From Intermolecular Interaction Energies and Observable Shifts to Component Contributions and Back Again: A Tale of Variational Energy Decomposition Analysis

Abstract

Quantum chemistry in the form of density functional theory (DFT) calculations is a powerful numerical experiment for predicting intermolecular interaction energies. However, no chemical insight is gained in this way beyond predictions of observables. Energy decomposition analysis (EDA) can quantitatively bridge this gap by providing values for the chemical drivers of the interactions, such as permanent electrostatics, Pauli repulsion, dispersion, and charge transfer. These energetic contributions are identified by performing DFT calculations with constraints that disable components of the interaction. This review describes the second-generation version of the absolutely localized molecular orbital EDA (ALMO-EDA-II). The effects of different physical contributions on changes in observables such as structure and vibrational frequencies upon complex formation are characterized via the adiabatic EDA. Example applications include red- versus blue-shifting hydrogen bonds; the bonding and frequency shifts of CO, N2, and BF bound to a [Ru(II)(NH3)5]2 + moiety; and the nature of the strongly bound complexes between pyridine and the benzene and naphthalene radical cations. Additionally, the use of ALMO-EDA-II to benchmark and guide the development of advanced force fields for molecular simulation is illustrated with the recent, very promising, MB-UCB potential. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Oxidation State Localized Orbitals: A Method for Assigning Oxidation States Using Optimally Fragment-Localized Orbitals and a Fragment Orbital Localization Index

“…Indeed there has been much development of specialized methods that aim to specifically localize orbitals onto fragments [36][37][38][39][40][41][42][43][44] rather than maximizing a global measure of localization. Such methods have considerable value in energy decomposition analysis of intermolecular interactions, 45,46 as well as for fragment methods and embedding. 41,44,47 In our context there is a di↵erent need for fragment localization.…”

Dissociation of HCl in water nanoclusters: an energy decomposition analysis perspective

“…43,[52][53][54][55] A general review is also available. 56 The binding energy of fragments, ∆E bind , consists of the purely electronic interaction energy, ∆E int , and the energy needed to deform the isolated fragments to the geometry they adopt in the complex, ∆E gd . In its original formulation, 43 the ALMO-EDA scheme partitions the interaction energy ∆E int into components associated with frozen interaction (frz), polarization (pol), and charge-transfer (ct):…”

Consistent inclusion of continuum solvation in energy decomposition analysis: theory and application to molecular CO2 reduction catalysts

“…Energy decomposition analysis (EDA) 25–29 is a powerful tool that facilitates one's understanding of intermolecular interactions by quantifying the relative importance of various physically motivated components, such as permanent electrostatics, polarization, dispersion, etc. While there are many perturbative or variational EDA schemes available, these developments have been focusing on intermolecular interactions in vacuum.…”

“…In this paper, we integrate SCRF implicit solvent models with energy decomposition analysis of DFT calculations based on absolutely localized molecular orbitals (ALMO-EDA), whose gas-phase version was previously developed by some of us. 29,45–47 For brevity, we denote this new extension of the ALMO-EDA for studying non-covalent interactions in solution as “ALMO-EDA(solv)” throughout this paper. The second-generation ALMO-EDA method 46,47 partitions the total interaction energy (Δ E INT ) into contributions from permanent electrostatics (ELEC), Pauli repulsion (PAULI), dispersion (DISP), polarization (POL), and charge transfer (CT):Δ E INT = Δ E ELEC + Δ E PAULI + Δ E DISP + Δ E POL + Δ E CT where the first three terms constitute the frozen interaction energy (Δ E FRZ ).…”