε of (NHCMe)2 and (1Σg+) B2. Second column: Resulting MOs of the complex B2(NHCMe)2.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/wcms.1345