UT theoretical chemistry code forum

Dear professor:
I got the problem while using NEB calculation to find the energy barrier. My energy curve produces well at first. After seven ionic steps my eighth image energy rises highly. I observe my eighth image by VMD and find the dissociating N2 vibrates on the surface. Finally the N2 dissociated to N atom and crash the surface to produce system exploding. There is the content of my INCAR:

System = NEB
ISMEAR = -1
SIGMA = 0.1
EDIFF = 1E-4
EDIFFG = -0.2
NSW = 1000
ENCUT = 600
ALGO = Fast
ISIF = 2
GGA = 91
IBRION = 3
POTIM = 0.05
LREAL = A
NPAR = 8
NELM = 100
LWAVE = F
LCHARG = F
IMAGES = 8
SPRING = -5.0
What's wrong with my system? Thanks for your help!

This is a bit hard to debug without looking at the run, but here are a few things to try:

Check the initial band, for example as a movie with VMD, and make sure there is no discontinuity at the last image.

More likely, there are high forces due to the N2 bond breaking. Try being even more conservative with POTIM, for example, setting it to 0.01 until the forces drop below 0.5 eV/Ang.

If this doesn't solve the problem, send the files if you want us to take a look at it.