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[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

Hello Tao,

this is indeed very strange, and you should definitely have an LO-TO
splitting. Do you have the convergence information for the DDK run?
Could it be that it did not converge? The rest of your input looks
quite correct. You might send a tarball of all the outputs, if they
are not too heavy.

Cheers

Matthieu

On Mon, Mar 23, 2009 at 6:05 PM,  <gaotaoscu@hotmail.com> wrote:
> Dear All,
>
> When I try to reproduce the TO-LO splitting for CaF2 (original paper: 
> PHYSICAL
> REVIEW B vol68, 195123,2003),I got no LO-TO splitting in my calculation.
> According to the experiments and the theoretical calculation, there should 
> have
> a TO-LO splitting in Gamma point for CaF2, but my input file is not able to 
> let
> these kind of slitting. my version is abinit-5.4.4p, and pseudopotential is
> '20ca.pspnc' and '9f.pspnc'. Below is my setting for the DDB and phonon 
> parts,
> and the related output, any comments or suggestion is appreciated.
>
> 1,Generation of the derivative databases,
> # Crystalline CaF2 : computation of the phonon spectrum
>
>   ndtset   10
>  getwfk1   0            # Cancel default
>  kptopt1   1            # Automatic generation of k points, taking
>                         # into account the symmetry
>    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-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-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 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 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
> #Definition of the unit cell
>    acell   3*10.3232         # 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
>            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 are two types of atom
>    znucl   20 9     # The keyword "znucl" refers to the atomic number of the
>                      # possible type(s) of atom. The pseudopotential(s)
>                      # mentioned in the "files" file must correspond
>                      # to the type(s) of atom. Here, type 1 is the Aluminum,
>                      # type 2 is the Arsenic.
>
> #Definition of the atoms
>    natom   3         # There are two atoms
>    typat   1 2 2       # The first is of type 1 (Al), the second is of type 
> 2
> (As).
>    xred                      # 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   11
>    occopt  3
> #Exchange-correlation functional
>
>      ixc   1             # LDA Teter Pade parametrization
>
> #Definition of the planewave basis set
>
>     ecut   26.0           # Maximal kinetic energy cut-off, in Hartree
>
> #Definition of the k-point grid
>    ngkpt   4  4  4
>  nshiftk   4              # Use one copy of grid only (default)
>   shiftk   0.0 0.0 0.5    # This gives the usual fcc Monkhorst-Pack grid
>            0.0 0.5 0.0
>            0.5 0.0 0.0
>            0.5 0.5 0.5
>
> #Definition of the SCF procedure
>    iscf     7        # Self-consistent calculation, using algorithm 5
>    nstep   1500      # Maximal number of SCF cycles
>    diemac   9.0      # Although this is not mandatory, it is worth to
>                      # precondition the SCF cycle. The model dielectric
>
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
> 2,computation of phonon band structures
>
> !Input file for the ifc code. Analysis of the CaF2 DDB
> !Flags
>  ifcflag   1     ! Interatomic force constant flag
>
> !Wavevector grid number 1 (coarse grid, from DDB)
>  brav    2      ! Bravais Lattice : 1-S.C., 2-F.C., 3-B.C., 4-Hex.)
>  ngqpt   4  4  4   ! Monkhorst-Pack indices
>  nqshft  1         ! number of q-points in repeated basic q-cell
>  q1shft  3*0.0
>
> !Effective charges
>     asr   1     ! Acoustic Sum Rule. 1 => imposed asymetrically
>  chneut   1     ! Charge neutrality requirement for effective charges.
>
> !Interatomic force constant info
>  dipdip  1      ! Dipole-dipole interaction treatment
>
> !Phonon band structure output for band2eps - See note near end for
> ! dealing with gamma LO-TO splitting issue.
>   eivec  4
>
> !Wavevector list number 1 (Reduced coordinates and normalization factor)
>
>  nph1l    80      ! number of phonons in list 1
>
>  qph1l       0.00000000E+00  0.00000000E+00  0.00000000E+00  1.0
>              5.00000000E-02  2.50000000E-02  2.50000000E-02  1.0
>              1.00000000E-01  5.00000000E-02  5.00000000E-02  1.0
>                  .........................................
>              5.00000000E-01  4.50000000E-01  5.50000000E-01  1.0
>              5.00000000E-01  4.75000000E-01  5.25000000E-01  1.0
>              5.00000000E-01  5.00000000E-01  5.00000000E-01  1.0
>
> !Wavevector list number 2 (Cartesian directions for non-analytic gamma 
> phonons)
>
> !The output for this calculation must be cut-and-pasted into the
> ! t59_out.freq file to be used as band2eps input to get proper LO-TO
> ! splitting at gamma.  Note that gamma occurrs twice.
>
>  nph2l    1       ! number of directions in list 2
>
>  qph2l   1.0  0.0  0.0    0.0
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
> 3, output of LO-TO splitting.
>     ........................................................
>  Treat the second list of vectors
> -begin at tcpu      0.470  and twall      0.957 sec
>  Phonon at Gamma, with non-analyticity in the
>  direction (cartesian coordinates)  1.00000  0.00000  0.00000
>  Phonon energies in Hartree :
>   0.000000E+00  0.000000E+00  0.000000E+00  1.634493E-03  1.634494E-03
>   1.634498E-03  1.962988E-03  1.962988E-03  1.962990E-03
>  Phonon frequencies in cm-1    :
> -  0.000000E+00  0.000000E+00  0.000000E+00  3.587298E+02  3.587300E+02
> -  3.587309E+02  4.308260E+02  4.308260E+02  4.308265E+02
> +Total cpu time      0.470  and wall time      0.959 sec
>  anaddb : the run completed succesfully.
>
> Regards,
>
> Tao
>



-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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