My Community

I'd like to ask about the preparation of POTCAR.
1. We can choose POTCAR as one of regular, soft, or hard. However, it is not clear what's their detailed meaning and in what cases we should use them.
They are concerned with VASP rather than ATK, but if possible, would you give me some information about them?
I suppose that they may be determined depending on the type of the materials such as oxide, metal, organic.

2. Is it right that "regular" can cover all the cases reasonably although the best accuracy may not be obtained depending the system?

Thank you very much for your help in advance.

Best regards,
Young

Pseudopotentials are developed in the way to reproduce properties of solids.
The fitting of the potential is not oriented on different types of materials,
like oxides, metals, etc. but to cover all possible bondings.
Though developed for 3D solids they are applicable also
to slabs, chains, or molecules.