[Pw_forum] Graphene Phonons Not Working

[stefano de gironcoli]

Dear Abualnaja ,

    how did you chose the smearing and k-point combination ?
    your degauss (0.1 Ry =1.36 eV) looks huge to me, while your k-point 
grid looks very dense.
    mp smearing is a good choice for *real* metals (with a significant 
dos(e_F)) even if someone would favor mv smearing. I think that in the 
case of graphene with vanishing dos(e_F) the simpler gaussian broadening 
should be fine and possibly preferable.

stefano


On 21/04/2016 20:32, Abualnaja, Faris wrote:
>
> Apologies all in the q2r and matdyn files zasr and asr should both be 
> 'simple' and NOT 'crystal'
>
>
>
> ------------------------------------------------------------------------
> *From:* pw_forum-bounces at pwscf.org <pw_forum-bounces at pwscf.org> on 
> behalf of Abualnaja, Faris <f.abualnaja15 at imperial.ac.uk>
> *Sent:* 21 April 2016 16:42
> *To:* pw_forum at pwscf.org
> *Subject:* [Pw_forum] Graphene Phonons Not Working
>
> To whom it may concern,
>
>
> I've been having trouble lately trying to produce graphene phonon 
> dispersion plots. I am currently using quantum-espresso/5.0.2. I ran 
> an scf calculation using an LDA norm conserving pseudo potential 
> (C.pz-vbc.UPF). I found an optimised lattice parameter of 4.698 (Bohr) 
> using a vc-relax calculation. I then ran an scf with the optimised 
> lattice parameter and ecutwfc. I then proceeded onto producing a band 
> structure with the following k-points in units of 2pi/a (Gamma (0,0,0) 
> - K (0.33333, 0.57735027, 0) - M (0.5, 0.28867513, 0)). The band 
> structure agrees with literature, where the dirac points meet at the K 
> point. I then moved on to calculating the phonon at each k (or 
> q) point. I ran the scf calculation once again in a new directory, I 
> ran the phonon at gamma, K, and M. the results seemed to agree 
> with literature. However, when I ran the phonon dispersion 
> calculation, the results go all over the place. The gamma k and m 
> points are the same but the curve is not expected. Obviously, after 
> running the ph.x I ran a q2r.x calculation, followed by a matdyn.x 
> calculation. To be clear I checked my k-points, I checked the k-path, 
> the mp grid I used was 12x12x1 when calculating the phonon 
> dispersion and 48x48x1 when running an scf calculation. Also, to 
> clarify I did the tutorial for Al and Si and produced correct 
> plots. Below are my input files:
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> -------- SCF 
> ---------------------------------------------------------------------------------------------------------------------
>
> &CONTROL
>
>   prefix         = 'graphene'
>
>   pseudo_dir     = '/home/fa2215/bin/upf_files'
>
>   calculation    = 'scf'
>
>   restart_mode   = 'from_scratch'
>
>   verbosity      = 'high'
>
>   tprnfor        = .TRUE.
>
>   tstress        = .TRUE.
>
>   etot_conv_thr  = 1.0D-4
>
>   forc_conv_thr  = 1.0D-3
>
>   nstep          = 50000
>
>   wf_collect     = .TRUE.
>
> /
>
>
> &SYSTEM
>
>   ibrav            = 4
>
>   celldm(1)        = 4.698
>
>   celldm(3)        = 18.616
>
>   nat              = 2
>
>   ntyp             = 1
>
>   nbnd             = 10
>
>   ecutwfc          = 110
>
>   ecutrho          = 440
>
>   occupations      = 'smearing'
>
>   smearing         = 'mp'
>
>   degauss          = 0.1
>
> /
>
>
> &ELECTRONS
>
>   diagonalization   = 'david'
>
>   electron_maxstep  = 1000
>
>   conv_thr          = 1.0e-8
>
>   mixing_beta       = 0.3
>
> /
>
>
> ATOMIC_SPECIES
>
>   C 12.01 C.pz-vbc.UPF
>
> ATOMIC_POSITIONS crystal
>
>   C         0.6666666666 0.3333333333  0.0000000000
>
>   C         0.3333333333 0.6666666666  0.0000000000
>
> K_POINTS (automatic)
>
> 48 48 1  0 0 0
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------ PHONON ---------------------------------------------------------------------------------------------------------------------
>
> Phonon Dispersion of graphene
>
>  &inputph
>
>   tr2_ph=1.0d-12
>
>   ldisp=.true.
>
>   nq1=12 nq2=12 nq3=1
>
>   prefix='graphene'
>
>   amass(1)=12.01
>
> outdir='/work/fa2215/Computational_Data/Graphene/Flat_Graphene/NM_PZ_LDA/Phonon_Calc/Disp/Disp2'
>
>   fildyn='graphene.dyn'
>
>  /
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ----------- Q2R --------------------------------------------------------------------------------------------------------------------
>
> &input
>
>     fildyn='graphene.dyn', zasr='crystal', flfrc='graphene.fc'
>
> /
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
> -------- MATDYN -------------------------------------------------------------------------------------------------------------------
>
> &input
>
>     asr='crystal'
>
>     amass(1)=12.01
>
>     flfrc='graphene.fc'
>
>     flfrq='graphene.freq'
>
> /
>
>  219
>
>     0.000000    0.000000    0.000000   1.0
>
>          : :                    :                :
>
> ------------------------------------------------------------------------------------------------------------------------------------
>
>
> So to recap my procedure was as follows:
>
>
> scf
>
> phonon disp
>
> q2r
>
> matdyn
>
>
> Let me know if anything is unclear and thank you for your help!
>
>
> Best,
>
>
> Faris
>
>
>
>
>
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