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Convergence with the optB88vdW functional

Posted: Sun Jun 21, 2015 9:50 pm
by hipertrofia
I am doing calculations with the van der Waals corrected optB88vdW functional. I am trying to reproduce the graphene - Ni(111) interaction from Phys. Rev. B 84, 201401(R) (http://journals.aps.org/prb/abstract/10 ... .84.201401). It seems to be working, however the electronic SCF cycle does not seem to be able to converge to the required precision. I have in my INCAR an EDIFF = 1.e-5 eV requirement for a 32 C graphene interacting with a 64 Ni slab (4 layers). VASP basically manages to converge to perhaps one order of magnitude less accurate energies and then stays there until the NELM value is reached (which I have increased to 100).

I have a couple of technical questions:

*Does it make sense to require this precision with this functional and why/why not?
*Why is it so difficult to achieve self consistency down to a small energy tolerance?

And a more physics-related one:

*Would it make sense to run a SC PBE calculation updating the ionic positions and then run a static (NSW = 0) calculation with optB88vdW to get the correct energy? Are the fully SC optB88vdW ionic positions expected to differ substantially from the PBE ones?

Re: Convergence with the optB88vdW functional

Posted: Tue Sep 10, 2024 2:40 pm
by support_vasp

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

Best wishes,

VASP