Comparison of Density-Functional Theory Dispersion Corrections for the DES15K Database

While density-functional theory (DFT) remains one of
the most widely
used tools in computational chemistry, most functionals fail to properly
account for the effects of London dispersion. Hence, there are many
popular post-self-consistent methods to add a dispersion correction
to the DFT energy. Until now, the most popular methods have never
been compared on equal footing due to not being implemented in the
same electronic structure packages. In this work, we performed a large-scale
benchmarking study, directly comparing the accuracy of the exchange-hole
dipole moment (XDM), D3BJ, D4, TS, MBD, and MBD-NL dispersion models
when applied to the recent DES15K database of nearly 15,000 molecular
complexes at both expanded and compressed geometries. Our study showed
similarly good performance for all dispersion methods (except TS)
when applied to neutral complexes. However, they all performed worse
for ionic complexes, particularly those involving dications of alkaline
earth metals, due to systematic overbinding by the base PBE0 density
functional. Investigation of the largest outliers also revealed that
only the MBD and MBD-NL methods demonstrate surprising errors for
complexes involving alkali metal cations at compressed geometries
where they tended to significantly overbind. As we would expect minimal
dispersion binding for such complexes, we further investigated the
origins of these errors for the potential energy curve of a model
cation–π complex. Overall, there is little choice between
the XDM, D3BJ, D4, MBD, and MBD-NL dispersion methods for most systems.
However, the MBD-based methods are not recommended for complexes involving
organic species and alkali or alkaline earth metal cations, for example
when modeling Li+ intercalation into graphite.