[Pw_forum] What to do when NEB calculation is difficult to converge?
Xunlei Ding
ding at sissa.it
Sun Aug 27 09:51:36 CEST 2006
I forgot to give the errors for the last iteration.
image energy (eV) error (eV/A) frozen
1 -37090.9593488 0.017636 T
2 -37090.9338352 0.063849 F
3 -37090.8813092 0.184154 F
4 -37090.8113275 0.294601 F
5 -37090.6869583 0.182737 F
6 -37090.8612055 0.071489 F
7 -37091.1264731 0.013874 T
Yours,
Ding
Xunlei Ding wrote:
> Dear all,
> I am now doing a neb calculation on a surface adsorption system with
> pwscf3.0
> The default values are used in the calculation as below:
> calculation = neb
> restart_mode = restart
> opt_scheme = quick-min
> num_of_images = 7
> nstep = 500
> first_last_opt = F
> coarse-grained phase-space = F
> use_freezing = F
> ds = 1.0000 a.u.
> CI_scheme = highest-TS
> k_max = 0.6169 a.u.
> k_min = 0.6169 a.u.
> path_thr = 0.1000 eV / A
> initial path length = 12.2601 bohr
> initial inter-image distance = 2.0434 bohr
>
> It has more than 400 iterations and has not converged. Should I change
> some settings, such as ds, or k_max and k_min?
> Below are the activation energies for the last few iterations, and
> they are not monotone decreasing but oscillating.
> Would anybody give me some suggestions?
>
> activation energy (->) = 0.273443 eV
> activation energy (->) = 0.273431 eV
> activation energy (->) = 0.273719 eV
> activation energy (->) = 0.273765 eV
> activation energy (->) = 0.273207 eV
> activation energy (->) = 0.273148 eV
> activation energy (->) = 0.273311 eV
> activation energy (->) = 0.273501 eV
> activation energy (->) = 0.272957 eV
> activation energy (->) = 0.272818 eV
> activation energy (->) = 0.272865 eV
> activation energy (->) = 0.273155 eV
> activation energy (->) = 0.272750 eV
> activation energy (->) = 0.272463 eV
> activation energy (->) = 0.272443 eV
> activation energy (->) = 0.272777 eV
> activation energy (->) = 0.272574 eV
> activation energy (->) = 0.272118 eV
> activation energy (->) = 0.272080 eV
> activation energy (->) = 0.272367 eV
> activation energy (->) = 0.273228 eV
> activation energy (->) = 0.272663 eV
> activation energy (->) = 0.272621 eV
> activation energy (->) = 0.272935 eV
> activation energy (->) = 0.273033 eV
> activation energy (->) = 0.272427 eV
> activation energy (->) = 0.272386 eV
> activation energy (->) = 0.272558 eV
> activation energy (->) = 0.272823 eV
> activation energy (->) = 0.272391 eV
>
> Yours,
> Ding
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