Add VASP setting for the dftd4 vdW functional.

[hongyi-zhao]

Feature Requested

VASP has implemented support for dftd4, as stated on VASP wiki.

On the other hand, pymatgen still doesn't support dftd4, as shown here. So, I think it should be better if we can add support for dftd4 in pymatgen.

Proposed Solution

According to the description here, it seems adding the following into https://github.com/materialsproject/pymatgen/blob/master/pymatgen/io/vasp/vdW_parameters.yaml should be enough:

dftd4:
    IVDW: 13

Relevant Information

The related packages, such as this file in the atomate2, should also be updated accordingly.

If there are any omissions or considerations I have overlooked, please feel free to point them out.

Regards, Zhao