[QE-users] Wrong number of k-points?

[Giovanni Cantele]

The symmetry k -> -k is still present even though your system has no spatial symmetry. As such the number of k-points is halved.
Giovanni

PS from a quick google search I found for example this document you might find of help
https://people.sissa.it/~degironc/FIST/Slides/8%20Symmetry.pdf

> On 31 Jan 2019, at 10:09, Laurens Siemons <laurenssiemons at hotmail.be> wrote:
> 
> Dear QE users,
> 
> I'm running a relax calculation and I encountered something that I do not understand in the output file. I used a 2 2 1 1 1 0 Monkhorst-Pack grid in my input file (which is shown below) but the output file tells me I only have 2 k-points:
> 
> 
>        116           H   tau( 116) = (   3.8845153   0.8033970  -0.3177301  )
>        117           H   tau( 117) = (   3.8658215   1.2769290  -0.3107519  )
>        118           H   tau( 118) = (   4.1682098   1.0557090  -0.6030099  )
> 
>      number of k points=     2
>                        cart. coord. in units 2pi/alat
>         k(    1) = (   0.0000000   0.0833333  -0.0984507), wk =   1.0000000
>         k(    2) = (   0.0000000   0.0833333   0.0984507), wk =   1.0000000
> 
>      Dense  grid:  5866317 G-vectors     FFT dimensions: ( 180, 160, 480)
> 
>      Smooth grid:  1484065 G-vectors     FFT dimensions: ( 108,  96, 320)
> 
> I would expect at least 4 k-point right? The system possesses no symmetry.
> 
> Thanks in advance,
> Laurens Siemons,
> PhD, University of Antwerp
> 
> &CONTROL
>   calculation = 'relax'
>   restart_mode = 'from_scratch'
>   prefix = 'a101mpa1'
>   tprnfor = .true.
>   pseudo_dir = '/data/antwerpen/204/vsc20442/pseudo/pslibrary.1.0.0/wc/PSEUDOPOTENTIALS'
>   outdir = '/scratch/antwerpen/204/vsc20442/TMP'
>   wf_collect = .true.
>   nstep = 100
> /
> &SYSTEM
>   ibrav = 0
>   A =    3.77449
>   nat = 118
>   ntyp = 5
>   ecutwfc = 60
>   ecutrho = 600
>   spline_ps = .true.
> /
> &ELECTRONS
>   electron_maxstep = 500
>   diagonalization = 'david'
>   conv_thr =  1.0d-10
>   mixing_beta = 0.70
> /
> &IONS
>   ion_dynamics = 'bfgs'
> /
> ATOMIC_SPECIES
>    O   15.99900  O.wc-n-kjpaw_psl.1.0.0.UPF
>   Ti   47.86700  Ti.wc-spn-kjpaw_psl.1.0.0.UPF
>    H   1.0079    H.wc-kjpaw_psl.1.0.0.UPF
>    C   12.0107   C.wc-n-kjpaw_psl.1.0.0.UPF
>    P   30.973761 P.wc-n-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS {crystal}
> Ti      0       0.000000        0.026316 0 0 0
> Ti      2/3     0.000000        0.026316 0 0 0
> Ti      1/3     0.000000        0.026316 0 0 0
> Ti      1/6     1/2     0.026316 0 0 0
> Ti      1/2     1/2     0.026316 0 0 0
> Ti      5/6     1/2     0.026316 0 0 0
> Ti      0       0.995856        0.266326
> Ti      1/3     0.995856        0.266326
> Ti      2/3     0.995856        0.266326
> Ti      1/6     0.495856        0.266326
> Ti      1/2     0.495856        0.266326
> Ti      5/6     0.495856        0.266326
> Ti      0       0.989202        0.145250
> Ti      1/3     0.989202        0.145250
> ...
> ...
> ...
> CELL_PARAMETERS {alat}
>   0.000000000000000   3.000000000000000   0.000000000000000
>   1.000000000000000  -0.000000000000000  -2.539341738883929
>   8.550000000000001   0.000000000000000   0.000000000000000
> K_POINTS {automatic}
> 2 2 1 1 1 0
> 
>                                                                                                                                     
> 
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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
            gcantele at gmail.com
Phone: +39 081 676910
Skype contact: giocan74
Web page: https://sites.google.com/view/giovanni-cantele

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