VASP Forum

I am trying to calculate VASP intensities with Raman Python script by Fornari https://github.com/raman-sc/VASP
Calculation fails - I am contacting Fornari about it. but one error comes from VASP and I do not understand why. Fatal error! IBRION=0, but no entry for POTIM on file INCAR. MUST be specified!!

I just want to run some single point calculation - I suppose. I do not quite understand this error, can somebody please advise? Perhaps that will help Python Raman intensity calculation to proceed

running on 256 total cores
distrk: each k-point on 256 cores, 1 groups
distr: one band on 8 cores, 32 groups
using from now: INCAR
vasp.5.4.4.18Apr17-6-g9f103f2a35 (build Jun 14 2024 12:30:39) gamma-only
POSCAR found type information on POSCAR Si O H W
POSCAR found : 4 types and 253 ions
Fatal error! IBRION=0, but no entry for POTIM on file INCAR. MUST be specified!!
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Hello!

It seems to me that the INCAR file has some tags set which cause VASP to perform an unintended MD simulation. My guess is that setting NSW in your INCAR file

...
NSW       =   1500
...

triggers IBRION to change from -1 (no ionic update) to 0 (MD simulation). For MD simulations a time step has to be set by the user via the POTIM tag. Because it was not found in your INCAR VASP is complaining and exiting.

You could try to remove the NSW line in your INCAR and run the script again! Although I have never used the script it seems to me that for some steps you need to explicitly set IBRION = 5,6,7 or 8, please consult the documentation of the script for the details.

All the best,
Andreas Singraber

thank you for your help