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[GaoTao <gaotaoscu@hotmail.com>]

Hi Matthieu,

Thanks for your analysis.  The computation crashed at the start of Dataset 4.  
 
Yes, my oxide compound is a semiconductor with only about 1.2 eV bandgap. I used to try to set 'nband 9' to seperate these degenerate valence state, but failed. I am also sure there are no ghost states  in my pseudopotential because they are the standard pseudopotential downloaded from abinit website. I am thinking about whether LDA+U can be combined with phonon calculation in ABINIT. Or is there any other option in ABINIT to deal with these kind of small bandgap materials?
 
Best,
 
Tao
 
response
> Date: Fri, 3 Apr 2009 19:05:10 +0200
> From: matthieu.jean.verstraete@gmail.com
> To: forum@abinit.org
> Subject: Re: [abinit-forum] How to change occopt, consistently, in GS and RF calculations for insulator
>
> Check your ground state output to see what the spectrum looks like. I
> suspect you will find the system actually is metallic.
>
> If not, it happens quite frequently that a perturbation makes it
> metallic, especially if the gap is very small. This makes convergence
> quite difficult (you might try changing diemac for the phonon runs, I
> think iprcel does not work for RF). You could also try to change
> occopt for the phonon runs, but again you will find it refuses to
> allow the LO-TO splitting calculation at some point... If your system
> has a large gap none of this should be happening. Check geometries and
> compostition etc... Maybe the pseudopotentials have a ghost state...
>
> Which dataset is crashing?
>
> Matthieu
>
>
>
> On Fri, Apr 3, 2009 at 12:43 PM, <gaotaoscu@hotmail.com> wrote:
> > Dear All,
> >
> > I get some contradictory suggestions from the phonon calculation error
> > displayed in ABINIT. On the one hand, my oxide compund(insulator) request the
> > 'occopt 1', otherwise there will have no LO-TO splitting. However, when the
> > 'occopt 1' option were filled in the input file, the calculation error will
> > suggest you to 'change occopt, consistently, in GS and RF calculations'. Will
> > you have any suggestion on this problem? Thank you very much in advance.
> >
> > Best,
> >
> > Tao
> >
> > PS, here is my input file. and error displayed.
> > 1) input file,
> > # Crystalline : computation of the phonon spectr um
> >   ndtset   10
> > #Set 1 : ground state self-consistency
> >
> >  getwfk1   0            # Cancel default
> >  kptopt1   1            # Automatic generation of k points, taking
> >  nqpt1   0            # Cancel default
> >  tolvrs1   1.0d-18      # 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)
> >
> >     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        -2.50000000E-01  2.50000000E-01  0.00000000E+00
> >     qpt9        5.00000000E-01  5.00000000E-01  0.00000000E+00
> >     qpt10       -2.50000000E-01  5.00000000E-01  2.50000000E-01
> >
> > #Set 2 : Response function calculation of d/dk wave function
> >
> >  iscf2   -3         # Need this non-self-con sistent option for d/dk
> >  kptopt2   2   &n bsp;      # 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-22    # 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 calculat ions (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 3        # Treat displacements of all atoms
> >   rfdir   1 1 1      # Do all directions (symmetry will be used)
> >   tolvrs   1.0d-8     # This default is active for sets 3-10
> >
> > #Common input variables
> >    acell   3*10.349007457  Bohr         # This is equivalent to   10.61 10.61
> > 10.61
> >    rprim  0.0  0.5  0.5   # In lessons 1 and 2, these primitive vectors
> &g t;           0.5  0.0  0.5   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1
> >           0.5  0.5  0.0   # that is, the default.
> >
> > #Definition of the atom types
> >   ntypat 2         # There is tow type of atom
> >   znucl ---   ---      # The keyword "znucl" refers to the atomic number of
> > the
> >
> > #Definition of the atoms
> >   natom 3           # There are two atoms
> >   typat 1 2 2         # They both are of type 1, that is, Silicon.
> >   xred              # This keyword indicate that the location of the atoms
> >                  # will follow, one triplet of number for each atom
> >   0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of atom 1.
> >   1/4  1/4  1/4  # Triplet giving the REDUCED coordinate of atom 2.
> >   3/4  3/4  3/4              # Note the use of fractions (remember the limited
> >
> >
> > #Gives the number of band, explicitely (do not take the default)
> >    nband   12
> >    occopt 1
> > #Exchange-correlation functional
> >
> >      ixc   11             # LDA Teter Pade parametrization
> >
> > #Definition of the planewave basis set
> >
> >     ecut   28.0
> > #Definition of the k-point grid
> >    ngkpt   4  4  4
> >    nshiftk   4              # Use one copy of grid only (default)
> >    shiftk 0.5 0.5 0.5
> >          0.5 0.0 0.0
> >          0.0 0.5 0.0
> >          0.0 0.0 0.5
> >
> > #Definition of the SCF procedure
> >     iscf   7          # Self-consistent calculation, using algorithm 5
> >     nline  15
> >    nstep   1000         # Maximal number of SCF cycles
> >   diemac   12.0        # Although this is not mandatory, it is worth to
> >                       # precondition the SCF cycle. The model dielectric
> >
> > 2) error displayed,
> >
> >     iter   2DEtotal(Ha)        deltaE(Ha) residm    vres2
> >  scfcv3, nstep=        1000> >
> >  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  36  36  36
> >         ecut(hartree)=     28.000   => boxcut(ratio)=   2.06526
> >  scfcv3, nstep=        1000
> > -P-0000  occeig : ERROR -
> > -P-0000   In a non-metallic case (occopt<3), for a RF calculation,
> > -P-0000   if the eigenvalues are degenerate, the occupation numbers must also
> > be degenerate.
> > -P-0000   However, the following pair of states gave :
> > -P-0000   k -state, band number   9, occ=    2.000000E+00, eigenvalue=
> > -2.507767E-01,
> > -P-0000   kq-state, band number  10, occ=    0.000000E+00, eigenvalue=
> > -2.507767E-01.
> > -P-0000   Action : change occopt, consistently, in GS and RF c alculations.
> > -P-0000
> > -P-0000  leave_ne w : decision taken to exit ...
> > -P-0000  leave_new : synchronization done...
> > -P-0000  leave_new : exiting...
> >
>
>
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Dr. Matthieu Verstraete
>
> European Theoretical Spectroscopy Facility (ETSF)
> Dpto. Fisica de Materiales,
> U. del Pais Vasco,
> Centro Joxe Mari Korta, Av. de Tolosa, 72, Phone: +34-943018393
> E-20018 Donostia-San Sebastian, Spain Fax  : +34-943018390
>
> Mail : matthieu.jean.verstraete@gmail.com
> http://www-users.york.ac.uk/~mjv500
>

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