[Pw_forum] high symmetry point missing in output of bands.x in case of ibrav=7

[Andrea Dal Corso]

I don't think this is an error. The routine writes the coordinates of
the points when 
a) the path changes direction or
b) the small point group of k changes

None of the above occurs at N along the path gS-N-gS1, so the code
assumes this is one line gS-gS1, not two.
It is the same thing for an fcc lattice at the K point along the path 
gG-K (3/4,3/4,0) -X (1,1,0). K is not considered a high symmetry point
and only one line from gG to X is found, not two.
In the second case for the path gG-N-gS at N there is a change of the
path direction and the point is written on output.

HTH,

Andrea

On Wed, 2017-05-17 at 09:45 +0800, balabi wrote: 
> Dear developers:
>     I am using QE6.1 and calculating TaAs right now. TaAs belongs to
> ibrav 7. According to "Points inside the Brillouin zone" pdf. I
> choosed gG-gS-N-gS1 path. But I found the output of bands.x contains
> only three high-symmetry points. The N point is missing
> 
> 
> high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000
> high-symmetry point:  0.5435 0.0000 0.0000   x coordinate   0.5435
> high-symmetry point:  0.4565 0.0000 0.2951   x coordinate   0.8512
> 
> 
> 
> 
> I tried several cases, and found as soon as I put gS right before N,
> the high-symmetry point number is wrong. For example, gG-N-gS-gS1 will
> give 4 symmetry point correctly.
> 
> 
> high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000
> high-symmetry point:  0.5000 0.0000 0.1475   x coordinate   0.5213
> high-symmetry point:  0.5435 0.0000 0.0000   x coordinate   0.6751
> high-symmetry point:  0.4565 0.0000 0.2951   x coordinate   0.9828
> 
> 
> below is my scf file
> ---------------------------------
> 
> 
> 
> &CONTROL
> prefix='TaAs',
> calculation='bands',
> restart_mode='from_scratch',
> wf_collect=.true.,
> verbosity='high',
> outdir='./qe_tmpdir',
> pseudo_dir='./pseudo',
> /
> &SYSTEM
>     ibrav = 7,celldm(1) =
> 6.490830825570885,celldm(3)=3.389134738558286,nat = 4,ntyp = 2,
>     ecutwfc = 50,ecutrho = 450,
> /
> &ELECTRONS
>     conv_thr = 1.0d-10,  
> /
> ATOMIC_SPECIES
> Ta    180.94788    Ta.pbe-spn-kjpaw_psl.0.2.UPF
> As     74.921595      As.pbe-n-kjpaw_psl.0.2.UPF
> ATOMIC_POSITIONS crystal
> As     0.5000    0.1670    0.6670
> As     0.0000    0.4170    0.4170
> Ta    0.5000    0.7500    0.2500
> Ta    0.0000    0.0000    0.0000
> K_POINTS tpiba_b
> 4
> gG 6 
> gS 6 
> N 6 
> gS1 1
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-- 
Andrea Dal Corso                    Tel. 0039-040-3787428
SISSA, Via Bonomea 265              Fax. 0039-040-3787249
I-34136 Trieste (Italy)             e-mail: dalcorso at sissa.it