My Community

hi,
I am doing some vibrational frequency calculations to check whether my optimized structure is a minimum in PES (as opposed to a transition state, etc). In the incar file I included IBRION =5, NFREE=2. Since in this method only the gamma point frequencies are calculated as stated in the manual, do I have to :
===========
(1) change my KPOINTS file to
0
Gamma
1 1 1
0. 0. 0 .
(To optimize the structure I used 4x4x1 kpts grid.)

and

(2) set NSW = 0 from NSW=200 I used to optimize the stucture.
===========

I would appreciate your reply.
Thank you.

The KPOINTS file is for "electronic" degrees of freedom, however, the "Gamma" point mentioned in VASP manual is for vibrational ones. So essentially stick with your KPOINTS file that you used in the relaxation and that should be ok.

Regarding the NSW , it depends on the version you use. So the manual says:
"Mind: In some older versions, NSW (number of ionic steps) must be set to 1 in the INCAR file, since NSW=0 resets the IBRION tag to $ -1$ regardless of the value supplied in the INCAR file. "

Thanks for replying. It was helpful.