Empirical Dispersion Correction for DFT Calculations

Based on an idea that has earlier been proposed for Hartree-Fock calculations[75,76], a general empirical dispersion correction has been proposed by Stefan Grimme for density functional calculations [77]. A modified version of the approach with extension to more elements and more functionals has been published in ref. [78]. The most recent implementation [79] is less empirical, i.e. the most important parameters are computed by first principles, and it provides a consistent description across the whole periodic system.

The first version (DFT-D1) can be invoked by the keyword `$olddisp` in
the `control` file.
The second version (DFT-D2) is used if the keyword `$disp` is found.
For the usage of DFT-D3 just add keyword `$disp3` to the `control` file. Only one of the three keywords is expected to be present.

If DFT-D3 is used, the total energy is given by

E_{DFT-D3} = E_{KS-DFT} - E_{disp} |
(6.9) |

where

with the dominating two-body term

The first sum runs over all atom pair, *C*_{n}^{AB} denotes the *n*th-order dispersion
coefficient for atom pair *AB*, *r*_{AB} is their interatomic distance, and *f*_{d, n}
is a damping function.

Please have look at http://toc.uni-muenster.de/DFTD3 for more detailed information.