Revised Damping Parameters for the D3 Dispersion Correction to Density Functional Theory

Since
the original fitting of Grimme’s DFT-D3 damping parameters,
the number and quality of benchmark interaction energies has increased
significantly. Here, conventional benchmark sets, which focus on minimum-orientation
radial curves at the expense of angular diversity, are augmented by
new databases such as side chain–side chain interactions (SSI),
which are composed of interactions gleaned from crystal data and contain
no such minima-focused bias. Moreover, some existing databases such
as S22×5 are extended to shorter intermolecular separations.
This improved DFT-D3 training set provides a balanced description
of distances, covers the entire range of interaction types, and at
1526 data points is far larger than the original training set of 130.
The results are validated against a new collection of 6773 data points
and demonstrate that the effect of refitting the damping parameters
ranges from no change in accuracy (LC-ωPBE-D3) to an almost
2-fold decrease in average error (PBE-D3).