[Wien] In the calculation of elastic properties why ​​​​​rhombohedral lattice parameter needs same k-mesh as used in pristine case

[Dr. K. C. Bhamu]

Dear Luis,
init_lpaw did not rotate the cell.

Anyway, I could break the loop and it took the uniform mesh that I used in
the pristine case.
But I still want to know the reason.


regards
Bhamu


On Fri, May 17, 2019 at 5:17 PM Luis Ogando <lcodacal at gmail.com> wrote:

> Dear Bhamu,
>
>     Please, check if init_lpaw did not rotate your cell. Perhapes
> 18.184512 is now at y axis, b parameter.
>    All the best,
>              Luis
>
> Em sex, 17 de mai de 2019 às 07:49, Dr. K. C. Bhamu <kcbhamu85 at gmail.com>
> escreveu:
>
>> Dear Wien2k users,
>>
>> I am running a cubic (F) system having a=b=c=10.446600Bohr. The default
>> k-mesh size is 14 14 14 (3000kpt in FBZ).
>> I applied tetragonal and rhombohedral strain on optimized lattice
>> parameters (on above a,b,c) and the resultant strained a/b/c are
>> 10.429247/10.429247/10.481393 Bohr for tetragonal strain and 7.386862/
>> 7.386862/18.184512 Bohr for rhombohedral strain.
>>
>> My script advise me to use 20 20 8 kmesh size for the rhombohedral case
>> and "14 14 14" (as there is only slight change in a/b/c) for tetragonal
>> case.
>>
>> But for the rhombohedral case I am not able to use 20 20 8 mesh size and
>> the kgen program suggest me to use equal mesh in x and z direction (see
>> below in blue).
>>
>> Could you someone please advice me why I can not use the mesh size  20 20
>> 8 for the rhombohedral case?
>>
>> I may be convinced about my doubt because I am having  equal "length of
>> reciprocal lattice vectors:   1.041   1.041   1.041".  Am I right? If
>> so, then also I need to know why a lattice parameter which is almost double
>> in one direct wrt original cubic latice need the same k-points as used in
>> case of cubic case. The answer may be somewhere in symmetry operations but
>> I could not completely understand it.
>>
>>
>>
>>            6  symmetry operations without inversion
>>  inversion added (non-spinpolarized non-so calculation)
>>   NUMBER OF K-POINTS IN WHOLE CELL: (0 allows to specify 3 divisions of G)
>> 0
>>  length of reciprocal lattice vectors:   1.041   1.041   1.041   0.000
>> 0.000   0.000
>>   Specify 3 mesh-divisions (n1,n2,n3):
>> 20 20 8
>>  Lattice symmetry requires equal mesh in x and z direction
>>   Specify 3 mesh-divisions (n1,n2,n3):
>>
>>
>> regards
>> Bhamu
>>
>>
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