[Pw_forum] matdyn.x warning message

[Eyvaz Isaev]

Dear Mikiyas,

> Z* not found in file graphene.fc, TO-LO splitting at q=0
> will be absent
> A direction for q was not specified: TO-LO splitting will
> be absent

The first message is just stating that you consider graphene as a metallic system for which there is no LO-TO splitting, of course.

The second message: may be your q-path does not contain Gamma point. Anyway, it is harmless in your (metallic) case

If you send me your fc-file and  q-path,  I will try to have a look at.

 >      ecutrho = 480.0,
You do not need such high ecutrho as you use norm-conserving PsP.
Use default value (4*ecutwfc).

By the way, did you specify zasr in q2r.in and matdyin.in files?

Bests,
Eyvaz. 

-------------------------------------------------------------------
Prof. Eyvaz Isaev, 
Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, 
Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden 
Condensed Matter Theory Group, Uppsala University, Sweden 
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com


--- On Thu, 8/20/09, Mikiyas Tsegaye <mastermik at gmail.com> wrote:

 
> 
> I'm trying to plot the phonon dispersion of graphene. I
> have done the  
> dispersions for Silicon, and Germanium, and also for
> Diamond. All of  
> which worked out well. Graphene, however, is giving me the
> following  
> error in the second-to-last matdyn.x step:
> 
> --------------------------------------------------------------------
> message from routine matdyn
> 
> Z* not found in file graphene.fc, TO-LO splitting at q=0
> will be absent
> A direction for q was not specified: TO-LO splitting will
> be absent
> 
> --------------------------------------------------------------------
> 
> The dispersion that it then produces looks very jagged and
> the numbers  
> are off. For examples, the acoustic modes don't go to zero
> at the  
> gamma point, and the acoustic and optical branches don't
> touch at the  
> K-point like they're supposed to. I would really appreciate
> any help  
> on this matter. My input file is as follows:
> 
> -----------------------------------------------
> # SCF step
> 
>   &control
>      calculation='scf',
>      restart_mode='from_scratch',
>      prefix='graph',
>      tstress=.true.,
>      tprnfor=.true.,
>      pseudo_dir = '$PSEUDO_DIR/',
>      outdir='$TMP_DIR/'
>   /
>   &system
>      ibrav = 0, nat=2, ntyp= 1,
>      ecutwfc = 40.0,
>      ecutrho = 480.0,
>      occupations = 'smearing',
>      smearing = 'gaussian',
>      degauss = 0.02,
>   /
>   &electrons
>      diagonalization = 'cg',
>      conv_thr =  1.0d-6
>   /
> CELL_PARAMETERS {hexagonal}
> 4.02  2.321  0.00
> 4.02 -2.321  0.00
> 0.00  0.00   69.75
> ATOMIC_SPECIES
> C 12.01 C.pz-vbc.UPF
> ATOMIC_POSITIONS {bohr}
> C  0.0  0.0  0.0
> C  2.68 0.0  0.0
> K_POINTS automatic
> 16 16 1 0 0 0
> 
> $PW_COMMAND < graphene.scf.in > graphene.scf.out
> 
> # calculate phonons
> 
> phonons of graphene
> &INPUTPH
>   amass(1) = 12.01,
>   outdir = '$TMP_DIR/',
>   prefix = 'graph',
>   tr2_ph = 1.0d-12,
>   fildyn = 'graph.dyn',
>   fildrho = 'graph.rho',
>   ldisp = .true.,
>   lnscf = .true.,
>   nq1 = 16,
>   nq2 = 16,
>   nq3 = 1
>  
> -------------------------------------------------------
> 
> Am I missing something in my inputs?
> 
> thank you!
> 
> - Mikiyas Tsegaye
> University of Virginia, ECE
> Charlottesville, VA, USA
> mst3c at virginia.edu
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