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Transition State Search through CI-NEB

PostPosted: Tue Oct 24, 2017 10:26 am
by seemagautam
Hello Everyone,

I am interested in locating the transition state (TS) either through CI-NEB or Dimer method. However, I am facing difficulty in finding TS or minimum energy path (MEP) through CI-NEB. Main problem is energy convergence. I am studying CO2 activation over the transition carbide system. Problem is NEB calculations are not converging. If converges then energy of TS is lower than the the initial and final state. One more thing I want to ask the importance of MAGMOM tag for the TS search. I have also tried Dimer Method also. but I think that is the refinement of CI-NEB. Please help me in locating transition state. And as slab calculations are computationally expensive, then how can we make the NEB calculations fast in VASP.

INCAR, I am using is :
SYSTEM= transition state
PREC=Med
EDIFF=1e-04
EDIFFG=-0.01

ISMEAR=1
SIGMA=0.1
VOSKOWN=1
IBRION=3

#IBRION=1
LCLIMB=.TRUE
ICHAIN=0
SPRING=-5
LREAL=Auto

IMAGES=4
ISIF=2
POTIM=0.01
#POTIM=0.3

NSW=1000
ISPIN=2
MAGMOM= 33*2 2*1 32*4 1*2
ENCUT= 450

My Best Regards,
Seema Gautam

Re: Transition State Search through CI-NEB

PostPosted: Wed Oct 25, 2017 12:48 pm
by alex
Hi Seema,

check your sentence: 'If converges then energy of TS is lower than the the initial and final state'.
This is probably the major source of your difficulty. They need to be lower than the TS you are searching.

Cheers,

alex

Re: Transition State Search through CI-NEB

PostPosted: Tue Oct 31, 2017 5:25 am
by seemagautam
Dear Alex,

Thanks a lot for reply,

By this sentence 'If converges then energy of TS is lower than the the initial and final state' ", I mean that when my NEB job completes, then I am getting TS of lower energy than IS and FS. However, To get activation energy or Barrier height, energy of TS should be higher than that of IS and FS. Please help me in solving this issue. Also please give some suggestions about dimer method.

Once again thanks a lot.
Waiting for your reply,

Best Regards,
Seema Gautam