[Pw_forum] BUG in NEB calculations with tefield=true

[Lorenzo Paulatto]

do you have an example input that fails and can be run in a reasonable time?

On 06/11/17 15:55, Maxim Skripnik wrote:
> Dear developers,
> 
> I'd like to report a strange behavior of neb.x when one sets
> tefield=true and dipfield=true. The error of the first image becomes
> very large even though the xyz coordinates in FIRST_IMAGE are properly
> relaxed. This seems to be not an issue for the actual neb calculation
> since neb.p finds the energy barrier anyway. Nevertheless, it leads to a
> corrupt .path file, which contains either ********** or/and NaN. When
> one wants to restart the neb calculation (e.g. when going from
> CI_scheme='no-CI' to 'auto'), is crashes since neb.x reads the corrupted
> .path file which contains ******* and NaN.
> I took a look at the pw.x calculation of the first image, which is done
> only once at the beginning of a neb calculation (stored in
> prefix/neb_1/PW.out). And already there one can see the problem:
> 
> end of prefix/neb_1/PW.out:
> 
> ...
> ...
> ...
> 
>        convergence has been achieved in  26 iterations
> 
>        Writing output data file neb.save
> 
> Forces acting on atoms (Ry/au):
> 
>        atom    1 type  2   force = ************** NaN**************
>        atom    2 type  2   force = ************** NaN**************
>        atom    3 type  2   force = ************** NaN**************
>        atom    4 type  2   force = ************** NaN**************
> ...
> ...
> ...
> 
>        Total force =          NaN     Total SCF correction = 0.000109
> 
> Interestingly, this doesn't happen with the last image, which was
> relaxed with exactly the same pw.x settings. This happens even with
> eamp=0, as long as tefield=true and dipfield=true. I was able to
> reproduce the behavior with QE 6.0 and 6.1 on two totally different
> computer clusters. Any idea why this happens?
> 
> Best regards
> Maxim Skripnik
> University of Konstanz
> 
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-- 
Lorenzo Paulatto - Paris