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Dear colleagues,

I tried to run NEB with VASP. I installed VTST with which I generated 8 images. So under the folder, including the first and last structures, there are 10 files (10 images). However, no matter what value I gave to the parameter IMAGES (7,8,9,10), an error message about "Error reading item IMAGES from file INCAR" will pop out. I don't know the reason. The other parameters in INCAT work fine when I didn't do a NEB calculation. I paste the INCAT file here. Does anyone knows the possible reason? Thanks! --Tina

NWRITE = 1

#Startparameter for this Run (values of parameters are equalt to default):
ISTART = 0 0=new, 1=wave, 2=same cutoff&latt (1&2 need WAVECAR file)
ICHARG = 2 0=charge from wave, 1=charge from CHGCAR, 2=atom superpos.
LWAVE=.FALSE.

Electronic Relaxation 1
ENCUT=800 planewave cutoff
NELM= 80 max number of electronic steps
EDIFF=1E-9
EDIFFG=-1E-8 force stopping-criterion for geometry steps
NELMIN=4
PREC=Normal

# Ionic Relaxation
NSW=1000 max number of geometry steps
IBRION=3 ionic relax: 0-MD 1-quasi-New 2-CG
ISIF=2 (2:force=y stress=y ions=y shape=n volume=n,
ISYM=1 1=use symmetry, 0 = no symmetry
POTIM=0.05 initial time step for geo-opt (increase for soft sys)
ICHAIN=0
LCLIMB=.True
SPRING=-5
IMAGES=10

Electronic Relaxation 2
IALGO=48 algorithm (8=CG for small, 48=RMM for big systems)
LREAL=A

LPLANE = .TRUE.
NPAR = 8
NCORE=8 up to number-of-cores-per-socket (or number-of-cores-per-node)
#NSIM = 1

I cannot reproduce this behavior with the text you pasted. Can you provide the full input files and the output as an archive, please?

Hi,

you probably missed 00 and XX as starting and endpoints, resp.

Hth,

alex

Thanks a lot for the response! Attached please found all the input data. --Tina

I believe what happened is that the file moved from a Windows system to a Unix-based one. In any case the line endings are different, which causes the INCAR reader to fail. Here are some ways you can fix this: (1) In vi you can type :set ff=unix to change all line continuations to Unix ones. (2) Add a comment at the end of every line, so that the line continuation character is not directly next to the content.

Furthermore, here are a couple of suggestions:
- VASP does not need a separate set of input files in every subdirectory anymore, so only POSCAR in every directory should be fine.
- I would recommend against putting the comments as bare text. Separate them by a comment character (# or !) instead. Otherwise these parts may be parsed.
- Please do not use both NPAR and NCORE. We recommend NCORE because it is tied to the HPC architecture.
- The number of images in the root is incorrectly set for the directory structure, it should be IMAGES = 8.

Here is a fixed INCAR file

Thanks a lot! I didn't have the error message this time!

After the calculation, I got the following results:

Forces and Energy:
0 0.000000 -554.738100 0.000000
1 0.000000 -549.615700 5.122400
2 0.000000 -553.371800 1.366300
3 0.000000 -554.809000 -0.070900
4 0.000000 -556.222100 -1.484000
5 0.000000 -557.161600 -2.423500
6 0.000000 -557.687800 -2.949700
7 0.000000 -558.035600 -3.297500
8 0.000000 -558.238700 -3.500600
9 0.000000 -558.292500 -3.554400

The forces listed here are zero. Is it normal? Or does it mean any potential issue?

Thank you for the help!
Tina

Could you provide the output of the calculation (and the input in case you changed something other than what was discussed)?

Attached are the 01 output files and the run.log file. CHG file is too large that it is not included here. The input files are the same as before with corrections. Thanks a lot!

Let me first clarify what you reported in the last post.

gu301purdue wrote: ↑Mon Jun 20, 2022 3:09 pm After the calculation, I got the following results:

Forces and Energy:
0 0.000000 -554.738100 0.000000
1 0.000000 -549.615700 5.122400
2 0.000000 -553.371800 1.366300
3 0.000000 -554.809000 -0.070900
4 0.000000 -556.222100 -1.484000
5 0.000000 -557.161600 -2.423500
6 0.000000 -557.687800 -2.949700
7 0.000000 -558.035600 -3.297500
8 0.000000 -558.238700 -3.500600
9 0.000000 -558.292500 -3.554400

The forces listed here are zero. Is it normal? Or does it mean any potential issue?

I assume the first column is the image (i.e. the directory), the second column is the energy of chain, the third column is the free energy, and the last column is the tangential force. Is this interpretation correct? If not, how did you get the data?

If the interpretation is correct, then the fact that the energy of chain (not the forces) are zero is indeed intended. In the code (chain.F) there is a comment when the nudged elastic band method is used. Only if you use positive spring constants (SPRING > 0), you expect a nonzero value there.

Thank you for the response! I don't think the last column is the force; it's the difference of the energy compared with the energy of 0 (the initial energy). You can get the value by subtracting the value with the first one.

Hi,

do I get this right: You don't know what kind of numbers you are posting here?
So I suggest you step back from all your tools and do a little more in depth analysis of your results.
If you rely on tools who are doing parts of your work, you should at least know, what's their output.

Kind regards,

alex