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Hi,

I would like to run a transition state calculation by using the NEB method with vasp 5.4.4. I am totally new to this. After watching several tutorials I set up my system to run, but strangely, the energy of each images doesn't change at all. And it seems like the NEB flag wasn't executed for the calculations. Here is an example from the nebefs.pl I extracted during the run.

Image Force Stress Volume Magnet Rel Energy
0 0.00000000 0.00000000 1656.93 0.00000000 0.00000000
1 0.00000000 0.00000000 1668.46 0.00000000 0.57330000
2 0.00000000 0.00000000 1668.46 0.00000000 2.21600000
3 0.00000000 0.00000000 1668.46 0.00000000 13.51260000
4 0.00000000 0.00000000 1668.46 0.00000000 56.01490000
5 0.00000000 0.00000000 1668.46 0.00000000 14.21490000

For the individual Image, there is no energy change during the run, here is an example of one image:

1 Energy: -263.114814 Log|dE|: 2.420 SCF: 29 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 18.02m
2 Energy: -263.114835 Log|dE|: -4.690 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.30m
3 Energy: -263.114835 Log|dE|: -6.387 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.23m
4 Energy: -263.114835 Log|dE|: -7.398 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.20m
5 Energy: -263.114835 Log|dE|: -8.000 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.18m
6 Energy: -263.114835 Log|dE|: -12.000 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.18m
7 Energy: -263.114835 Log|dE|: -12.000 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.17m
8 Energy: -263.114835 Log|dE|: -12.000 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.17m
9 Energy: -263.114835 Log|dE|: -12.000 SCF: 5 Avg|F|: 0.586 Max|F|: 5.795 Vol.: 1668.5 Time: 2.17m

Here is an example of the INCAR I used:

General:
  
SYSTEM = NEB-Calc
ISYM = 0               # switch on symmetry
ISTART = 0
ICHARG = 2
#PREC = ACCURATE        # Advised to do so
ALGO = VeryFast #for checking only
PREC = normal   #for checking only
LREAL = .FALSE.
LWAVE = .FALSE.
LCHARG = .FALSE

Electronic Relaxation:

ENCUT = 360
EDIFF = 1.0E-4
NELMIN = 5

Ionic Relaxation:

EDIFFG = -0.1
NSW = 500

DOS related values:
ISMEAR = 0
SIGMA = 0.26
ISIF = 2

NEB Related:

IMAGES = 5               # Number of NEB images between the fixed endpoints
SPRING = -5.0            # The spring constant, in eV/Ang^2 between the images; negative value turns on nudging
ICHAIN = 0               # Indicates which method to run. NEB (ICHAIN=0) is the default
LCLIMB = .TRUE.          # Flag to turn on the climbing image algorithm
#LNEBCELL = .TRUE.        # Flag to turn on SS-NEB. Used with ISIF=3 and IOPT=3
                         # Must set IOPT = 3 or 7 when using LNEBCELL=.TRUE.
IOPT = 3                 # QM (Quick-Min) force based optimizers is used and good for high force far from minmum
                         # O(default vasp),1(LBFGS),2(CG),4(SD),7(FIRE)
IBRION = 3               # Disbale VASP default optimizers which are basesd on Energy
POTIM = 0                # Disbale VASP default optimizers which are basesd on Energy
MAXMOVE = 0.2           # Maximum allowed step size for translation(Default comes with IOPT=3)
TIMESTEP = 0.1           # Dynamical time step (Default comes with IOPT=3)
LSCALAPACK = .FALSE.
NPAR = 4

I have tried several different flags in the INCAR and couldn't figure out where I made the mistake. I am not sure if the VASP should be compiled with VTST code for this to work. Any suggestions where is wrong?

Thank you!
Shi

Dear shi_li,

Thank you for your question.
Indeed, you need to use VTST for the climbing image algorithm which is not supported by VASP. If you set POTIM = 0 the atoms cannot be moved and that explains why you see that the energy doesn't change.

Best wishes,
Alexey