Interacting Quantum Atoms-A Review

Abstract

The aim of this review is threefold. On the one hand, we intend it to serve as a gentle introduction to the Interacting Quantum Atoms (IQA) methodology for those unfamiliar with it. Second, we expect it to act as an up-to-date reference of recent developments related to IQA. Finally, we want it to highlight a non-exhaustive, yet representative set of showcase examples about how to use IQA to shed light in different chemical problems. To accomplish this, we start by providing a brief context to justify the development of IQA as a real space alternative to other existent energy partition schemes of the non-relativistic energy of molecules. We then introduce a self-contained algebraic derivation of the methodological IQA ecosystem as well as an overview of how these formulations vary with the level of theory employed to obtain the molecular wavefunction upon which the IQA procedure relies. Finally, we review the several applications of IQA as examined by different research groups worldwide to investigate a wide variety of chemical problems.

Keywords: IQA; bonding analysis; energy partition.

Figure 1

Regions of definition of the $D_{l_1{m}_1}^{l_2{m}_2}(r_1,r_2,\mathit{R})$ function.

Figure 2

Biphenyl representations. Schematic (left) and non-overlapping topological atoms bounded by interatomic surfaces (right). Figure from reference [80].

Figure 3

Interacting quantum atoms (IQA) allows for the individual changes in IQA interaction components accompanying the formation of the different hydrogen bonds. Figure from reference [98] shows systems with insaturations and intramolecular HBs (a,b), along with their non-conjugated counterparts (c,d). Figure reproduced by permission of the PCCP Owner Societies.

Figure 4

IQA energy partition of the FB_r ⋯ NH${}_3$ complex. (Top) changes intra-atomic energies (red) and intermolecular interactions (classical and exchange terms in blue and green, respectively). (Bottom) Change in interatomic energies within each fragment upon complex formation. Figure reprinted (adapted) with permission from reference [98]. Copyright 2020 American Chemical Society.

Figure 5

Diagram representing the changes in the strength of the different bonds. The greens arrows represent bond strengthening/forming and while the red ones bond weakening/breaking. Figure taken from Reference [125].

Figure 6

Atomic volume of one of the congested hydrogen atoms in tetra- cyclododecane at a H...H distance of 2.4 Å (top), the equilibrium distance of 1.831 Å (middle), and 0.5 Å (bottom). Figure taken from reference [141].

Figure 7

Flowchart representing the different stages in the training (first four steps) and execution (DL_POLY) of the, detailing the programs involved and summaries of their tasks. Figure taken from reference [147].