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Hi,

I'd like to use the FERWE and FERDO tag in the INCAR file to calculate the energy of singlet and triplet excitonic polarons.

for a system containing 640 electrons, the following works for a single k-point calculation:

(singlet)
NBANDS = 640
FERWE = 319*1 0 1 319*1
FERDO = 319*1 1 0 319*1

(triplet)
NBANDS = 640
FERWE = 319*1 1 1 319*1
FERDO = 319*1 0 0 319*1

However, for 4x4x4 k-points, 30 k-points in the IBZ according to the outcar, I receive the error message "Error reading item 'FERWE' from file INCAR."

For this I have repeated for example the string " 319*1 0 1 319*1" 30 times, so:

FERWE = 319*1 0 1 319*1 319*1 0 1 319*1 319*1 0 1 319*1 319*1 0 1 319*1 319*1 0 1 319*1 etc. (30 times total)

The number of bands and the number of kpoints should thereby match with the occupation set by FERWE/FERDO.

What could be the origin of this problem?
I've provided an example of the input files that generates this error in the attachment.

Kind regards,

Jeffrey

Dear Jeffrey,

Could you check in your OUTCAR file if the number of bands that VASP is going to use is indeed 640? Keep in mind that this number can change depending on how you set up your job parallelisation. See here wiki/index.php/FERWE.

Kind regards,
Pedro