[Pw_forum] negative frequency

[partha sarathi ghosh]

Dear all,
             I am trying to do phonon calculation of bcc-Zr from (0,0,0) to
(1,1,1) in q-space.But I am getting negative frequencies in several
q-points, also my curve is very different from experimental one. I optimized
the system w.r.t ecutwf, ecutrho ,conv_thr, k-point sampling .I also tried
the same calculation by changing potential also.I am new fellow in this
field so I am unable to understand what is happening wrong !!
My input files are :
1) zr.scf.in
 &control
    calculation='scf'
    restart_mode='from_scratch',
    tstress = .true.
    tprnfor = .true.
    prefix='zr',
    pseudo_dir = '/home/general/Desktop/espresso-4.0.5/pseudo/',
    outdir='./'
 /
 &system
    ibrav=  0, celldm(1) =6.7, nat=  1, ntyp= 1,
    degauss=0.04,
    smearing='mp',
    occupations='smearing',
    ecutwfc =35.0
    ecutrho = 350.0
 /
 &electrons
    conv_thr =  1.0d-8
    mixing_beta = 0.7
 /
ATOMIC_SPECIES
 Zr  91.22  Zr.pbe-nsp-van.UPF
ATOMIC_POSITIONS
Zr 0.00 0.00 0.00
K_POINTS  AUTOMATIC
 16 16 16  0 0 0
CELL_PARAMETERS { cubic }
  -0.500000000000000   0.500000000000000   0.500000000000000
   0.500000000000000  -0.500000000000000   0.500000000000000
   0.500000000000000   0.500000000000000  -0.500000000000000
 ##########################################
2) zr.ph.in
phonons of Zr
 &inputph
  tr2_ph=1.0d-10,
  prefix='zr',
  ldisp=.true.,
  nq1=8, nq2=8, nq3=8
  amass(1)=91.22,
  outdir='./',
  fildyn='zr.dyn',
 /
Any one can help me please .
Thanks in advance.
P S Ghosh
B.A.R.C.
India
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