[Wien] precision problem

[Torsten Andersen]

Hi Kevin,

you are of course right, it is not really an error.

Best regards,
Torsten.

Jorissen Kevin wrote:
> Hi Torsten,
> what you say is correct, only I would not call it an error.
> Equivalency is determined by two things :
> * equivalent atoms must have identical chemical environment
> * there must be a symmetry operation of the lattice connecting equivalent atoms.
>  
> Nn checks the first condition, and sgroup takes care of the second one.  Obviously the second condition will sometimes reduce the equivalency obtained by the first condition only.
> So after running nn, one must always run sgroup also.  Even if one chooses to ignore the lattice changes proposed by sgroup (CXZ!), one *must* check that the equivalency is not changed by symmetry.
>  
> Kevin.
>  
> 
> 	-----Oorspronkelijk bericht----- 
> 	Van: Torsten Andersen [mailto:thor at physik.uni-kl.de] 
> 	Verzonden: wo 11/5/2003 10:02 
> 	Aan: wien at zeus.theochem.tuwien.ac.at 
> 	CC: 
> 	Onderwerp: Re: [Wien] precision problem
> 	
> 	
> 
> 	Dear stargmoon,
> 	
> 	I am not sure what your problem is, but I would say that if symmetry and
> 	  sgroup does not complain and sgroup does not reduce the unit cell, it
> 	is safe to ignore this error. I have sometimes gotten it when I
> 	calculate thin films, and nn wants two atoms to be equal although they
> 	by symmetry are not.
> 	
> 	Best regards,
> 	Torsten Andersen.
> 	
> 	stargmoon wrote:
> 	> Dear wien2k user,
> 	> 
> 	> I met a problem in doing 'x nn'. My input structure is the structure
> 	> with space group P-3m1, and one type of atoms occupy the "6i"
> 	> positions.I think I can be sure that my input structure is correct,
> 	> because the space group analysis with wien2k and other software all
> 	> indicate the right space group. However, after the 'x nn' finished, I
> 	> always got the error information, that is, the Mult not equal and ityp
> 	> not equal. I checked the number and the distance of the nearest
> 	> neighbors printed out in the file case.outputnn, but I can't find out
> 	> any difference between those atoms which was declared to be not equal by
> 	> 'x nn'. Have you ever met the same problem, and can I ignore those error
> 	> (because the space group is the same as expected)?
> 	> 
> 	> Thanks for your reply!
> 	> 
> 	> Best,
> 	> 
> 	> stargmoon
> 	>
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> 	
> 	--
> 	Dr. Torsten Andersen                     TA-web: http://deep.at/myspace/
> 	AG Hübner, Department of Physics, Kaiserslautern University, and
> 	Condensed Matter Theory Group, Department of Physics, Uppsala University
> 	Web: http://www.fysik4.fysik.uu.se/         http://www.physik.uni-kl.de/
> 	
> 	
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-- 
Dr. Torsten Andersen                     TA-web: http://deep.at/myspace/
AG Hübner, Department of Physics, Kaiserslautern University, and
Condensed Matter Theory Group, Department of Physics, Uppsala University
Web: http://www.fysik4.fysik.uu.se/         http://www.physik.uni-kl.de/