[Pw_forum] matdyn.x warning message

[Mikiyas Tsegaye]

Dear Friends,

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