The ABINIT Users Mailing List ( CLOSED )

[<dat36@cam.ac.uk>]

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.