NEB criterion, forces

[neogien]

Hello VASP users and admin,

I did several NEB calculations and found some TSs and reaction paths I wonder however my TSs are resonable.

In my knowledge for normal geometry optimization calculations EDIFFG is the criterion. And for the NEB I should judge whether my TS is resonable with forces in the OUTCAR.
Is there any resonable guide to force values?
1eV/Ang is enough? Or should it be smaller than 0.x eV/Ang?


One more thing, sometimes my NEB jobs finish just after first ionic step even though the forces on the atoms are still high (2~3eV/Ang). I'm using IBRION=1 and default POTIM (0.5).
Do anybody can explain what the possible reason for this abnormal situation is? Shoud I change optimizer IBRION=3 with small POTIM (0.01)?

Many Thanks

HY KIM

[admin]

please note that in NEB (as in the standard implementation of VASP) the atoms only move along the hypertangents normal to the reaction path. If all relaxations were allowed, the system would relax back to the ground state. I would rather choose the change in total energies (EDIFFG>0) as convergence criterium.