[Pw_forum] graphene phonon dispersion

[yhho]

Dear all,
I have tried many different way as I saw on pw_forum 
but I still can't get a good result which is similar to tthe figure from paper I found. 
In this figure, red line is what I got and gray line is from reference 

ref: Physics ReportsVolume 409, Issue 2, March 2005, Pages 47-99
http://imageshack.us/photo/my-images/853/c2phdosvc1.jpg/

I also found another paper shows a little different phonon dispersion figure of graphite:
red line is my result and gray line is from reference 
ref: 10.1103/PhysRevLett.92.075501
http://imageshack.us/photo/my-images/851/c2phdosvc3.jpg/

I have no idea to improve this 
because I have tried vc-relax and relax and the structure didn't change a lot due to that.
And I also tried increasing q-points, there's no much different from the fewer q-points results.
Please give me some suggestion. Thanks very much.

input file
(scf.in)
 &control
    calculation ='scf'
    restart_mode ='from_scratch'
    pseudo_dir ='/lustre/lwork/dyyang/bin/espresso-4.0.3/pseudo/'
    outdir ='./'
    prefix ='AuC'
 /
 &system
    ibrav =0
    celldm(1)=  4.6514
    nat =  2 ,
    ntyp =  1 ,
    ecutwfc = 24.0,
    ecutrho =  240.0,
    occupations ='smearing',
    degauss= 0.02
 /
 &electrons
    diagonalization= 'david'
    conv_thr =   1.0d-12
    mixing_beta =  0.7
 /
ATOMIC_SPECIES
  C 12.0107 C.pz-rrkjus.UPF
CELL_PARAMETERS (alat)
   0.984533834   0.000000000   0.000000000
  -0.492266917   0.852631311   0.000000000
   0.000000000   0.000000000   5.328569075
ATOMIC_POSITIONS {crystal}
C        0.481112321   1.128944752   0.517391300
C        0.814471461   0.795556146   0.517391309
K_POINTS
 7
   0.0000000   0.0000000   0.0000000  0.1250000
   0.0000000   0.2932100   0.0000000  0.2500000
   0.0000000  -0.5864199   0.0000000  0.1250000
   0.2539273   0.1466050   0.0000000  0.5000000
   0.2539273   0.4398150   0.0000000  0.5000000
  -0.5078546  -0.2932100   0.0000000  0.2500000
  -0.5078546   0.0000000   0.0000000  0.2500000


(ph.in)
phonons of AuC
 &inputph
  tr2_ph=1.0d-12,
  ldisp=.true.,
  nq1=4, nq2=4, nq3=1
  amass(1)= 12.0107
  prefix='AuC',
  outdir='./'
  fildyn='AuC.dyn',
 /


--
Yu-Han Ho
Research Assistant
Institute of Atomic and Molecular Sciences(IAMS), lab503
No. 1, Roosevelt Rd., Sec. 4, Taipei, 10617, Taiwan
Tel: 886-2-2362-0212

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