The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Dear iloveabinit@gmail.com ,

It is likely that, for each of the problematic q points, one  
perturbation
(out of 18 for each q point : 6 atoms times three) did not converge.
In the following, I will suppose this is the case
(you could check whether some of the WARNING
messages were indicating a convergence problem).

If I am not mistaken, according to your input file, your material is  
insulating.
You have set nband to a larger value than the set of valence bands  
only. This
is usually fine, but it might be that the higher bands get degenerate  
for some
k points, and that in some cases, the limit is just set at these  
degenerate bands.
This might hamper the convergence.
As a consequence, you might try to set nband at precisely the number  
of occupied bands.
(Likely 28, if your psp for Pb treats d electrons as valence).

Note that you do not need to redo all perturbations, only those that  
did not converge.
I am not completely sure how MRGDDB will perform the merge, as it  
might be clever
enough to erase the old data, and use the new one. If this does not  
work, erase
the erroneous data in the DDB by hand (should not be too difficult !).

If adjusting nband does not work, you might try to change iscf ...

Good luck,
Xavier


On 25 Sep 2006, at 13:41, iloveabinit@gmail.com wrote:

> 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