Convergence problem in NEB calculation

Message

chengz · #1 Post by **chengz** » Wed Apr 13, 2011 7:21 pm

I've been trying to perform VASP calculations for my system, especially organic molecules reaction on metal oxide surface (WO3).
The calculations are OK in case of geometry optimization.

However, I can not find transition state with NEB method. Each of the images do not converge even after 200 runs.
I'm afraid I have used inapproprate variables in INCAR options

My INCAR settings for NEB calculations are

SYSTEM = NEB
SPRING = -5
IMAGES = 4
PREC = High
ENCUT = 400.000
IBRION = 2
NSW = 200
ISIF = 2
ALGO = Normal (blocked Davidson)
NELM = 60
NELMIN = 2
EDIFF = 1.0e-05
EDIFFG = -0.02
VOSKOWN = 1
NBLOCK = 1
ISPIN = 1
INIWAV = 1
ISTART = 0
ICHARG = 2
LWAVE = .TRUE.
LCHARG = .TRUE.
ADDGRID = .FALSE.
ISMEAR = 1 ! methfessel-paxton
SIGMA = 0.1 !
LREAL = .FALSE.
RWIGS = 1.30 0.73 0.77 0.32

Look forward to your help. Thank you very much! &| &| &|

boris · #2 Post by **boris** » Wed Apr 13, 2011 7:37 pm

Hi

IBRION= 2 fails in the case of NEB calculations. Try with IBRION= 1 instead.

B.

kambiz · #3 Post by **kambiz** » Thu Apr 14, 2011 5:04 am

Hi,

or you can try damped MD (IBRION = 3) with a proper time step.

Cheers

chengz · #4 Post by **chengz** » Thu Apr 14, 2011 6:37 am

Thank you so much, I will try IBRION=1 and 3, respectively.

If IBRION=3, POTIM=0,
IOPT should be 0 or 1 ?

kambiz · #5 Post by **kambiz** » Fri Apr 15, 2011 1:25 am

I usually set it between 0.1 to 0.2, with IBRION = 3.

I think that POTIM = 0 means that ions should not be moved. yes???

Cheers