For studying a bulk supercell, after creating some vacuum in it, I'm confused about how to relax it.
With VASP, I can do relaxation using
NSW = 0 and
ISIF tag 2 or 3.
Alternatively, I could set
NSW=100 and with some value for
ISIF (not sure what would be best).
A third option is to first relax the supercell, then after creating a vacuum, it is should be fine to select
ISIF=0 for relaxation.
I am not sure which one of these is the best option or whether there is a better alternative.