Electron Correlation: Nature's Weird and Wonderful Chemical Glue

Abstract

It can be argued that electron correlation, as a concept, deserves the same prominence in general chemistry as molecular orbital theory. We show how it acts as Nature's "chemical glue" at both the molecular and supramolecular levels. Electron correlation can be presented in a general chemistry course in an at least somewhat intuitive manner. We also propose a simple classification of correlation effects based on their length scales and the size of the orbital gap (relative to the two-electron integrals). In the discussion, we also show how DFT can shed light on wavefunction theory, and conversely. We discuss two types of "honorary valence orbitals", one related to small core-valence gaps, the other to the ability of empty 3d orbitals in 2nd row elements to act as backbonding acceptors. Finally, we show why the pursuit of absolute total energies for their own sake becomes a sterile exercise, and why atomization energies are a more realistic "fix point".

Israel Journal of Chemistry, Early View (2022) [Perspective Article for special issue "Rosarium Philosophorum" dedicated to computational chemistry] (CC-BY Open Access)

References in corpus (6)

• W4 theory for computational thermochemistry: in pursuit of confident sub-kJ/mol predictions
• W3 theory: robust computational thermochemistry in the kJ/mol accuracy range
• Basis set convergence of post-CCSD contributions to molecular atomization energies
• Separation of Dynamic and Nondynamic Correlation
• Heats of formation of perchloric acid, HClO${}_4$, and perchloric anhydride, Cl${}_2$O${}_7$. Probing the limits of W1 and W2 theory
• Anharmonic force fields of perchloric acid, HClO${}_4$, and perchloric anhydride, Cl${}_2$O${}_7$. An extreme case of inner polarization

Cited by in corpus (5)

• Measuring Electron Correlation. The Impact of Symmetry and Orbital Transformations
• W4$\Lambda$: leveraging $\Lambda$ coupled cluster for accurate computational thermochemistry approaches
• MP2-F12 basis set convergence near the complete basis set limit: are $h$ functions sufficient?
• Computing Electronic Correlation Energies using Linear Depth Quantum Circuits
• The importance of tight $f$ basis functions for heavy p-block oxides and halides: a parallel with tight $d$ functions in the second row