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["hyello25 Qgrui" <hyello25@gmail.com>]

Dear all,

When did some frozen phonon calculation with abinit-5.3.5, I found that it is very hard to get a convergence situation in the system I studied.

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A coarse calculation condition:

       ecut     75.0           
     ngkpt     5 5 8 
   tsmear     0.001

 Phonon energies in Hartree :
  -6.897964E-05 -6.874225E-05 -1.610995E-05  5.995451E-04  9.154624E-04
   9.154693E-04  1.481579E-03  1.838560E-03  2.164959E-03  2.164959E-03
   2.634642E-03  2.634645E-03  2.788635E-03  2.788642E-03  3.711178E-03
   3.925329E-03  6.579701E-03  6.589587E-03
 Phonon frequencies in cm-1    :
- -1.513928E+01 -1.508718E+01 -3.535725E+00  1.315849E+02  2.009208E+02
-  2.009223E+02  3.251691E+02  4.035173E+02  4.751536E+02  4.751536E+02
-  5.782371E+02  5.782378E+02  6.120347E+02  6.120361E+02  8.145094E+02
-  8.615102E+02  1.444077E+03  1.446247E+03

-------------------------------------------------------------------------------------------------------------------------

A fine calculation  condition:

       ecut     80.0           

     ngkpt     6 6 10 
   tsmear     0.001

 Phonon energies in Hartree :
   1.084946E-04  1.161357E-04  1.161383E-04  6.044373E-04  9.131515E-04
   9.131528E-04  1.525057E-03  1.636784E-03  2.137862E-03  2.137862E-03
   2.665797E-03  2.665817E-03  2.815919E-03  2.815945E-03  3.739180E-03
   3.906673E-03  6.385868E-03  6.443097E-03
 Phonon frequencies in cm-1    :
-  2.381182E+01  2.548884E+01  2.548942E+01  1.326587E+02  2.004136E+02
-  2.004139E+02  3.347114E+02  3.592325E+02  4.692064E+02  4.692064E+02
-  5.850749E+02  5.850793E+02  6.180227E+02  6.180285E+02  8.206551E+02
-  8.574156E+02  1.401536E+03  1.414096E+03
------------------------------------------------------------------------------------------------------------------------

A ultra-fine condition:

       ecut     90.0           
     ngkpt     8 8 12 
   tsmear     0.001

 Phonon energies in Hartree :
   1.077808E-04  1.120975E-04  1.120975E-04  6.029432E-04  9.131937E-04
   9.131937E-04  1.525790E-03  1.629333E-03  2.125484E-03  2.125484E-03
   2.663839E-03  2.663839E-03  2.811991E-03  2.811991E-03  3.722566E-03
   3.888009E-03  6.341715E-03  6.484394E-03
 Phonon frequencies in cm-1    :
-  2.365515E+01  2.460256E+01  2.460256E+01  1.323307E+02  2.004229E+02
-  2.004229E+02  3.348722E+02  3.575972E+02  4.664899E+02  4.664899E+02
-  5.846451E+02  5.846451E+02  6.171607E+02  6.171607E+02  8.170088E+02
-  8.533194E+02  1.391846E+03  1.423160E+03
-------------------------------------------------------------------------------------------------------------------------
    All  results above are at the end of DATASET 3.

    Though the gamma phonon frequencies have achieved convergence at the _fine_ and _ultra-fine_ condition,  the acoustics branch freq. at Gamma are not close be ZERO. Does this matter?  Why dose this situation come out ?
    When the Gamma point have reach convergence, dose this mean that other Q point will have a good convergence as well?

    To a metallic system, which type of "occopt" is more reasonable ? I found "occopt=3" was very hard to do phonon calculate successfully then  "occopt=7".
    

Thanks in advance.
Bests.

Qian

Dept. of Physics, NJU
CN

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The input file is below, with some information omitted.
------------------------------------------------------------------------------------------------------------------
   ndtset   3
   jdtset   1 2 3  
 
   occopt  7  
   tsmear  0.001
  
#Set 1 : ground state self-consistency
  getwfk1   0            # Cancel default
  kptopt1   1            # Automatic generation of k points, taking
                         # into account the symmetry
    nqpt1   0            # Cancel default
  tolvrs1   1.0d-20      # SCF stopping criterion (modify default)
  rfphon1   0            # Cancel default
#Q vectors for all datasets
     nqpt   1            # One qpt for each dataset (only 0 or 1 allowed)

# Q-point 5x5x8
   qpt2     0.00000000E+00  0.00000000E+00  0.00000000E+00
qpt3              0.00000000E+00  0.00000000E+00  0.00000000E+0
qpt4              2.00000000E-01  0.00000000E+00  0.00000000E+00
qpt5              4.00000000E-01  0.00000000E+00  0.00000000E+00
qpt6              2.00000000E-01  2.00000000E-01  0.00000000E+00
qpt7              4.00000000E-01  2.00000000E-01  0.00000000E+00
qpt8              4.00000000E-01  4.00000000E-01  0.00000000E+00
qpt9              0.00000000E+00  0.00000000E+00  1.25000000E-01
qpt10              2.00000000E-01  0.00000000E+00  1.25000000E-01
qpt11              4.00000000E-01  0.00000000E+00  1.25000000E-01
qpt12              2.00000000E-01  2.00000000E-01  1.25000000E-01
qpt13              4.00000000E-01  2.00000000E-01  1.25000000E-01
qpt14              4.00000000E-01  4.00000000E-01  1.25000000E-01
qpt15              0.00000000E+00  0.00000000E+00  2.50000000E-01
qpt16              2.00000000E-01  0.00000000E+00  2.50000000E-01
qpt17              4.00000000E-01  0.00000000E+00  2.50000000E-01
qpt18              2.00000000E-01  2.00000000E-01  2.50000000E-01
qpt19              4.00000000E-01  2.00000000E-01  2.50000000E-01
qpt20              4.00000000E-01  4.00000000E-01  2.50000000E-01
qpt21              0.00000000E+00  0.00000000E+00  3.75000000E-01
qpt22              2.00000000E-01  0.00000000E+00  3.75000000E-01
qpt23              4.00000000E-01  0.00000000E+00  3.75000000E-01
qpt24              2.00000000E-01  2.00000000E-01  3.75000000E-01
qpt25              4.00000000E-01  2.00000000E-01  3.75000000E-01
qpt26              4.00000000E-01  4.00000000E-01  3.75000000E-01
qpt27              0.00000000E+00  0.00000000E+00  5.00000000E-01
qpt28              2.00000000E-01  0.00000000E+00  5.00000000E-01
qpt29              4.00000000E-01  0.00000000E+00  5.00000000E-01
qpt30              2.00000000E-01  2.00000000E-01  5.00000000E-01
qpt31             4.00000000E-01  2.00000000E-01  5.00000000E-01
qpt32              4.00000000E-01  4.00000000E-01  5.00000000E-01


#Set 2 : Response function calculation of d/dk wave function 

    iscf2   -3         # Need this non-self-consistent option for d/dk
  kptopt2   2          # Modify default to use time-reversal symmetry
  rfphon2   0          # Cancel default
  rfelfd2   2          # Calculate d/dk wave function only
  tolvrs2   0.0        # Cancel default for d/dk
  tolwfr2   1.0d-23    # Use wave function residual criterion instead

#Set 3 : Response function calculation of Q=0 phonons and electric field pert.

  getddk3   2          # d/dk wave functions from last dataset
  kptopt3   2          # Modify default to use time-reversal symmetry
  rfelfd3   3          # Electric-field perturbation response only

#Sets 4-10 : Finite-wave-vector phonon calculations (defaults for all datasets)

   getwfk   1          # Use GS wave functions from dataset1
   kptopt   3          # Need full k-point set for finite-Q response
   rfphon   1          # Do phonon response
  rfatpol   1 6        # Treat displacements of all atoms
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-13     # This default is active for sets 3-10

  rprim    1         0         0
           0         1         0
           0         0         1

   acell    9.2375514607E+00  9.2375514607E+00  5.4464293933E+00 

nband   25
#Definition of the plane wave basis set
   ecut   90.0       # coarse : 75Ha    
 diemix   0.20

#Definition of the k-point grid
  ngkpt   8 8 12    # coarse : 5x5x8 
nshiftk   1              
 shiftk   0.5  0.5  0.5
#Definition of the self-consistency procedure
 iprcel   45
  nline   15
   iscf   3         
  nstep   200