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[fmarsusi@yahoo.com]

Dear Angelade,

 

Thank you for your response. I have run the abinit with three diferent nsyms in the input file. As you mentioned if I don't define nsym for abinit, it keeps original symmetry. If I define nsym=1, it breaks all symmetry unless identity, and the resulted geometry is very different from corresponding geometry resulted from GAUSSIAN pakage in both cases. GAUSSIAN predicts C1 final symmetric for the system ( I enter full optimization with nosymm command to GAUSSIAN).This means nsym=8. With this nsym abinit results nearly the same geometry as GAUSSIAN. This is a question for me, how abinit can underestand the final symmetry. In my case nsym=1, breaks all of 24 initial symmetry unless identity, while GAUSSIAN keeps 8 of them. So I should run one time GAUSSIAN to find final geometry, then abinit to find plane wave orbitals.

 

Best wishes,

Farah

--- On Fri, 4/24/09, Anglade Pierre-Matthieu <anglade@gmail.com> wrote:

From: Anglade Pierre-Matthieu <anglade@gmail.com>
Subject: Re: [abinit-forum] symmetry
To: forum@abinit.org
Date: Friday, April 24, 2009, 1:19 PM

Dear Farah,

I'm not quite sure to understand your question. Yet, I'll try an answer :
By default Abinit keeps the original symmetry of your system because
it exploit them to the maximum ; that is it can not find even a force
that breaks the symmetry.

If you tell abinit to use a lower level of symmetry than the actual
one, it may finds forces that break the actual symmetry. But still it
can't break the chosen level of symmetry.

In case you want a completely general relaxation you must impose "nsym
1" so that Abinit really computes forces in a general manner. In this
way you could reach any "natural" symmetry of your relaxed system by
performing a complete relaxation.

Am I answering your question?

Regards,

PMA

On Wed, Apr 22, 2009 at 9:21 AM, farah marsusi <fmarsusi@yahoo.com> wrote:
> Dear all,
>
>
>
> I know the initial symmetry of the system (Td), but do not know what is the
> final symmetry after let the system to relax by ionmov=3.  The symmetry of
> the system after relaxation is again Td, if I do not define the nsym of the
> system in the input file.
>
>
>
> I repeated the problem with the GAUSSIAN package, and did not impose to
> system to hold its symmetry during relaxation. The final symmetry of the
> system was C1.
>
>
>
> If I enter the command nsym=8 (relates to C1 symmetric) with its
> corresponding symrel in abinit input file the final geometry of abinit will
> be the same as GAUSSIAN.
>
>
>
> Is it anyway I can understand abinit to find final symmetry of the system by
> itself.
>
> Best wishes,
>
> Farah
>



--
Pierre-Matthieu Anglade