image

[hexiujie]

I have performed a investigation of the penetration of CH4 through a monolayer using cNEB method. I choose 4 images，and the initial and final states are above and below the layer，respectively. As a result，we can see from the mep.eps that their are some energies lower than ones of initial or final states. Why？
0 0
0.05 -2.21737E-4
0.1 -7.75844E-4
0.15 -0.0015
…… ……
4.85 -0.00288
4.9 -0.00164
4.95 -0.16418E-4
5 -5.2E-4
The CONTCAR in 01,02,03,04 are positions corresponding to 1,2,3,4,5. How can I find the position corresponding to the image 4.9？I am very anxious. Any suggestions or help will be appreciated. Many thanks.

[graeme]

First, make sure that the endpoint images are fully minimized and that the NEB calculation is being done with the same settings that the endpoints were minimized. Then, if there really is a local minimum in the spline interpolation, try minimizing images 01 and/or 04. You can also use the posinterp.pl script to find an image near the interpolated minimum. For example, to get an image near 4.9, you can use 'posinterp.pl 04/CONTCAR 05/POSCAR 0.9'.

[hexiujie]

Dear graeme,
I am sure that the endpoint images are fully minimized. But there really is a local minimum in the spline interpolation. So I try minimizing images 01 and 04. Moreover I also use the posinterp.pl script to find an image near the interpolated minimum. But the CONTCAR will change a lot comparing with POSCAR,and the energies are higher than that of the endpoint images. Why？The INCAR are as follows：
PREC = Normal
ISTART = 0
ICHARG = 2
ENCUT = 400
IMAGES = 4
SPRING = -5
ICHAIN = 0
LCLIMB = T
IOPT = 2
NELM = 80
NELMIN = 2
NELMDL = -8
EDIFF = 1.E-06
#GGA = 91
#VOSKOWN = 1
LREAL = A
ALGO = Fast
EDIFFG = -0.02
NSW = 500
IBRION = 3
ISIF = 2
POTIM = 0
LPLANE = T
NPAR = 32
ISYM = 0
NSIM = 4
LWAVE = F
LCHARG = F
Is there anything wrong in INCAR？