[Pw_forum] band structure issue

[Tariq Sami]

Hello dear QE users, 
   I'm using Quantum espresso-5.2.0 for the calculation of band structure of rutile TiO2. While doing my calculations for single cell using


&control
    calculation = 'scf',
    prefix = 'tio',
    verbosity = 'default',
    outdir = './' ,
    pseudo_dir = '/home/sami_QU/espresso-5.2.0/pseudo',

 /
  &system
    ibrav = 6,
    celldm(1) = 8.680890966,
    celldm(3) = 0.64394729330137,
    nat =  6,
    ntyp = 2,
    ecutwfc = 40,
    ecutrho = 300,
    occupations = 'tetrahedra',
    smearing ='mp',
    degauss= 0.02 ,
  /
  &electrons
    conv_thr = 1.0e-09,
    electron_maxstep = 100,
    mixing_beta = 0.3,
    conv_thr = 1.0e-08,
    mixing_mode = 'plain',
  /

 ATOMIC_SPECIES
  O 15.999   O.pz-nc.UPF
  Ti 47.867 Ti.pz-n-nc.UPF
 ATOMIC_POSITIONS (alat)
 Ti  0.00000000  0.00000000  0.00000000
Ti  0.50000000  0.50000000  0.32197370
 O   0.30530000  0.30530000  0.00000000
 O  -0.30530000 -0.30530000  0.00000000
 O   0.80530010  0.19470000  0.32197370
 O   0.19470000  0.80530010  0.32192370
 K_POINTS (automatic)
  3 3 6 1 1 1
my results are some what consistent with the previous studies ,but when i do the same calculations for 2x2x2 supercell using   
    / 
&system
    ibrav = 6,
    celldm(1) = 17.36178193,
    celldm(3) = 0.64394729330137,
    nat =  48,
    ntyp = 2,
    ecutwfc = 40,
    ecutrho = 300,
    occupations = 'tetrahedra',
    smearing ='mp',
    degauss= 0.02 ,
  /
  &electrons
    conv_thr = 1.0e-09,
    electron_maxstep = 100,
    mixing_beta = 0.3,
    conv_thr = 1.0e-08,
    mixing_mode = 'plain',
  /

 ATOMIC_SPECIES
  O 15.999  O.pz-nc.UPF
  Ti 47.867 Ti.pz-n-nc.UPF
 ATOMIC_POSITIONS (alat)
 Ti  0.00000000  0.00000000  0.00000000
 Ti  0.25000000  0.25000000  0.16098685
 O   0.15265000  0.15265000  0.00000000
 O  -0.15265000 -0.15265000  0.00000000
 O   0.40265005  0.09735000  0.16986850
 O   0.09735000  0.40265005  0.16986850
 Ti  0.50000000  0.00000000  0.00000000
 Ti  0.75000000  0.25000000  0.16098685
 O   0.65265000  0.15265000  0.00000000
 O   0.34735000 -0.15265000  0.00000000
 O   0.90265005  0.09735000  0.16986850
 O   0.59735000  0.40265005  0.16986850
 Ti  0.00000000  0.50000000  0.00000000
 Ti  0.25000000  0.75000000  0.16098685
 O   0.15265000  0.65265000  0.00000000
 O  -0.15265000  0.34735000  0.00000000
 O   0.40265005  0.59735000  0.16986850
 O   0.09735000  0.90265005  0.16986850
 Ti  0.50000000  0.50000000  0.00000000
 Ti  0.75000000  0.75000000  0.16098685
 O   0.65265000  0.65265000  0.00000000
 O   0.34735000  0.34735000  0.00000000
 O   0.90265005  0.59735000  0.16986850
 O   0.59735000  0.90265005  0.16986850
 Ti  0.00000000  0.00000000  0.32197370
 Ti  0.25000000  0.25000000  0.48296055
 O   0.15265000  0.15265000  0.32197370
 O  -0.15265000 -0.15265000  0.32197370
 O   0.40265005  0.09735000  0.48296055
 O   0.09735000  0.40265005  0.48296055
 Ti  0.50000000  0.00000000  0.32197370
 Ti  0.75000000  0.25000000  0.48296055
 O   0.65265000  0.15265000  0.32197370
 O   0.34735000 -0.15265000  0.32197370
 O   0.90265005  0.09735000  0.48296055
 O   0.59735000  0.40265005  0.48296055
 Ti  0.00000000  0.50000000  0.32197370
 Ti  0.25000000  0.75000000  0.48296055
 O   0.15265000  0.65265000  0.32197370
 O  -0.15265000  0.34735000  0.32197370
 O   0.40265005  0.59735000  0.48296055
 O   0.09735000  0.90265005  0.48296055
 Ti  0.50000000  0.50000000  0.32197370
 Ti  0.75000000  0.75000000  0.48296055
 O   0.65265000  0.65265000  0.32197370
 O   0.34735000  0.34735000  0.32197370
 O   0.90265005  0.59735000  0.48296055
 O   0.59735000  0.90265005  0.48296055

 K_POINTS (automatic)
  3 3 6 1 1 1
  

there are some extra states , as in Fig[1]. The same test calculations when done using siesta gives accurate results Fig. [2].A comparison of Dos of the cell and supercell using siesta and Qe respectively is shown in the Fig[3]. Actually i'm a new QE user , so can anyone please help me out in this regard
I look forward to your suggestion! Thank you! 
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