The ABINIT Users Mailing List ( CLOSED )

[matthieu verstraete <Matthieu.Verstraete@ulg.ac.be>]

Hello Martin,

1) you are using symmorphi 0. This means all symops with a translation
will be neglected, and the atoms may relax wrt them. At the end,
feeding the coordinates back into abinit, it will see the change in
spgroup. I suspect this is the main difference between the two
tetragonal groups.

2) You are fixing the number of kpoints by hand. This is a bit
strange, and risky, as you may be breaking symmetry in the k-grid if
you do not get things right. It's safer to give ngkpt or kptrlatt,
plus the shifts, and let abinit figure out nkpt. I realize this is a
bit more of a pain as you have to add istwfk nkpt*1 - on most
platforms you can write "istwfk *1" and it will fill the needed number
of values with 1.

Ciao

Matthieu

2010/2/2 Martin Häufel <martin.haeufel@googlemail.com>:
> Dear Xavier, dear ABINIT users,
>
> please see attached file (input file). The symmetry group of the output
> crystal structure is:
>  space group P-4 m 2 (#115); Bravais tP (primitive tetrag.)
>
> While tetragonal zirconia has space group P4_2/n m c (#137), which was used
> as starting point for the whole optimization.
>
> Best regards,
>
> Martin Haeufel
> TU Munich, WSI (T33)
> www.wsi.tum.de
>
>
> On 02.02.2010 17:46, Xavier Gonze wrote:
>>
>> On 02 Feb 2010, at 16:43, Martin Haeufel wrote:
>>>
>>> @Xavier, all ABINIT users: Question
>>>
>>> There's another thing I would like to point out:
>>>
>>> If you start with optcell 0 and then continue with optcell 2, you might
>>> end up with a different crystal symmetry.
>>
>> In principle, no ...
>>
>>>
>>> Why is that? Well, in step 1 the structure symmetry might change,
>>> because it corresponds to energetically more favourable ionic positions.
>>
>> In principle no : the symmetries are used to symmetrize the atomic
>> positions.
>>
>>> But in step 2 the symmetry is fixed to the input symmetry, which is now
>>> the output of step 1!
>>>
>>> Is that correct?
>>
>> If you have observed such a behavior, please could you post your input
>> files,
>> so that they can be examined ?
>>
>> Best regards,
>> X.
>>
>>
>
>



--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Prof. Matthieu Verstraete

Universite de Liège
Institut de Physique, Bat. B5, 3/7
Allée du 6 aout, 17
B- 4000 Sart Tilman, Liège
Belgium

Associate member European Theoretical Spectroscopy Facility (ETSF
http://www.etsf.eu)

Phone : +32 4 366 90 17
Fax   : +32 4 366 36 29

Mail : matthieu.verstraete@ulg.ac.be
         matthieu.jean.verstraete@gmail.com



-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Prof. Matthieu Verstraete

Universite de Liège
Institut de Physique, Bat. B5, 3/7
Allée du 6 aout, 17
B- 4000 Sart Tilman, Liège
Belgium

Associate member European Theoretical Spectroscopy Facility (ETSF
http://www.etsf.eu)

Phone : +32 4 366 90 17
Fax   : +32 4 366 36 29

Mail : matthieu.verstraete@ulg.ac.be
          matthieu.jean.verstraete@gmail.com