[Pw_forum] cannot bracket Ef

[Eyvaz Isaev]

Dear Marcelo,

Inspecting of your files have shown that, 

1. You used too low cutoff energy for norm-conserving pseudos. 15Ry is really very small, you should use around 60Ry for  these pseudos, but you can check, if you like (via total energy, of course)
2. As you have a rather large system  use only G-point (K_POINTS  gamma) technique.
3. I would prefer mixing_mode='local-TF'
4. Use smaller mixing coefficient, say, 0.1.
5. Try without MIXING_NDIM (i.e. by default)
6. Try smaller upscale parameter (say, 20)
 
It seems there is a nasty with your structure at the last iteration. The error might be due to one of that  above mentioned.  But it might be a structure change that  requires  more bands you expect. Using smearing only and nband by default sometime fails.   
 Usually not converged structure during 100-200 iteration is a sign that something is wrong with your structure setup (suggesting that others are OK). 

Bests,
Eyvaz.
-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Mon, 8/9/10, Marcello Rosini <marcello.rosini at unimore.it> wrote:

> From: Marcello Rosini <marcello.rosini at unimore.it>
> Subject: [Pw_forum] cannot bracket Ef
> To: pw_forum at pwscf.org
> Date: Monday, August 9, 2010, 11:24 AM
> Dear all
> I got this error from a relax calculation
> 
>   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>       from efermig : error #   
>      1
>       internal error, cannot braket Ef
>   %%%%%%%%%%%%%%%%%%%%%%%%%%%
> 
> I am using a smearing, thus I do not have the problem of
> unsufficient 
> number of bands.
> The program makes a number of relaxations cycles and then
> stops.
> I did not find anything useful from the older post in the
> forum.
> 
> Here find the input and the output
> http://cdm.unimo.it/home/fisica/rosini.marcello/pwerror.tgz
> 
> Any suggestion?
> thanks
> Marcello
> 
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