[ase-users] DFTD3 calculator which interfaces with the dftd3 reference implementation

[Eric Hermes]

Hello,

Some may remember that I wrote a third-party implementation of Grimme's
D3 dispersion correction method and attempted to have it merged into
ASE. Unfortunately, my code relied on a Fortran module to do the bulk
of the work due to the intensity of the three-body dispersion
correction. This is still available at https://gitlab.com/ehermes/ased3
 as a separate calculator, but unfortunately it is still quite buggy
(it can only be build with the Intel Fortran compiler currently...).

In order to have something that can be used by all users of ASE, I have
decided to write a FileIOCalculator for Grimme's dftd3 reference
implementation. The merge request for this calculator is available
here: https://gitlab.com/ase/ase/merge_requests/490. I believe this is
ready to be merged, but I would like for it to get some eyeballs on it
to ensure that I have not missed anything crucial.

This calculator can be used by itself or in conjunction with any
calculator that adheres to the ase.calculators.calculator.Calculator
interface. Note that the reference implementation for dftd3 is not
parallel, so if your system is very large and the DFT calculator is
running on many CPUs, the dispersion correction may be rate limiting --
especially if you enable three-body corrections.

Let me know if you have any questions or concerns about this merge
request. Otherwise, I plan on merging it myself by the end of the week.

Eric Hermes