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Dear Abinit users:

Thank your for your reading my problem!
I got a strange phonon dispersion curves. I calculated phonon energies for 
some different q points.
In most cases, it looks good, but at some q points the phonon energies are 
very large, about several thousand cm-1. I don’t know what cause such strange 
large phonon energies.
I post the input file and the output file. I will be very appreciated for any 
help!

The input file:

ndtset   14
#Set 1 : ground state self-consistency
  getwfk1   0          
  kptopt1   1                                 
    nqpt1   0            
  tolvrs1   1.0d-18    
  rfphon1   0          
#Q vectors for all datasets
     nqpt   1                               
       qpt2       0.00000000E+00  0.00000000E+00  0.00000000E+00    
       qpt3       0.00000000E+00  0.00000000E+00  0.00000000E+00
       qpt4       2.50000000E-01  0.00000000E+00  0.00000000E+00
       qpt5       5.00000000E-01  0.00000000E+00  0.00000000E+00
       qpt6       2.50000000E-01  2.50000000E-01  0.00000000E+00
       qpt7       5.00000000E-01  2.50000000E-01  0.00000000E+00
       qpt8       5.00000000E-01  5.00000000E-01  0.00000000E+00
       qpt9       0.00000000E+00  0.00000000E+00  5.00000000E-01
       qpt10      2.50000000E-01  0.00000000E+00  5.00000000E-01
       qpt11      5.00000000E-01  0.00000000E+00  5.00000000E-01
       qpt12      2.50000000E-01  2.50000000E-01  5.00000000E-01
       qpt13      5.00000000E-01  2.50000000E-01  5.00000000E-01
       qpt14      5.00000000E-01  5.00000000E-01  5.00000000E-01
#Set 2 : Response function calculation of d/dk wave function 
    iscf2   -3      
  kptopt2   2         
  rfphon2   0          
  rfelfd2   2         
  tolvrs2   0.0       
  tolwfr2   1.0d-22   
#Set 3 : Response function calculation of Q=0 phonons and electric field pert.
  getddk3   2       
  kptopt3   2          
  rfelfd3   3         
#Sets 4-10 : Finite-wave-vector phonon calculations (defaults for all 
datasets)
   getwfk   1        
   kptopt   3         
   rfphon   1         
  rfatpol   1 6        
    rfdir   1 1 1     
   tolvrs   1.0d-8     
#Definition of the unit cell
acell 7.5985355706E+00  7.5985355706E+00  1.3397443718E+01 
rprim 1.0  0.0  0.0   
      0.0  1.0  0.0  
      0.0  0.0  1.0   
#Definition of the atom types
ntypat 3         
znucl 9 17 82     
#Definition of the atoms
natom 6         
typat 1 1 2 2 3 3      
      xred    0.0000000000E+00  0.0000000000E+00  0.0000000000E+00
              5.0000000000E-01  5.0000000000E-01  0.0000000000E+00
              0.0000000000E+00  5.0000000000E-01  6.4636449169E-01
              5.0000000000E-01  0.0000000000E+00 -6.4636449169E-01
              0.0000000000E+00  5.0000000000E-01  2.0872733663E-01
              5.0000000000E-01  0.0000000000E+00 -2.0872733663E-01
    nband   29         
      ixc   1            
     ecut   60.0     
    ngkpt   4  4  4          
    nshiftk   1            
   shiftk 0.5 0.5 0.5
     iscf   5        
    nstep   1000          
 diemac   4.0       

The output file for the phonon energies

The abnormal phonon at Phonon wavevector 0.25000  0.25000  0.00000; 0.50000  
0.50000  0.00000; 0.25000  0.25000  0.50000; 0.50000  0.50000  0.50000. There 
exists the large energies about several thousand cm-1. while others seem 
normal with the largest one about 300 cm-1.

 Phonon wavevector (reduced coordinates) :  0.00000  0.00000  0.00000
Phonon frequencies in cm-1    :
- -4.279038E+00 -4.272713E+00  4.373034E+00  4.917298E+01  4.917302E+01
-  8.612552E+01  8.612582E+01  9.715112E+01  1.144157E+02  1.393646E+02
-  1.393646E+02  1.644024E+02  1.798777E+02  1.798777E+02  2.336043E+02
-  2.455143E+02  2.455143E+02  2.949092E+02
  Phonon wavevector (reduced coordinates) :  0.25000  0.00000  0.00000
Phonon frequencies in cm-1    :
-  3.192804E+01  3.392083E+01  4.927854E+01  6.677409E+01  8.405157E+01
-  1.019854E+02  1.121193E+02  1.134872E+02  1.323993E+02  1.429140E+02
-  1.474018E+02  1.619763E+02  1.924395E+02  2.292376E+02  2.367425E+02
-  2.390494E+02  2.645327E+02  2.792528E+02
  Phonon wavevector (reduced coordinates) :  0.50000  0.00000  0.00000
Phonon frequencies in cm-1    :
-  4.623658E+01  4.637531E+01  6.176620E+01  6.177976E+01  1.075140E+02
-  1.078472E+02  1.269595E+02  1.276292E+02  1.432491E+02  1.434879E+02
-  1.460605E+02  1.463663E+02  2.122655E+02  2.189954E+02  2.274861E+02
-  2.304586E+02  2.588828E+02  2.611382E+02
  Phonon wavevector (reduced coordinates) :  0.25000  0.25000  0.00000
Phonon frequencies in cm-1    :
-  4.555156E+01  7.357367E+01  8.125790E+01  8.934373E+01  8.998305E+01
-  1.302243E+02  1.411050E+02  1.572370E+02  1.736949E+02  2.154605E+02
-  2.216928E+02  2.290339E+02  2.702617E+02  2.720580E+02  1.299044E+03
-  1.301870E+03  2.491297E+03  2.492445E+03
  Phonon wavevector (reduced coordinates) :  0.50000  0.25000  0.00000
Phonon frequencies in cm-1    :
-  5.392477E+01  5.394164E+01  6.341308E+01  6.342768E+01  1.035714E+02
-  1.037492E+02  1.151564E+02  1.158268E+02  1.352023E+02  1.352181E+02
-  1.570877E+02  1.570912E+02  1.852159E+02  1.863178E+02  2.203978E+02
-  2.206967E+02  2.724635E+02  2.729087E+02
  Phonon wavevector (reduced coordinates) :  0.50000  0.50000  0.00000
Phonon frequencies in cm-1    :
-  6.275207E+01  6.275761E+01  1.022723E+02  1.024415E+02  1.043890E+02
-  1.043928E+02  1.496535E+02  1.499704E+02  1.680470E+02  1.691888E+02
-  2.047381E+02  2.054285E+02  2.765027E+02  2.785749E+02  1.832179E+03
-  1.832195E+03  3.523518E+03  3.523636E+03
  Phonon wavevector (reduced coordinates) :  0.00000  0.00000  0.50000
Phonon frequencies in cm-1    :
-  2.481760E+01  2.481886E+01  4.827377E+01  4.827384E+01  5.892294E+01
-  9.590842E+01  1.009042E+02  1.009043E+02  1.195030E+02  1.195033E+02
-  1.644244E+02  1.853880E+02  1.855820E+02  1.855820E+02  2.336307E+02
-  2.443775E+02  2.443776E+02  3.587588E+02
  Phonon wavevector (reduced coordinates) :  0.25000  0.00000  0.50000
Phonon frequencies in cm-1    :
-  3.670399E+01  3.999837E+01  4.897277E+01  5.281315E+01  9.591533E+01
-  1.024686E+02  1.030269E+02  1.118549E+02  1.257712E+02  1.313344E+02
-  1.576650E+02  1.630150E+02  1.957273E+02  2.294008E+02  2.354659E+02
-  2.360860E+02  2.410068E+02  2.992700E+02
  Phonon wavevector (reduced coordinates) :  0.50000  0.00000  0.50000
 Phonon frequencies in cm-1    :
-  4.654286E+01  4.665432E+01  4.774321E+01  4.782902E+01  1.152466E+02
-  1.160208E+02  1.236515E+02  1.237080E+02  1.424104E+02  1.439222E+02
-  1.443342E+02  1.448216E+02  2.127744E+02  2.193770E+02  2.297358E+02
-  2.317711E+02  2.555331E+02  2.580663E+02
  Phonon wavevector (reduced coordinates) :  0.25000  0.25000  0.50000
Phonon frequencies in cm-1    :
-  4.844015E+01  7.524718E+01  8.084402E+01  9.020657E+01  1.004436E+02
-  1.249523E+02  1.347598E+02  1.544090E+02  1.797366E+02  2.121968E+02
-  2.222779E+02  2.295650E+02  2.364594E+02  2.799176E+02  1.299620E+03
-  1.302017E+03  2.491635E+03  2.492020E+03
  Phonon wavevector (reduced coordinates) :  0.50000  0.25000  0.50000
Phonon frequencies in cm-1    :
-  4.900866E+01  4.908555E+01  6.121504E+01  6.124819E+01  1.079681E+02
-  1.082573E+02  1.261325E+02  1.261610E+02  1.290467E+02  1.295480E+02
-  1.441531E+02  1.451253E+02  1.856025E+02  1.864816E+02  2.200743E+02
-  2.201720E+02  2.710332E+02  2.714365E+02
  Phonon wavevector (reduced coordinates) :  0.50000  0.50000  0.50000
Phonon frequencies in cm-1    :
-  6.242250E+01  6.242690E+01  1.001331E+02  1.002546E+02  1.073382E+02
-  1.073962E+02  1.473111E+02  1.476311E+02  1.633786E+02  1.691719E+02
-  2.069319E+02  2.074886E+02  2.550029E+02  2.643759E+02  1.832636E+03
-  1.833175E+03  3.523455E+03  3.523601E+03