## Erin R. Johnson

*Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, Canada*

Inclusion of a dispersion correction is now the norm when applying density-functional theory (DFT) to systems where non-covalent interactions play an important role. However, there are a wide range of base functionals and dispersion corrections available from which to choose. In this talk, we review how the dispersion energy can be written as an asymptotic series expansion from perturbation theory, which can be added to the self-consistent DFT energy. We then opine on the most desirable requirements to ensure that both the base functional and dispersion correction, individually, are as accurate as possible for non-bonded repulsion and dispersion attraction. The dispersion correction should include higher-order pairwise dispersion terms and electronic many-body effects, while the base functional should be dispersionless, numerically stable, and involve minimal delocalization error. These criteria are essential for avoiding reliance on error cancellation and obtaining correct results from correct physics.

**Keywords:** Density-functional theory; London dispersion; van der Waals complexes; layered materials; molecular crystals

### References

[1] A. Otero de la Roza, L. M. LeBlanc, E. R. Johnson, What is “Many-Body” Dispersion and

Should I Worry About it? Phys. Chem. Chem. Phys. 22, 8266-8276 (2020).

[2] A. J. A. Price, K. R. Bryenton, E. R. Johnson, Requirements for an Accurate Dispersion-

Corrected Density Functional. J. Chem. Phys. 154, 230902 (2021).

[3] K. R. Bryenton, A. A. Adeleke, S. G. Dale, E. R. Johnson, Delocalization Error: The Greatest

Outstanding Challenge in Density-Functional Theory. Wiley Interdiscip. Rev. Comput. Mol. Sci.

13, e1631 (2023).

## Recording:

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