[Pw_forum] Phonon dispersion - negative frequencies

[Sohail Ahmad]

Dear QE usersI wish to calculate the phonon dispersion curve for monolayer Transition metal dichalcogenides.I am also getting negative frequencies (upto -4 eV) despite taking convergence upto  tr2_ph = 10^-15 
 as suggested on forum earlier.Can any body comment on my input so as i could improve my result
Best Wishes
SohailKing khalid UniversityAbha, Saudi Arabia
-------------------------
&control
  calculation = 'scf',
  restart_mode = 'from_scratch',
  prefix = 'ZrS2m',
  pseudo_dir = '/home/sohail/soft/espresso-4.3.2/espresso-4.3.2/pseudo',
  outdir = './OUT',
  nstep = 500,
  verbosity = 'high',
/
&system
  ibrav = 4, a = 3.75, b = 3.75, c = 15.0,
  nat = 3, ntyp = 2,
  ecutwfc = 75,
  ecutrho = 300,
  nbnd = 15,
  occupations = 'fixed',
/
&electrons
  mixing_beta = 0.7,
  conv_thr = 1.0d-14,
/
ATOMIC_SPECIES
Zr  91.22  Zr.pbe-mt_fhi.UPF
S   32.06  S.pbe-mt_fhi.UPF
ATOMIC_POSITIONS {Angstrom}
Zr  0.000000000  0.000000000  0.000000000
S  -0.000000018  2.113679346  1.383970000
S   1.830500018  1.056839657 -1.383970000
K_POINTS AUTOMATIC
4 4 1 1 1 1
&inputph
 tr2_ph = 1.0d-15,
 ldisp = .true.,
 nq1 = 4, nq2 = 4, nq3 = 1,
 amass(1) = 91.22,
 amass(2) = 32.06,
 prefix = 'ZrS2m',
 outdir = './OUT',
fildyn = 'ZrS2m.dyn',
/

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