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["Josef W. Zwanziger" <jzwanzig@dal.ca>]

Will do! Thanks!!!

BTW, is 5.4.3 using bzr or baz?

Josef W. Zwanziger                                 
Prof. of Chemistry
Canada Research Chair in NMR Studies of Materials
Director, Atlantic Region Magnetic Resonance Centre
Dalhousie University
Halifax, NS B3H 4J3 
Canada

tel: 902.494.1960     net: jzwanzig@dal.ca
fax: 902.494.1867     web: http://jwz.chem.dal.ca


-----Original Message-----
From: Xavier Gonze [mailto:gonze@pcpm.ucl.ac.be] 
Sent: August 28, 2007 2:05 PM
To: forum@abinit.org
Subject: Re: [abinit-forum] Cell optimization and symmetry breaking


Dear Joe,

I have added a subroutine strainsym.F90 in ABINITv5.4.3 , that should
enforce the symmetry on the unit cell. None of the automatic tests were
affected by this modification (this is not a surprise), so that I lack a
test to see whether this modification does the work or not. I would be very
glad if you could test it, either from the official  
v5.4.3 in a few days ,
or earlier, by downloading the nearly final v5.4.3 from the repository
(abinit-release--merge-private--5.4.3--patch-35)

Best regards,
Xavier


On 27 Aug 2007, at 14:24, jzwanzig@dal.ca wrote:

> Dear colleagues,
>
> I find that when minimizing the forces in a crystal structure, say
> by doing a run with "ionmov 2" and "optcell 2" the resulting output  
> structure (acell, rprim, xred) together breaks the original input  
> symmetry. Never by much, but certain symmetry operations will have  
> residuals of around 1E-7, which is worse than the built-in 1E-8  
> threshold. So the symmetry of the "optimized" structure is lower  
> than the original input. Sometimes this is easy to detect, for  
> example when all the atoms are on high symmetry positions and the  
> acell variable is "optimized" to (for example) "1.11111111  
> 1.11111111 1.11111112". However, some unit cells I work with have  
> complicated shapes but still some symmetry. Why does the  
> optimization run break symmetry in this way? Is there a setting I  
> should be using that I don't know about?
>
> Thanks,
>
> Joe Zwanziger
>