`dftd3`

¶

This keyword is used to add the DFT-D3 dispersion correction to NEP. It has no effect when any other potential is used. For theoretical background on DFT-D3, see [Grimme2010] and [Grimme2011].

## Syntax¶

dftd3 <functional> <potential_cutoff> <coordination_number_cutoff>

where `functional`

is the exchange-correlation functional used in generating the reference data for training the NEP model, `potential_cutoff`

is the cutoff radius (in units of Angstrom) for the D3 potential, and `coordination_number_cutoff`

is the cutoff radius (in units of Angstrom) for calculating the coordination numbers.

This keyword can be put anywhere in the `run.in`

input file.

We have only implemented the Becke-Johnson (BJ) damping, and a full list of supported functionals can be found from the following link: https://www.chemiebn.uni-bonn.de/pctc/mulliken-center/software/dft-d3/functionalsbj

## Example¶

```
dftd3 pbe 12 6
```

This will add the DFT-D3 dispersion correction to NEP with the PBE functional and a cutoff radius of 12 Angstrom for the D3 potential and a cutoff radius of 6 Angstrom for the coordination number.

## Tips¶

It usually requires to test the convergence with respect to the cutoff radii, and a balance between accuracy and efficiency must be achieved.

The user is responsible for not double counting the dispersion correction, i.e., it is not a good idea to add the DFT-D3 correction to a NEP model that has been trained against a dataset containing dispersion correction (no matter what flavor it is).