[QE-users] Problem with the order of introducing atoms

[Mohammad Alidoosti]

Dear all


I am doing the  SCF calculations of hexagonal InSe using QE 6.2.1, which
consist of four atoms (2In+2Se). When I changed the order of introducing
atoms in the atomic position block in my input file, I saw that the number
of selected k-points in the output changed from 52 to 14. That is, the code
can find the symmetry group in one case but no symmetry in the other case.
Is it important the order of introducing atoms!!!!! while I have done the
same calculations for both of them. It should be noted that I got the same
problem in other versions of QE such as 5.4 and 6.3. In the following, you
can find the input files.

The first case :
&control
    calculation="scf"
    restart_mode="from_scratch",
    prefix='Inse',
    pseudo_dir = '/home/pseudo',
    outdir='./tmp'
 /
 &system
    ibrav=  0, nat= 4, ntyp= 2,
    ecutwfc =80,
 /
 &electrons
    conv_thr =  1.0d-6
    mixing_beta = 0.6
/
ATOMIC_SPECIES
In  114.818  In.pbe-hgh.UPF
Se  78.96    Se.pbe-hgh.UPF
ATOMIC_POSITIONS (crystal)
  Se      0.33332800000000   0.66666100000000   0.06148300000000
  Se      0.33332800000000   0.66666100000000   0.27424600000000
  In      0.66666200000000   0.33332900000000   0.11202500000000
  In      0.66666200000000   0.33332900000000   0.22371100000000
CELL_PARAMETERS (angstrom)
   2.04502258622038  -3.54208302195961   0.00000000000000
   2.04502258622038   3.54208302195961   0.00000000000000
   0.00000000000000   0.00000000000000  25.00000000076542
K_POINTS {automatic}
 10 10 1  0 0 0

###############################################

In the second case, ATOMIC_POSITIONS should be changed to :
ATOMIC_POSITIONS (crystal)
  In      0.66666200000000   0.33332900000000   0.11202500000000
  In      0.66666200000000   0.33332900000000   0.22371100000000
  Se      0.33332800000000   0.66666100000000   0.06148300000000
  Se      0.33332800000000   0.66666100000000   0.27424600000000


Thanks in advance.
-- 
Institute for Research in Fundamental Sciences (IPM)
School of Nano-Science
Shahid Farbin Alley
Shahid Lavasani st
P.Code: 19538-33511
Tehran, Iran
Tel: +98 21 2310 -3070
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