The ABINIT Users Mailing List ( CLOSED )

[Hua Bao <hbao@purdue.edu>]

Dear Anglade and all,

Thank you for your fruitful suggestions. The calculation gets much 
better and faster convergence now.

Here another problem made the calculation stops again.
It stuck in dataset 4, where the calculation need the information of 
wavefunction from dataset one.
The error message in the log file is
inwffil: ERROR
-P-0000   The file trf2_1o_DS1_WFK cannot be used to start the
-P-0000   present calculation. It was asked that the wavefunctions be 
accurate, but
-P-0000   at least one of the k points could not be generated from a 
symmetrical one.
-P-0000   dksqmax=    2.333543E-04
-P-0000   Action: check your wf file and k point input variables
-P-0000     (e.g. kptopt or shiftk might be wrong in the present dataset 
or the preparatory on

I followed the tutorial and used a file similar to trf2_2.in to generate 
the necessary q points. Base on the error message, it seems to be a k 
point grid problem. Though ABINIT determined the correct space group 
(167), it seems that the k point grid generated by "kptopt 1" in dataset 
1 is not enough for the further calculation (in dataset 4). I tried to 
use "kptopt 0" so that all the dataset will use the same grid, but it 
won't work, either. My questions, how to choose appropriate k points 
(with ngkpt, nshiftk shiftk, kptopt...) for all the dataset for my 
system? (Rhombohedral, Corundum, primitive cell)

Below is the input data.

Thank you very much.

Hua Bao

********************************************************************************
  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-16    # Use wave function residual criterion instead
 nline2 15
#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
#######################################################################
#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
npulayit 20
#Definition of the SCF procedure
   nstep   500        # Maximal number of SCF cycles








Anglade Pierre-Matthieu wrote:
> On Dec 2, 2007 5:13 AM, Hua Bao <hbao@purdue.edu 
> <mailto:hbao@purdue.edu>> wrote:
>
>     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?
>
>
>
> On the one hand, tolvrs is the "real" convergence criterion for SCF 
> loop, because it is the measure of the change of the potential between 
> iterations; because Eigenvalues of the SCF cycles range (almost) 
> between 1 and inifinity, having tolvrs=0 means that your calculation 
> is converged. On the other hand it is quite possible to find not at 
> all converged calculations where toldfe and toldff are zero making 
> them unreliable convergence criterion.
>
> Tolwfr monitor the convergence of wave functions during the non-SCF 
> optimisation. Response function formalism is based on those wave 
> functions (cf some articles of X. Gonze in PRB). If I don't mistake, 
> all RF equations implemented into Abinit become true when the energy  
> is at its minimum with respect to wavefunctions. Experience tells 
> that  any error in the wavefunctions leads to dramatic errors in the 
> RF quantities (because those are derivatives of the energy).
>
>  
>
>
>     Second, is it OK to use a less strict criteria to achieve a easier
>     convergence? How much can it affect the output (phonon dispersion)?
>
>
>
> 2nd question: Dramatically.
> 1st question: Yet is it OK try to do the calculation with various 
> settings for tolwfr and  monitor  the convergence.
>  
>
>
>     My input file is attached.
>
>
>
> Good idea: I see that you do not use nnsclo and nline. Try to increase 
> those two variables and you will likely get a much better convergence. 
> For a first guess try nline=15 ...
>
>
> Regards
>
> PMA
>