[Pw_forum] A little energy gap (~ 0.2 eV) for graphene

Cao TF tfcao at theory.issp.ac.cn
Mon May 21 14:13:54 CEST 2012


Dear QE users,
  I have calculated the density of states (DOS) of pure graphene.  The supercell used in my work  is a rectangular cell containing 60 carbon atoms.   But something has puzzled me greatly. There is always a little energy gap (~0.2 eV) in the DOS, which contracts with the fact that graphene is zero gap semiconductor. Although I have change many parameters. This problem has not been solved. Here I give the input file and I will be greatly appreciated if you can give me some suggestions.
For scf.in                                                                                     
&CONTROL
     title = 'graphene layer' ,
     calculation = 'scf' ,
     restart_mode = 'from_scratch' ,
     outdir = './tmp' ,
     pseudo_dir = '~pseudo' ,
     prefix = 'graphene' ,
 /
 &SYSTEM
     ibrav = 8 ,
     a = 12.31 , b = 12.79312342 , c = 12.000 ,
     nat = 60 ,
     ntyp = 1 ,
     occupations = 'smearing' ,
     tot_charge = 0.0,
     degauss = 0.02 ,
     smearing = 'mp' ,
     nspin = 2 ,
     starting_magnetization(1) = 0.5 ,
     ecutwfc = 30.0 ,
     ecutrho = 300.0 ,
 /
 &ELECTRONS
     conv_thr = 1.0d-8 ,
     mixing_mode = 'local-TF' ,
     mixing_beta = 0.7 ,
     diagonalization = 'david' ,
 /
ATOMIC_SPECIES
  C   12.0107  C.pbe-rrkjus.UPF
ATOMIC_POSITIONS crystal
 C   0.0000000       0.0000000      0.50000000
 C  0.10000000      5.55555671E-02  0.50000000
 C  0.10000000      0.16666667      0.50000000
 C   0.0000000      0.22222224      0.50000000
 C   0.0000000      0.33333334      0.50000000
 C  0.10000000      0.38888890      0.50000000
 C  0.10000000      0.50000000      0.50000000
 C   0.0000000      0.55555558      0.50000000
 C   0.0000000      0.66666669      0.50000000
 C  0.10000000      0.72222227      0.50000000
 C  0.10000000      0.83333337      0.50000000
 C   0.0000000      0.88888896      0.50000000
 C  0.20000000       0.0000000      0.50000000
 C  0.30000001      5.55555671E-02  0.50000000
 C  0.30000001      0.16666667      0.50000000
 C  0.20000000      0.22222224      0.50000000
 C  0.20000000      0.33333334      0.50000000
 C  0.30000001      0.38888890      0.50000000
 C  0.30000001      0.50000000      0.50000000
 C  0.20000000      0.55555558      0.50000000
 C  0.20000000      0.66666669      0.50000000
 C  0.30000001      0.72222227      0.50000000
 C  0.30000001      0.83333337      0.50000000
 C  0.20000000      0.88888896      0.50000000
 C  0.40000001       0.0000000      0.50000000
 C  0.50000000      5.55555671E-02  0.50000000
 C  0.50000000      0.16666667      0.50000000
 C  0.40000001      0.22222224      0.50000000
 C  0.40000001      0.33333334      0.50000000
 C  0.50000000      0.38888890      0.50000000
 C  0.50000000      0.50000000      0.50000000
 C  0.40000001      0.55555558      0.50000000
 C  0.40000001      0.66666669      0.50000000
 C  0.50000000      0.72222227      0.50000000
 C  0.50000000      0.83333337      0.50000000
 C  0.40000001      0.88888896      0.50000000
 C  0.60000002       0.0000000      0.50000000
 C  0.70000005      5.55555671E-02  0.50000000
 C  0.70000005      0.16666667      0.50000000
 C  0.60000002      0.22222224      0.50000000
 C  0.60000002      0.33333334      0.50000000
 C  0.70000005      0.38888890      0.50000000
 C  0.70000005      0.50000000      0.50000000
 C  0.60000002      0.55555558      0.50000000
 C  0.60000002      0.66666669      0.50000000
   C  0.70000005      0.72222227      0.50000000
 C  0.70000005      0.83333337      0.50000000
 C  0.60000002      0.88888896      0.50000000
 C  0.80000001       0.0000000      0.50000000
 C  0.90000004      5.55555671E-02  0.50000000
 C  0.90000004      0.16666667      0.50000000
 C  0.80000001      0.22222224      0.50000000
 C  0.80000001      0.33333334      0.50000000
 C  0.90000004      0.38888890      0.50000000
 C  0.90000004      0.50000000      0.50000000
 C  0.80000001      0.55555558      0.50000000
 C  0.80000001      0.66666669      0.50000000
 C  0.90000004      0.72222227      0.50000000
 C  0.90000004      0.83333337      0.50000000
 C  0.80000001      0.88888896      0.50000000
 K_POINTS automatic
 8 8 1 0 0 0
For  nscf.in  
&CONTROL
     title = 'graphene layer' ,
     calculation = 'nscf' ,
     restart_mode = 'from_scratch' ,
     outdir = './tmp' ,
     pseudo_dir = '/lustre/ISSP2/tfcao/pseudo' ,
     prefix = 'graphene' ,
 /
 &SYSTEM
     ibrav = 8 ,
     a = 12.31 , b = 12.79312342 , c = 12.000 ,
     nat = 60 ,
     ntyp = 1 ,
     occupations = 'tetrahedra' ,
     tot_charge = 0.0,
     nspin = 2 ,
     starting_magnetization(1) = 0.5 ,
     ecutwfc = 30.0 ,
     ecutrho = 300.0 ,
 /
 &ELECTRONS
     conv_thr = 1.0d-8 ,
     mixing_mode = 'local-TF' ,
     mixing_beta = 0.7 ,
     diagonalization = 'david' ,
 /
ATOMIC_SPECIES
  C   12.0107  C.pbe-rrkjus.UPF
For dos.in 
 &inputpp
  prefix = 'graphene' ,
  outdir = './tmp' ,
  Emin = -4.0 ,
  Emax = 4.0 ,
  DeltaE = 0.01 ,
  fildos = graphene.dos ,
/
The accessory is the DOS I have got.                                                            
I  am sorry for such a long file. I hope that you can give some suggestions.  
======================================================================
Tengfei Cao,   Research Laboratory for Computational Materials Sciences,
Instutue of Solid State Physics,the Chinese Academy of Sciences,

======================================================================






                                                                                                                                                                                                                                                                          93,2         底端
                                                                                                                                                                                                                                                                       1,2          顶端


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20120521/17eee2aa/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: graphene.dos
Type: application/octet-stream
Size: 35291 bytes
Desc: not available
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20120521/17eee2aa/attachment.obj>


More information about the users mailing list