[Pw_forum] a possible problem in the routine add_efield.f90

[Stefano Baroni]

Dear Hanghui:

On Nov 16, 2008, at 7:27 AM, hanghui chen wrote:

> Dear PWSCF users,
>               In my previous email, I reported that if I calculated  
> a symmetric
>    system (both the material and the external sawtooth potential are
>    symmetric), I found that the forces are not symmetric. I think I  
> may find
>    the reason.
>         The total force in the presence of sawtooth potential has  
> two parts:
>    one is from the variation of Kohn-Sham functional; the other is  
> from
>    sawtooth potential which in the code is "forcefield" (see the  
> routine
>    forces.f90). The additional force is calculated by the routine
>    add_efield.f90. However in routine add_efield.f90, it only  
> calculates the
>    magnitude of the force but does not specify the direction (the  
> additional
>    force only has one direction).  Therefore all the forces in the  
> 'reversed
>    region' are not correctly calculated because the direction of  
> 'forcefield'
>    is NOT reversed as is the external electric field.

thank you very much for your thorough analysis

>         I sincerely hope that the people who wrote the routine  
> add_efield.f90
>    can reexamine the code and add the directions to the "forcefield".

I hope the same as well, however I would be even happier if you would  
volunteer to fix the code yourself and to submit the fix to the QE  
community

>         No offense intended.

of course, nobody would fel offended by your interest

cheers - SB

>
>         Thank you very much.
>    Hanghui Chen
>    Department of Physics, Yale University
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum



---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale  
de la pensée - Jean Piaget

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html






-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20081116/53e3322a/attachment.html>