[Pw_forum] high-symmetry point is wrong in the output of bands.x

[Giovanni Pizzi]

Hi,
I think both values are correct, depending on which units one is referring to.

X is (1/2,/1/2,0) (and equivalent) in *scaled* coordinates in the *primitive* cell,
But is along {1,0,0} when expressed in cartesian coordinates, or w.r.t. the *conventional* cell.

The value printed by bands.x is consistent with the units/choices of the code.

Best,

Giovanni

P.S.: You can see an interactive 3D visualisation of the BZ at http://materialscloud.org/tools/seekpath
(Choose the example "cF2 [with inversion]” for this specific case).



--
Giovanni Pizzi
Theory and Simulation of Materials and MARVEL, EPFL
http://people.epfl.ch/giovanni.pizzi
http://nccr-marvel.ch/en/people/profile/giovanni-pizzi

On 13 Apr 2017, at 10:41, Paolo Giannozzi <p.giannozzi at gmail.com<mailto:p.giannozzi at gmail.com>> wrote:

On Thu, Apr 13, 2017 at 3:11 AM, balabi <balabi at qq.com<mailto:balabi at qq.com>> wrote:

I am using QE6.1. I found the high symmetry point in the output of bands.x
is not right.

sure? your system has a FCC lattice (ibrav=2). Find a picture of the
Brillouin Zone and of high-symmetry points, for instance this one:
http://www.iue.tuwien.ac.at/phd/dhar/node18.html
Where do you see that X is (1/2, 1/2, 0) ?

Paolo

Take copper as an example, set k path as below in bands calcuation

K_POINTS tpiba_b
2
gG 20
X 1

a possible X coordinate should be "0.5 0.5 0". However, the output of
bands.x is

high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000
high-symmetry point:  0.0000 1.0000 0.0000   x coordinate   1.0000

"0 1 0" is definitely not right for X point.

The reason I want to use high symmetry point information is that I want to
write an automatic k path transformation tool from PW to wannier90 input win
file.

below are input files for test
---------------------------------------
copper.scf.in
----------------------------------
&control
   calculation='scf'
   restart_mode='from_scratch',
pseudo_dir = '/mnt/e/DFT_code/QE/pseudo',
   outdir='./'
   prefix='cu'
/
&system
   ibrav = 2, celldm(1) =6.822, nat= 1, ntyp= 1,
   ecutwfc = 30.0
   occupations='smearing', smearing='cold', degauss=0.02
/
&electrons
/
ATOMIC_SPECIES
Cu 63.546 Cu.pz-n-van_ak.UPF
ATOMIC_POSITIONS
Cu 0.0 0.0 0.0
K_POINTS (automatic)
8 8 8 0 0 0
----------------------------------------------
copper.bands.in
-------------------------------------------
&control
   calculation='bands'
   restart_mode='from_scratch',
pseudo_dir = '/mnt/e/DFT_code/QE/pseudo',
   outdir='./'
   prefix='cu'
/
&system
   ibrav = 2, celldm(1) =6.822, nat= 1, ntyp= 1,
   ecutwfc = 30.0
   occupations='smearing', smearing='cold', degauss=0.02
   nbnd=12
/
&electrons
/
ATOMIC_SPECIES
Cu 55.85 Cu.pz-n-van_ak.UPF
ATOMIC_POSITIONS
Cu 0.0 0.0 0.0
K_POINTS tpiba_b
2
gG 20
X 1
----------------------------------
bands.x.in
--------------------------------
&bands
outdir='./',
prefix='cu',
filband='bands.dat',
/

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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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