[ase-users] NEB not exiting while maximal force is less than fmax

[Marcin Dulak]

Hi,

On 03/05/2014 11:10 PM, Boubacar Traore wrote:
>
> Dear ase users,
>
> As I'm currently working on ASE neb with siesta, I'm observing 
> something that I can't figure out.
> In my neb.py, I'm using an fmax = 0.04
> that is :
> --------------------------------
> qn = MDMin(neb, trajectory='neb.traj', logfile='neb.log')
> qn.run(fmax =0.04)
> --------------------------------
>
> When I check the evolution of the calculation using :
> ase-gui -t -g e,fmax neb.traj  > result.txt
>
> I get an fmax less than 0.04 in result.txt, which mean the calculation 
> should exit, but this is not the case.
when you use ase-gui to print fmax you get fmax for all images in 
optimizers every iteration,
note that the fmax for image[0] and image[-1] are constant (tha'ts how 
neb works).
 From ase-gui you get what's returned by "f =" in 
https://trac.fysik.dtu.dk/projects/ase/browser/trunk/ase/gui/images.py
On the other hand optimizer is clever and knows it uses neb, so it 
returns what's given by
"get_forces" in 
https://trac.fysik.dtu.dk/projects/ase/browser/trunk/ase/neb.py
Before doing any neb work please watch 
http://www.youtube.com/watch?v=wKJLRBsVt7Q
neb is not a black-box method, so don't focus too much
on getting low fmax convergence, but rather try to figure out how 
important is fmax
in your case, and how stable are the neb results.
If you find anything interesting please report to the list.

Best regards,

Marcin

>
> On the other hand, in the neb.log file, fmax is completely different 
> and give something around 0.06 and the calculation almost gets stuck 
> around this 0.06 without exiting.
>
> The total energy in both cases are the same.I checked the output file 
> of the transition point and its fmax is less than 0.04 as in 
> result.txt but the calculation is still running.
>
> I don't understand why the calculation is still on while fmax is less 
> than 0.04 in result.txt and output file (also siesta .FA file) while 
> in the neb.log file, the force is still at ~ 0.06.
>
> I see the same thing in both MDMin and FIRE optimizers!
>
> Could anyone enlighten me about this? Is there something else other 
> than fmax as an exit criteria?
>
> Best regards,
> Boubacar
>
>
> _______________________________________________
> ase-users mailing list
> ase-users at listserv.fysik.dtu.dk <mailto:ase-users at listserv.fysik.dtu.dk>
> https://listserv.fysik.dtu.dk/mailman/listinfo/ase-users
>


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.fysik.dtu.dk/pipermail/ase-users/attachments/20140306/87125aa4/attachment.html>