The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

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