The ABINIT Users Mailing List ( CLOSED )

[Hua Bao <hbao@purdue.edu>]

Dear Abinit-user,

I am trying to do a phonon dispersion calculation using "respond 
function" in Abinit.  I followed the response function 2 in the 
tutorial. It used tolvrs 1d-18 for the first dataset, and tolwfr 1d-22 
for the second and tolvrs 1d-8 for the others. However, I find that the 
convergence criteria is quite difficult to achieve for my system (after 
100 steps, tolvrs is only about 1d-2).

I have two questions here.
First, why these criteria are chosen for response function calculation 
over toldff and toldfe?
Second, is it OK to use a less strict criteria to achieve a easier 
convergence? How much can it affect the output (phonon dispersion)?

My input file is attached.

Thanks,
Hua Bao


INPUT
###################################################################
 ndtset   13
#Set 1 : ground state self-consistency

 getwfk1   0            # Cancel default
 kptopt1   1            # Automatic generation of k points, taking
                        # into account the symmetry
   nqpt1   0            # Cancel default
 tolvrs1   1.0d-12      # SCF stopping criterion (modify default)
 rfphon1   0            # Cancel default

#Q vectors for all datasets

#Complete set of symmetry-inequivalent qpt chosen to be commensurate
# with kpt mesh so that only one set of GS wave functions is needed.
#Generated automatically by running GS calculation with kptopt=1,
# nshift=0, shiftk=0 0 0 (to include gamma) and taking output kpt set
# file as qpt set. Set nstep=1 so only one iteration runs.

    nqpt   1            # One qpt for each dataset (only 0 or 1 allowed)
                        # This is the default for all datasets and must
                        #  be explicitly turned off for dataset 1.

    qpt2   0.00000000E+00  0.00000000E+00  0.00000000E+00
    qpt3   0.00000000E+00  0.00000000E+00  0.00000000E+00
    qpt4    1.25000000E-01  1.25000000E-01  1.25000000E-01
    qpt5    3.75000000E-01  1.25000000E-01  1.25000000E-01
    qpt6   -3.75000000E-01  1.25000000E-01  1.25000000E-01
    qpt7   -1.25000000E-01  1.25000000E-01  1.25000000E-01
    qpt8    3.75000000E-01  3.75000000E-01  1.25000000E-01
    qpt9   -3.75000000E-01  3.75000000E-01  1.25000000E-01
    qpt10  -1.25000000E-01  3.75000000E-01  1.25000000E-01
    qpt11  -3.75000000E-01 -3.75000000E-01  1.25000000E-01
    qpt12   3.75000000E-01  3.75000000E-01  3.75000000E-01
    qpt13  -3.75000000E-01  3.75000000E-01  3.75000000E-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-12    # 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 2        # 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

 prtwf4 0
prtwf5 0
prtwf6 0
prtwf7 0
prtwf8 0
prtwf9 0
prtwf10 0
prtwf11 0
prtwf12 0
prtwf13 0
#######################################################################
#Common input variables

#Definition of the unit cell
acell 3*9.6937
 angdeg 3*55.33
 ecut 28.0
 natom 10
 nband 30
 xred    3.5211402820E-01  3.5211402820E-01  3.5211402820E-01
         5.5932966859E-01  9.4067033141E-01  2.5000000000E-01
         2.5000000000E-01  5.5932966859E-01  9.4067033141E-01
         9.4067033141E-01  2.5000000000E-01  5.5932966859E-01
         8.5211402820E-01  8.5211402820E-01  8.5211402820E-01
         4.4067033141E-01  5.9329668593E-02  7.5000000000E-01
         7.5000000000E-01  4.4067033141E-01  5.9329668593E-02
         5.9329668593E-02  7.5000000000E-01  4.4067033141E-01
         6.4788597180E-01  6.4788597180E-01  6.4788597180E-01
         1.4788597180E-01  1.4788597180E-01  1.4788597180E-01
 typat    1  2  2  2  1  2  2  2  1  1
#Definition of the atom types
  ntypat   2         # There are two types of atom
   znucl   13 8     # 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.

  diemac   9.0
#Definition of the k-point grid
   ngkpt   4  4  4         
 nshiftk  1
 shiftk  0.5  0.5  0.5
#Definition of the SCF procedure
   nstep   100        # Maximal number of SCF cycles