# [Pw_forum] problem with K_POINTS introduced by hand (input and output files enclosed)

Giovanni Cantele giovanni.cantele at spin.cnr.it
Thu May 7 11:09:23 CEST 2015

```I tried to run your input with both the k-point grid you provided and with
K_POINTS (automatic)
4  4  4    1  1  1

but no symmetry and 32 k-points are found in both cases. The reason why pw.x does not uses only the then k-points you provide is that it understands that you provide a k-point grid that is compatible with some symmetry but that symmetry is not found. So, if two k-points, let’s say k1 and k2, are equivalent by symmetry, the run should use only k1 with weight 2 , but if symmetry is not found the grid you provide is “completed” so as to span the full Brillouin zone.

So the problem is reverted to why symmetry is not found. The reason is that (I guess) you specify atomic coordinates in flat coordinates, whereas they are likely to be expressed in crystal coordinates.

If you try to replace
ATOMIC_POSITIONS (alat)
with
ATOMIC_POSITIONS (crystal)

with
K_POINTS (automatic)
4  4  4    1  1  1
then pw.x correctly (unless other possible errors in the input file!) gives you 12 Sym.Ops. (with inversion) and
number of k points=   10  gaussian broad. (Ry)=  0.0050     ngauss =  -1
cart. coord. in units 2pi/a_0
k(    1) = (   0.0000000   0.0000000   0.1304249), wk =   0.0625000
k(    2) = (  -0.5057234  -0.2919796   0.2173748), wk =   0.1875000
k(    3) = (   1.0114469   0.5839591  -0.0434750), wk =   0.1875000
k(    4) = (   0.5057234   0.2919796   0.0434750), wk =   0.1875000
k(    5) = (  -0.5057234   0.2919796   0.3043247), wk =   0.1875000
k(    6) = (   1.0114469   1.1679182   0.0434750), wk =   0.3750000
k(    7) = (   0.5057234   0.8759387   0.1304249), wk =   0.3750000
k(    8) = (   1.0114469  -0.5839591  -0.2173748), wk =   0.1875000
k(    9) = (   0.0000000   0.0000000   0.3912746), wk =   0.0625000
k(   10) = (   1.5171703   0.8759387   0.1304249), wk =   0.1875000

Visualizing the structure with xcrysden would have been helpful to understand that the input structure you provided were not what you want to provide!!

Also, if you want to use k-points provided by another code, be sure that the reciprocal (or direct) vector defining the unit cell are the same in both codes, because
there can be more than one choice on the unit cell vectors.

Giovanni

> On 07 May 2015, at 10:44, Manuel Pérez Jigato <manuel.perez at list.lu> wrote:
>
> hi again
>
> just in case this information could be helpful, let me add to my former message that the original k-point set generated with abinit and introduced by hand
> in order to run pwscf, are based on a monkhorst-pack grid  4x4x4, which is shifted by 1/2 1/2 1/2. On the other hand, the correct space group is ITA number 166
> (R-3m:R), ie the primitive cell with 4 atoms
>
> thanks a lot
>
> Manuel
>
> Dr Manuel Pérez Jigato, Chargé de Recherche
> Luxembourg Institute of Science and Technology (LIST)
> Materials Research and Technology (MRT)
> 41 rue du Brill
> L-4422 BELVAUX
> Grand-Duché de Luxembourg
> Tel (+352) 47 02 61 - 584
> Fax (+352) 47 02 64
> e-mail  manuel.perez at list.lu <mailto:manuel.perez at list.lu>
>
>
> <graycol.gif>Manuel Pérez Jigato ---07/05/2015 10:33:09---hello I am a newcomer to pwscf, and I would like to report a problem with the
>
> From:	Manuel Pérez Jigato <manuel.perez at list.lu <mailto:manuel.perez at list.lu>>
> To:	"PWSCF Forum" <pw_forum at pwscf.org <mailto:pw_forum at pwscf.org>>,
> Date:	07/05/2015 10:33
> Subject:	[Pw_forum] problem with K_POINTS introduced by hand (input and	output files enclosed)
> Sent by:	pw_forum-bounces at pwscf.org <mailto:pw_forum-bounces at pwscf.org>
>
>
>
> hello
>
> I am a newcomer to pwscf, and I would like to report a problem with the K_POINTS option of the input file. When I try to input the k-points by hand,
> the program pwscf runs fine, but, only after generating a completely different set of k-points, ie, ignoring my input K-POINT data.(See attached file: dela.out)
> For a rhombohedral cell (ibrav 5), I have introduced in the input 10 kpoints, which originally where generated as the probably most economic set
> (pwscf generates 32 points, but it is unclear to me whether they correspond to the full-zone or else, to the IBZ). I have generated the 10 k-points
> from abinit, and they are expressed in "reduced/fractional-coordinates", which I seem to match to the option "crystal" in K_POINTS entry of pwscf
> (for me it is important to have exactly the same k-points in both programs).  If you look inside the output file file.out from the pwscf run, the first strange
> thing that turns up is  "No symmetry found", and the second thing is the 32 k-points, which, furthermore, all have the same weight, consistently with
> the full zone
>
> will you please clarify this further? in case this is a symmetry problem, will you please let me know where in the input file I have made a mistake?
>
> thanks a lot
>
> Manuel
>
> PS the input file is
>
> &control
> calculation='scf'
> prefix='delacubo2'
> restart_mode='from_scratch'
> pseudo_dir='./'
> outdir='./'
> tstress=.true.
> tprnfor=.true.
> /
> &system
> ibrav=5
> celldm(1)=10.85761474894d0
> celldm(4)=0.87781332d0
> nat=4
> ntyp=3
> ecutwfc=30.0D0
> occupations='smearing'
> smearing='marzari-vanderbilt'
> degauss=0.005D0
> nbnd=24
> /
> &electrons
> mixing_mode='plain'
> mixing_beta=0.7D0
> startingwfc ='atomic'
> conv_thr=1.D-08
> diagonalization='david'
> /
> ATOMIC_SPECIES
> Cu 63.546 cu.upf
> B  10.811  b.upf
> O  15.999  o.upf
> ATOMIC_POSITIONS (alat)
> Cu 0.00000 0.00000 0.00000    0  0  0
> B  0.50000 0.50000 0.50000    0  0  0
> O  0.11111 0.11111 0.11111    0  0  0
> O  0.88889 0.88889 0.88889    0  0  0
> K_POINTS (crystal)
> 10
>                     1.25000000E-01  1.25000000E-01  1.25000000E-01  1
>                     3.75000000E-01  1.25000000E-01  1.25000000E-01  3
>                    -3.75000000E-01  1.25000000E-01  1.25000000E-01  3
>                    -1.25000000E-01  1.25000000E-01  1.25000000E-01  3
>                     3.75000000E-01  3.75000000E-01  1.25000000E-01  3
>                    -3.75000000E-01  3.75000000E-01  1.25000000E-01  6
>                    -1.25000000E-01  3.75000000E-01  1.25000000E-01  6
>                    -3.75000000E-01 -3.75000000E-01  1.25000000E-01  3
>                     3.75000000E-01  3.75000000E-01  3.75000000E-01  1
>                    -3.75000000E-01  3.75000000E-01  3.75000000E-01  3
>
> -----------------------------------------------------------------------------------------------------
>
> Dr Manuel Pérez Jigato, Chargé de Recherche
> Luxembourg Institute of Science and Technology (LIST)
> Materials Research and Technology (MRT)
> 41 rue du Brill
> L-4422 BELVAUX
> Grand-Duché de Luxembourg
> Tel (+352) 47 02 61 - 584
> Fax (+352) 47 02 64
> e-mail  manuel.perez at list.lu <mailto:manuel.perez at list.lu>[attachment "dela.out" deleted by Manuel Pérez Jigato/LIST] _______________________________________________
> Pw_forum mailing list
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--

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele

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