My Community

Dear VASP community:
Short question:
I am interested if AGGAC = 0 has to be specified when BEEF-vdW is used?

More detailed explanation:

VASP-Wiki https://www.vasp.at/wiki/index.php/Nonl ... unctionals says

Note that for all vdW-DF functionals listed below except those using the rVV10 van der Waals kernel, the GGA component of the PBE correlation needs to be removed (with AGGAC=0.0)

and i always thought BEEF-vdW to be vdW-DF functional, however in list below there is no example with BEEF

ASE website https://wiki.fysik.dtu.dk/ase/ase/calculators/vasp.html specifies usage of aggac for few functionals (optb88-vdw, obptb86b-vdw, vdw-df, optpbe-vdw, vdw-df2) but beef-vdw does not contain this keyword.

Similar result is in https://github.com/jkitchin/vasp/blob/m ... sp_core.py

At the same time there are publications where people specified AGGAC in INCAR https://www.rsc.org/suppdata/c9/cp/c9cp ... 6379j1.pdf

my own tests gives confusing result: there is no AGGAC keyword in OUTCAR settings-list, also when specified. Looks like that keyword is just ignored like keyword IAMSTUPID = 1

Total energy seems to be same but i didn't made multiple tests checking everything.

Thanks a lot in advance

In short: It's not necessary to set AGGAC = 0.

Sorry for causing this confusion. This is a bit of an inaccuracy in the description on the Wiki. Basically, the BEEF functional (GGA=BF) comes with exchange and correlation combined (from the library). The tag AGGAC is ignored. There is no way to control the portion of correlation included in the functional.

This is also consistent with your tests. Does this clarify the situation for you?

Yes, thank you very much