It set ISIF=3 after setting IBRION=-1, I think IBRION=-1 means the ions are fixed, so what is the point to set ISIF?
How are these input files generated?
Hi @Alma. The short answer is that since NSW = 0, it does not matter than ISIF is set. VASP will not adjust the positions or cell shape/volume.
The input files are generated using Atomate, and in this particular case, it is a static calculation with INCAR settings found in pymatgen.io.vasp.sets.MPStaticSet. You can see here that the static calculation takes the prior relaxation’s INCAR settings and “updates” them, including changing NSW to 0 and IBRION to -1. It does not alter ISIF, so the ISIF value from the prior relaxation job is still present in the INCAR. Not to worry though – ISIF has no effect here.