[QE-users] K points in QE-6.4.1

[Pietro Delugas]

Dear Sayan

There is no problem. The code is doing what expected.  It is the input 
that is not one would expect. You have an hexagonal lattice and  you 
should specify in input  a mesh with the same number of divisions along 
the two equivalent directions.

The code checks that the set of k points you use for the BZ sum has the 
same symmetry as the lattice and adds those points which are needed 
make  the set symmetric.

It then  removes all k-points which are equivalent because of the 
crystal symmetry.  If the  crystal symmetry group is made by less 
transformations than  the lattice symmetry group then not all points 
added are removed and the number of k-points may be significantly larger 
compared with those of a mesh with  symmetric  divisions in the mesh.

regards  - Pietro

On 18/10/19 05:34, Sayan Banerjee wrote:
> Dear users,
>
> Currently I'm facing a strange number of k point generation problem in 
> QE-6.4.1. When I'm using a K-point grids of 3 x 5 x 1, it's generating 
> 34 k points whereas other combinations work fine. Please see below:
>
> K_POINTS automatic
> 5 5 1 0 0 0                                     number of k points: 13
>
>
> 4 4 1 0 0 0                                    number of k points: 10
>
>
> 3 5 1 0 0 0                                    number of k points: 34
>
> My cell parameters are-
> CELL_PARAMETERS angstrom
>         5.8236050606         0.0000000000         0.0000000000
>        -2.9118025303         5.0433899241         0.0000000000
>         0.0000000000         0.0000000000        34.8862200000
> Thanks in advance. I look forward to hearing from you.
>
> Regards,
> Sayan
> -- 
> *Sayan Banerjee*
> Graduate Student
> Department of Chemistry *|*University of Pennsylvania,
> Philadelphia, PA 19104-6323
>
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