The ABINIT Users Mailing List ( CLOSED )

[Anglade Pierre-Matthieu <anglade@gmail.com>]

Hi,

Yes in this case "chkprim 0" is the keyword to use. However you can
also "guess" the total energy of the 2x2x2 perfect supercell without a
vacancy/impurity/etc from the single cell calculation. Both ways are
correct. Yet in your case since you will perform the supercell
calculation anyway you can just forget about my comment and go ahead
with chkprim=0.

regards

PMA

PS:I'm no prof.

On Fri, Feb 27, 2009 at 9:53 AM, ren <opticalcase@gmail.com> wrote:
> Dear Prof Matthieu:
>
> Thank you for your quick reply! My apology, if I interpret correctly
> what you are saying, is that for my calculation of a 2x2x2 supercell,
> i will get the same result as a 1x1x1 unit cell except that since
> 2x2x2 supercell is much larger, the computational cost would scale to
> more than 8^3?
>
> I am making a 2x2x2 supercell as a starting point as I am considering
> vacancy in my material in the future. I read your post in the past in
> the forum, suggesting to someone that in considering a supercell (for
> a vacancy) e.g, chkprim=0 must be use? Please correct me if I am
> wrong?
>
> Regards,
> Yee Yan
>
>
>
> On Fri, Feb 27, 2009 at 1:23 AM, Anglade Pierre-Matthieu
> <anglade@gmail.com> wrote:
>> Hi,
>>
>> The transformation apparently keeps the 2x2x2 supercell.
>> In most case it is not appropriate to input chkprim =0 since you will
>> get essentially the same results has using a single cell but at
>> much more than 8 to the power three times the computational cost. Yet,
>> for a converged calculation you'll get the same properties.
>>
>> regards
>>
>> PMA
>>
>>
>> On Thu, Feb 26, 2009 at 3:48 PM, ren <opticalcase@gmail.com> wrote:
>>> Dear All,
>>>
>>> I am using Cell2Abinit.py to transform a 2x2x2 supercell of ZnO from
>>> Castep to Abinit format. I suppose that the transformation creates a
>>> primitive cell? The problem occurs when I am trying to run Abinit, the
>>> calculation halt and the log file says
>>>
>>> " According to the symmetry finder, the unit cell is
>>>   NOT primitive. The multiplicity is  8 .
>>>   The use of non-primitive unit cells is allowed
>>>   only when the input variable chkprim is 0.
>>>   Action : either change your unit cell (rprim or angdeg),
>>>   or set chkprim to 0. it says that the input structure is not a
>>> primitive cell and has a multplicity of 8."
>>>
>>> While I input chkprim = 0 and the calculation continues run may I know if
>>>
>>> 1) It is appropriate just to simply use chkprim = 0
>>>
>>> 2) Is there something i have miss out while using Cell2Abinit that the
>>> output is not a primitive cell in the end? My structure input is as
>>> below:
>>>
>>> ####################################################
>>> # Atoms Stucture created by CellToAbinit Converter !
>>> ####################################################
>>>
>>> # Definition of the unit cell
>>> #The length of the primitive vectors
>>> #                    1 Bohr=0.5291772108 Angstroms
>>> # acell 5.627901 6.498540 10.410880 Angstroms
>>> acell 10.635191 12.280461 19.673712
>>> rprim
>>>     1.000000  -0.577350  0.000000
>>>     0.000000  1.000000  0.000000
>>>     0.000000  0.000000  1.000000
>>>
>>> #Definition of the atom types
>>> #      32 kind of atoms
>>> #       ['O', 'Zn']
>>> ntypat  2
>>> znucl  8 30
>>>
>>> #Definition of tha atoms
>>> natom  32
>>> typat  1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
>>> xred
>>>    0.166667 0.333333   0.1913
>>>    0.333333 0.166667   0.4413
>>>    0.666667 0.333333   0.1913
>>>    0.833333 0.166667   0.4413
>>>    0.166667 0.833333   0.1913
>>>    0.333333 0.666667   0.4413
>>>    0.666667 0.833333   0.1913
>>>    0.833333 0.666667   0.4413
>>>    0.166667 0.333333   0.6913
>>>    0.333333 0.166667   0.9413
>>>    0.666667 0.333333   0.6913
>>>    0.833333 0.166667   0.9413
>>>    0.166667 0.833333   0.6913
>>>    0.333333 0.666667   0.9413
>>>    0.666667 0.833333   0.6913
>>>    0.833333 0.666667   0.9413
>>>    0.166667 0.333333      0.0
>>>    0.333333 0.166667     0.25
>>>    0.666667 0.333333      0.0
>>>    0.833333 0.166667     0.25
>>>    0.166667 0.833333      0.0
>>>    0.333333 0.666667     0.25
>>>    0.666667 0.833333      0.0
>>>    0.833333 0.666667     0.25
>>>    0.166667 0.333333      0.5
>>>    0.333333 0.166667     0.75
>>>    0.666667 0.333333      0.5
>>>    0.833333 0.166667     0.75
>>>    0.166667 0.833333      0.5
>>>    0.333333 0.666667     0.75
>>>    0.666667 0.833333      0.5
>>>    0.833333 0.666667     0.75
>>>
>>> ##### End of CellToAbinit Conveter ! #####
>>>
>>> The calculation runs well for a 1x1x1 and 3x3x3 cell without such
>>> these comment though.
>>>
>>> Would like to hear your advises!
>>>
>>> Regards,
>>>
>>> Yee Yan, Tay
>>>
>>> Nanyang Technological University
>>>
>>> Singapore
>>>
>>>
>>
>>
>>
>> --
>> Pierre-Matthieu Anglade
>>
>>
>
>



-- 
Pierre-Matthieu Anglade