NEB calculation error

Message

ouarda · #1 Post by **ouarda** » Thu Jun 15, 2006 7:27 am

hello all,
Itried to do neb calculation as suggested to me in the forum but Ihave got this message error :
running on 16 nodes
each image running on 2 nodes
distr: one band on 1 nodes, 2 groups
vasp.4.6.3 06Feb03 complex
01/POSCAR found : 2 types and 33 ions
LDA part: xc-table for Ceperly-Alder, standard interpolation
No initial positions read in

The POSCAR located in the 01 subdirectory is as :

fcc:
3.52
2.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 2.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 2.0000000000000000
32 1

Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 0.5000000000000000 0.0000000000000000
0.5000000000000000 0.0000000000000000 0.0000000000000000
0.2500000000000000 0.7500000000000000 0.0000000000000000
0.2500000000000000 0.2500000000000000 0.0000000000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.7500000000000000 0.2500000000000000 0.0000000000000000
0.7500000000000000 0.7500000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 0.5000000000000000
0.0000000000000000 0.5000000000000000 0.5000000000000000
0.2500000000000000 0.2500000000000000 0.5000000000000000
0.2500000000000000 0.7500000000000000 0.5000000000000000
0.5000000000000000 0.0000000000000000 0.5000000000000000
0.5000000000000000 0.5000000000000000 0.5000000000000000
0.7500000000000000 0.2500000000000000 0.5000000000000000
0.7500000000000000 0.7500000000000000 0.5000000000000000
0.2500000000000000 0.0000000000000000 0.2500000000000000
0.0000000000000000 0.2500000000000000 0.2500000000000000
0.0000000000000000 0.7500000000000000 0.2500000000000000
0.2500000000000000 0.5000000000000000 0.2500000000000000
0.5000000000000000 0.2500000000000000 0.2500000000000000
0.5000000000000000 0.7500000000000000 0.2500000000000000
0.7500000000000000 0.5000000000000000 0.2500000000000000
0.7500000000000000 0.0000000000000000 0.2500000000000000
0.2500000000000000 0.0000000000000000 0.7500000000000000
0.0000000000000000 0.2500000000000000 0.7500000000000000
0.0000000000000000 0.7500000000000000 0.7500000000000000
0.2500000000000000 0.5000000000000000 0.7500000000000000
0.5000000000000000 0.2500000000000000 0.7500000000000000
0.5000000000000000 0.7500000000000000 0.7500000000000000
0.7500000000000000 0.5000000000000000 0.7500000000000000
0.7500000000000000 0.0000000000000000 0.7500000000000000
0.2361111111111140 0.2361111111111140 0.2361111111111140

and the INCAR file is as :

ISTART = 0 ; ICHARG=2
ISMEAR = 1 ; SIGMA = 0.2
LORBIT=11
LREAL=.TRUE.
PREC = High
IALGO = 48
ENCUT = 400
ISPIN=2
SPRING=-5
IMAGES=8
IBRION=1

Can any one tell me what the problem?

Thanks for your suggestion.

konglt · #2 Post by **konglt** » Thu Jun 15, 2006 12:57 pm

Please make sure the blank line is needed. Besides, in my point of view, you should use the selective dynamics method so as to fix some atoms and allow the others to relax.

ouarda · #3 Post by **ouarda** » Thu Jun 15, 2006 1:44 pm

Thanks Konglt for response, so If I understood well, I have to add Selectives dynamics in the POSCAR file. so what atoms I must allow to relax ?
clearly, I tried to calculate the energy barier for impuritiy diffusion in 32 site supercel. In the initial state the impurtie in octaedral site (0.25, 0.25, 0.25), the final state is the First neighbour octahedral site (0.5, 0.25, 0). For this transition I created 04 intermidiates images with nebmake.pl scripts.
Now I do not know if I must fix the position impurities in all intermidiates images???

Thanks for help

konglt · #4 Post by **konglt** » Thu Jun 15, 2006 6:37 pm

First of all, ISIF = 2 should be added in your INCAR; if you are using 4 intermediate images, the tag IMAGES should be set to 4.
As to which atom should be fixed, it really depends on your systme of interest. For example, if one want to get the energy barrier of an absorbate on a surface, the bottom atoms can be fixed while the other can be set free. In your case, the atoms far away from the diffusion path can be fixed; or maybe you can set all atoms free by just adding ISIF = 2 in your INCAR, but I am not sure if this works.
Nonetheless, the diffusing atom ( the impurity atom in your case ) should never be fixed.

Hope this helps.

ouarda · #5 Post by **ouarda** » Fri Jun 16, 2006 2:05 pm

Thanks, but if I alow the impuritiy to relax it are going to return to the equilibre position (octaedral)?????

konglt · #6 Post by **konglt** » Fri Jun 16, 2006 3:37 pm

Don't worry, that is just the "nudged elastic" force's job, it will keep the diffusing atom away from the equilibrium point for the intermediate images.

ouarda · #7 Post by **ouarda** » Wed Jun 28, 2006 11:42 am

thanks for all response, but my neb calculation crash with pisitive totale energy after many days running,
I give you the INCAR and one of POSCAR's file located for example in the ../02 subderectory :
general:
SYSTEM = fcc Ni-O
ISTART = 0 ; ICHARG=2
ISMEAR = 1 ; SIGMA = 0.2
LORBIT=11
LREAL=.TRUE.
PREC = High
IALGO = 48
ENCUT = 400
spin:
ISPIN=2
SPRING=-5
IMAGES=4
IBRION=1
NSW= 5
ISIF=2

the POSCAR file :
fcc:
3.52
2.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 2.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 2.0000000000000000
32 1
Selective dynamics
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000 T T T
0.0000000000000000 0.5000000000000000 0.0000000000000000 T T T
0.5000000000000000 0.0000000000000000 0.0000000000000000 T T T
0.2500000000000000 0.7500000000000000 0.0000000000000000 T T T
0.2500000000000000 0.2500000000000000 0.0000000000000000 T T T
0.5000000000000000 0.5000000000000000 0.0000000000000000 T T T
0.7500000000000000 0.2500000000000000 0.0000000000000000 T T T
0.7500000000000000 0.7500000000000000 0.0000000000000000 T T T
0.0000000000000000 0.0000000000000000 0.5000000000000000 T T T
0.0000000000000000 0.5000000000000000 0.5000000000000000 T T T
0.2500000000000000 0.2500000000000000 0.5000000000000000 T T T
0.2500000000000000 0.7500000000000000 0.5000000000000000 T T T
0.5000000000000000 0.0000000000000000 0.5000000000000000 T T T
0.5000000000000000 0.5000000000000000 0.5000000000000000 T T T
0.7500000000000000 0.2500000000000000 0.5000000000000000 T T T
0.7500000000000000 0.7500000000000000 0.5000000000000000 T T T
0.2500000000000000 0.0000000000000000 0.2500000000000000 T T T
0.0000000000000000 0.2500000000000000 0.2500000000000000 T T T
0.0000000000000000 0.7500000000000000 0.2500000000000000 T T T
0.2500000000000000 0.5000000000000000 0.2500000000000000 T T T
0.5000000000000000 0.2500000000000000 0.2500000000000000 T T T
0.5000000000000000 0.7500000000000000 0.2500000000000000 T T T
0.7500000000000000 0.5000000000000000 0.2500000000000000 T T T
0.7500000000000000 0.0000000000000000 0.2500000000000000 T T T
0.2500000000000000 0.0000000000000000 0.7500000000000000 T T T
0.0000000000000000 0.2500000000000000 0.7500000000000000 T T T
0.0000000000000000 0.7500000000000000 0.7500000000000000 T T T
0.2500000000000000 0.5000000000000000 0.7500000000000000 T T T
0.5000000000000000 0.2500000000000000 0.7500000000000000 T T T
0.5000000000000000 0.7500000000000000 0.7500000000000000 T T T
0.7500000000000000 0.5000000000000000 0.7500000000000000 T T T
0.7500000000000000 0.0000000000000000 0.7500000000000000 T T T
0.3499999999999940 0.2500000000000000 0.1500000000000060 T T T

can tell please where is the problem
thanks for all

konglt · #8 Post by **konglt** » Wed Jun 28, 2006 12:33 pm

It is odd, but please check:
1) You intermediate images are linear interpolation of the initial and final state;
2) The sequence of POTCAR is correct.
...

ouarda · #9 Post by **ouarda** » Wed Jun 28, 2006 1:23 pm

1) for the interpolation, I used the nebmake.pl script dowonloaded at http://theory.cm.utexas.edu/vtsttools/scripts/
2)the sequence of potcar is correct

konglt · #10 Post by **konglt** » Wed Jun 28, 2006 5:52 pm

Besides, your initial state and final state should be relaxed before running the neb. Please relax your configuration first and then try again.