[Pw_forum] phonon calculation

Fri May 2 10:39:28 CEST 2014

Dear All,
    I am trying to calculate IR frequency of NH4Br crystal. In ph.in and
dynmat.in I have used asr=.true., and asr='zero-dim' respectively. So, I
should get 6 zero frequency due to asr option. But I am getting the
following frequencies

-----------------------------------------------------
# mode   [cm-1]    [THz]      IR
    1   -265.41   -7.9566    8.4124
    2   -251.33   -7.5346    8.3177
    3   -224.98   -6.7446    1.1717
    4   -108.27   -3.2458    0.0181
    5     -0.00   -0.0000    0.0000
    6     -0.00   -0.0000    0.0000
    7     -0.00   -0.0000    0.0000
    8      0.00    0.0000    0.0000
    9      0.00    0.0000    0.0000
   10      0.00    0.0000    0.0000
   11    192.15    5.7604    0.0005
   12    238.67    7.1553    0.4008
   13    264.00    7.9144    3.5942
   14    293.57    8.8012    0.6786
   15    329.56    9.8799    1.7381
   16    392.07   11.7539    0.0041
   17    409.82   12.2862    0.0005
   18    413.05   12.3828    0.0013
   19   1088.47   32.6315    1.3513
   20   1285.27   38.5313    2.2625
   21   1393.04   41.7624    1.9338
   22   1433.41   42.9725    3.7008
   23   1476.19   44.2550    1.3273
   24   1493.99   44.7888    1.1527
   25   1597.18   47.8821    0.6625
   26   1635.26   49.0238    0.0000
   27   1676.34   50.2554    0.0047
   28   1686.18   50.5505    0.0000
   29   2657.92   79.6825   28.6572
   30   2931.08   87.8715   14.0421
   31   3056.17   91.6215    0.2991
   32   3078.70   92.2970   18.7792
   33   3094.15   92.7603    7.0421
   34   3148.71   94.3958   61.3242
   35   3176.09   95.2167   69.5553
   36   3474.05  104.1493   36.0143
-----------------------------------------------------------------------------------------------

I am also giving my inputs also
-----------------------------------
scf.in
&control
    calculation = 'scf',
    title = 'NH4Br'
    restart_mode = 'from_scratch'
    tprnfor = .TRUE.
    prefix = 'NH4Br',
    outdir = '------'
    pseudo_dir = '---------'
    nstep=1000
 /
 &system
    ibrav = 0,
     nat = 12,
    ntyp = 3,
    nbnd = 60
    tot_charge = 0
   celldm(1) = 1.890359168
    ecutwfc = 30.00
    ecutrho = 300.00
    london      = .true.
    london_s6   = 0.75
    london_rcut = 200.00
 /
 &electrons
 electron_maxstep = 1000
  mixing_beta=0.3
  conv_thr = 1.0d-8
 diagonalization='david'
  diago_david_ndim = 4
/
 &CELL
   cell_dynamics='bfgs'
   press = 0.0
 /
ATOMIC_SPECIES
    H    1.00794   H.pbe-van_ak.UPF
    Br   79.904   Br.pbe-van_mit.UPF
    N    14.0067   N.pbe-van_ak.UPF
ATOMIC_POSITIONS angstrom
N        0.000000000   0.000000000   0.000000000
.
.
H        0.000000000   4.781723484   3.381166715
K_POINTS automatic
6 6 6    0 0 0
CELL_PARAMETERS angstrom
   5.633079685   0.000000000   0.000000000
   0.000000000   5.633079685   0.000000000
   0.000000000   0.000000000   3.982678150


ph.in

&inputph
  tr2_ph=4.0d-17,
  prefix='---',
  outdir='------',
  amass(1)=1.d0,
  amass(2)=79.9d0,
  amass(3)=14.d0,
  asr=.true.,
  zue=.true.,
  epsil=.true.,
  trans=.true.,
  fildyn='NH4Br.dyn.xml',
 /
0.0 0.0 0.0


dynmat.in

 &input
  fildyn='NH4Br.dyn.xml',
  asr='zero-dim'
 /

------------------------------------------------------------------------------------------
Why I am getting such kind of frequencies and how can I solve it? Any
suggestions is highly appreciated.

Thanking you in advance.
Pratik
Kolkata, India
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