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

Hello David,

interesting problem, and it will be good to see a comparison with CASTEP.

1) is your system metallic? And do you have enough unoccupied bands.
It sounds like the rest of your things are well converged, so I'll
presume so.

2) your acoustic modes may be /= 0 because of a breaking of the
acoustic sum rule. This is due to pseudopotentials essentially
(through the xc part) - you might search for ASR in the mail archives,
it has come up often. 80cm-1 does seem quite large, though, as an ASR
error.

3) your high 2000 cm-1 modes are definitely wrong. Could you send the
log/output so we can see if all the perturbations actually converged?

4) the warnings you saw are unimportant: in one case the kpoints will
be completed by symmetry (you can get rid of the warning by using the
same kptopt in the GS and RF cases) and in the other the energy is
almost stationary so it is not possible to lower it using the CG.

5) If the system is really metallic, you probably need a lot more
k-points. This could be the source of error.
Are you sure the 8x8x8 + 4 shifts is equivalent to the kptrlatt grid
you use for the response functions? I don't think so (it should be -8
8 8   8 -8 8    8 8 -8), and this could explain why the RF is
(spectacularly) bad.

Matthieu

On Mon, May 4, 2009 at 2:08 PM,  <dat36@cam.ac.uk> wrote:
> Dear All,
>            I am having trouble finding correct phonon frequencies at Gamma 
> for
> the d-metal system Ag5Pb2O6. I have calculated them before in the CASTEP
> plane-wave code and wanted to repeat the calucation in ABINIT as a sanity 
> check
> before using ABINIT to consider more properties.
>
> With the following input file I am able to calculate an accurate band
> structure, and I then use the WFK file from the SCF calculation as the 
> input to
> my response function calculation.
> # Ag5Pb2O6 BS
> #
> # Computation of the band structure.
> # First, a SCF density computation, then a non-SCF band structure 
> calculation.
>
> ndtset 2
>
> #Dataset 1 : usual self-consistent calculation
> kptopt1 1          # Option for the automatic generation of k points,
>                   # taking into account the symmetry
> nshiftk1 4
> shiftk1  0.5 0.5 0.5  # These shifts will be the same for all grids
>         0.5 0.0 0.0
>         0.0 0.5 0.0
>         0.0 0.0 0.5
> ngkpt1  8 8 8
> prtden1  1         # Print the density, for use by dataset 2
> toldfe1  1.0d-8
>
> #Dataset 2 : the band structure
> iscf2    -2
> getden2  -1
> kptopt2  -4
> nband2   100
> ndivk2   28 19 29 45     # 10, 12 and 17 divisions of the 3 segments, 
> delimited
>                       # by 4 points.
> kptbounds2 0.0 0.0 0.0
> 0.5 0.0 0.0
> 0.333333 0.333333 0.0
> 0.0 0.0 0.0
> 0.0 0.0 0.5
>
> tolwfr2  1.0d-16
> #enunit2  1             # Will output the eigenenergies in eV
>
>
> #Definition of the unit cell
> acell 3*1.8897        # This is equivalent to   1 Angstrom each
> rprim
>        5.137609105410803      -2.966200000000002       0.000000000000000
>        0.000000000000000       5.932400000000000       0.000000000000000
>        0.000000000000000       0.000000000000000       6.410500000000000
>
>
> #Definition of the atom types
> ntypat 3
> znucl 8 47 82
>
>
> #Definition of the atoms
> natom 13           # There are two atoms
> typat 1 1 1 1 1 1 2 2 2 2 2 3 3
> xred              # This keyword indicate that the location of the atoms
>                  # will follow, one triplet of number for each atom
>    0.6222000122070313   0.0000000000000001   0.6888999938964855
>   -0.0000000000000001   0.6222000122070313   0.6888999938964855
>   -0.6222000122070311  -0.6222000122070314   0.6888999938964854
>   -0.0000000000000001  -0.6222000122070314  -0.6888999938964855
>   -0.6222000122070311   0.0000000000000001  -0.6888999938964855
>    0.6222000122070313   0.6222000122070313  -0.6888999938964854
>    0.0000000000000000   0.0000000000000000   0.2413000017404568
>    0.0000000000000000   0.0000000000000000  -0.2413000017404568
>    0.5000000000000000  -0.0000000000000000   0.0000000000000000
>    0.0000000000000000   0.5000000000000001   0.0000000000000000
>   -0.5000000000000000  -0.5000000000000001  -0.0000000000000000
>    0.6666666666666667   0.3333333333333334   0.5000000000000001
>   -0.6666666666666667  -0.3333333333333334  -0.5000000000000001
> #Definition of the planewave basis set
> ecut 40.0         # Maximal kinetic energy cut-off, in Hartree
>
> #Definition of the SCF procedure
> nstep 100          # Maximal number of SCF cycles
>       # Although this is not mandatory, it is worth to
>                  # precondition the SCF cycle. The model dielectric
>                  # function used as the standard preconditioner
>                  # is described in the "dielng" input variable section.
>
> occopt 7
> tsmear 0.007
>
>
>
> The input for the response function calculation for the density matrix at 
> Gamma
> is:
> # Crystalline Ag5Pb2O6: computation of the dynamical matrix at Gamma
> #
>
> #Response-function calculation, with q=0
>  rfphon   1            # Will consider phonon-type perturbation
>  rfatpol   1 13          # All the atoms will be displaced
>   rfdir   1 1 1        # Along all reduced coordinate axis
>    nqpt   1            # One wavevector is to be considered
>     qpt   0 0 0        # This wavevector is q=0 (Gamma)
>  kptopt   2            # Automatic generation of k points, taking
>                        # into account the time-reversal symmetry only
>  tolvrs   1.0d-8       # SCF stopping criterion
>    iscf   5            # Self-consistent calculation, using algorithm 5
>  irdwfk   1            # Read the ground-state wavefunctions
>
>
> #######################################################################
> #Common input variables
>
> #Definition of the unit cell
> acell 3*1.8897        # This is equivalent to   1 Angstrom each
> rprim
>        5.137609105410803      -2.966200000000002       0.000000000000000
>        0.000000000000000       5.932400000000000       0.000000000000000
>        0.000000000000000       0.000000000000000       6.410500000000000
>
>
> #Definition of the atom types
> ntypat 3          # There is only one type of atom
> znucl 8 47 82          # 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, the only type is Silicon.
>
>
> #Definition of the atoms
> natom 13           # There are two atoms
> typat 1 1 1 1 1 1 2 2 2 2 2 3 3
> xred              # This keyword indicate that the location of the atoms
>                  # will follow, one triplet of number for each atom
>    0.6222000122070313   0.0000000000000001   0.6888999938964855
>   -0.0000000000000001   0.6222000122070313   0.6888999938964855
>   -0.6222000122070311  -0.6222000122070314   0.6888999938964854
>   -0.0000000000000001  -0.6222000122070314  -0.6888999938964855
>   -0.6222000122070311   0.0000000000000001  -0.6888999938964855
>    0.6222000122070313   0.6222000122070313  -0.6888999938964854
>    0.0000000000000000   0.0000000000000000   0.2413000017404568
>    0.0000000000000000   0.0000000000000000  -0.2413000017404568
>    0.5000000000000000  -0.0000000000000000   0.0000000000000000
>    0.0000000000000000   0.5000000000000001   0.0000000000000000
>   -0.5000000000000000  -0.5000000000000001  -0.0000000000000000
>    0.6666666666666667   0.3333333333333334   0.5000000000000001
>   -0.6666666666666667  -0.3333333333333334  -0.5000000000000001
> #Definition of the planewave basis set
> ecut 40.0         # Maximal kinetic energy cut-off, in Hartree
> diemac 1000000
>
> #Definition of the SCF procedure
> nstep 100          # Maximal number of SCF cycles
>       # Although this is not mandatory, it is worth to
>                  # precondition the SCF cycle. The model dielectric
>                  # function used as the standard preconditioner
>                  # is described in the "dielng" input variable section.
> occopt 7
> tsmear 0.007
>
> #Definition of the k-point grid
> kptrlatt -4  4  4      # In cartesian coordinates, this grid is simple 
> cubic,
> and
>          4 -4  4      # actually corresponds to the so-called 8x8x8
> Monkhorst-Pack grid.
>          4  4 -4      # It might as well be obtained through the use of
>                       # ngkpt, nshiftk and shiftk .
>
> #Gives the number of band, explicitely (do not take the default)
> nband  70               # For an insulator (if described correctly as an
> insulator
>                       # by DFT), there is no need to include conduction 
> bands
>                       # in response-function calculations
>
> #Exchange-correlation functional
> ixc 1             # LDA Teter Pade parametrization
>
> I obtain the following phonon frequencies:
>  Phonon frequencies in cm-1    :
> -  8.173847E+01  8.385767E+01  9.066616E+01  9.157959E+01  9.161629E+01
> -  1.007493E+02  1.056726E+02  1.056770E+02  1.167382E+02  1.169064E+02
> -  1.215102E+02  1.215114E+02  1.273660E+02  1.273693E+02  1.359495E+02
> -  1.436825E+02  1.559343E+02  1.559382E+02  2.079336E+02  2.079848E+02
> -  2.190082E+02  2.002110E+03  2.002542E+03  2.003094E+03  2.003199E+03
> -  2.008633E+03  2.010303E+03  2.010572E+03  2.012517E+03  2.022057E+03
> -  2.022089E+03  2.022721E+03  2.025986E+03  2.037439E+03  2.038421E+03
> -  2.039042E+03  2.039143E+03  2.039784E+03  2.040022E+03
>
> However, I expected to see three acoustic phonons and none above 500cm^-1.
>
> There were two types of warning in the output file, for example:
> -P-0000  hdr_check: WARNING -
> -P-0000   input nkpt=     128 not equal disk file nkpt=      52
>
> -P-0000  cgwf3: WARNING -
> -P-0000   New trial energy at line       4 =  -4.421412E+02
> -P-0000      is higher than former: -4.421412E+02
>
> Any help is much appreciated.
>
> Thanks,
> David Tompsett.
>



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