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[Sophie Green <us_sophie.green@yahoo.com>]

Hi,
I am very appreciate with your reply. I don't know how to enlarge the presicion in input file to give the correct symmetry. I checked the input variables, and still no results. 
I want to do the convergence tests, and I choose one point Gamma as what was done in the Si calculations in the test. Whether this method (choosing one point) is feasible? Besides, what is the meaning of ppmfrq in the input file? How we choose this value corresponding with our case?


The following is my input file.
kptopt1  1            # Option for the automatic generation of k points,
nkpt1    432
ngkpt1   12 6 12
nshiftk1 1
shiftk1  0.5 0.5 0.5  # These shifts will be the same for all grids
# Definition of the SCF procedure
toldfe1  1.0d-6    # Will stop when this tolerance is achieved on total
 energy
prtden1  1         # Print out density

# Dataset2: calculation of kss file
# Definition of k-points
kptopt2  0              # K-points will be provided
nkpt2    1              # Take only 1 k-point:
kpt2     0.0  0.0  0.0  # the Gamma point
istwfk2  1              # Option needed for special k-points like Gamma
# Definition of the SCF procedure
iscf2    -2             # Non self-consistent calculation
getden2  -1             # Read previous density file
tolwfr2 
 1.0d-10        # Still get it converged
nband2   13

# Definition of parameters for the calculation of the kss file
nbandkss2 -1        # Number of bands in KSS file (the maximum possible)
# Dataset3: Calculation of the screening (epsilon^-1 matrix)
optdriver3  3
getkss3     -1
nband3      37
ecutwfn3    3.6
ecuteps3    6.0
ppmfrq3    16.7 eV

# Definition of the unit cell: fcc
acell  4.827496 8.976202 5.427863        # This is equivalent to   10.217 10.217 10.217
rprim   0.500000  0.929695  0.000000   # FCC primitive vectors (to be scaled by acell)
       -0.500000  0.929695  0.000000
       
 0.000000  0.000000  1.124364

# Definition of the atom types
ntypat  1         # There is only one type of atom
znucl 1           # 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 12           # There are two atoms
typat  1 1 1 1 1 1 1 1 1 1 1 1       
 # They both are of type 1, that is, Silicon.
xred              # Reduced coordinate of atoms
     0.50359   0.50359   0.63530
     0.63171   0.63171   0.95315
     0.76831   0.76831   0.81692
     0.99641   0.99641   0.13530
     0.86829   0.86829   0.45315
     0.73169   0.73169   0.31692
     0.00359   0.00359   0.86470
     0.13171   0.13171   0.54685
     0.26831   0.26831   0.68308
     0.49641   0.49641   0.36470
     0.36829  
 0.36829   0.04685
     0.23169   0.23169   0.18308

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 8.0          # Maximal kinetic energy cut-off, in Hartree

# Use only symmorphic operations
symmorphi 0

# Definition of the SCF procedure
nstep   20        # Maximal number of SCF cycles
diemac  12.0      # 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.
                  # Here, we follow the prescription for bulk silicon.

timopt -1
# This line added when defaults were changed (v5.3) to keep the previous, old behaviour
  iscf 5

There is no ERR or WARN message in the output file, except that the wrong space group (monoclinic).

Thanks very much for your help.

Best Wishes,

Sophie
Anglade Pierre-Matthieu <anglade@gmail.com> wrote:

Hi,

Usually Abinit understand input structures correctly. If it tells you
that your input is monoclinic, it is quite likely this is true and it
may matter a lot for your calculation if it is supposed to be
orthogonal. Sometimes this kind of errors results from lack of
numerical precision in the input file. Don't forget to use fraction,
sqrt ... wherever relevant . The best for other people to tell you
what is going wrong is to post your input file at least. May be some
part of your output would be usefull too.

About GW calculation: For as much as I know you just have to give
Abinit the coordinates of each k-point you want to include. For
instance if you want to use standard monkhorst pack gris plus some
k-point you can first generate the list of coordinates for the
monkhorst pack and then use kptopt 0, nkpt and kpt to specify the
point you are interested in.

regards

PMA

On Sun, Mar 23, 2008 at 11:22 AM, Sophie Green
wrote:
> I am a new user to Abinit. I looked through the tutorial. I want to
> calculate band gap with GW. I gave the conventional unit cell parameters
> (acell) and rprim, also the atomic positions. But the output file shows
> that the space group is monoclinic (P2_1/c). But it should be
> orthogonal (cmca). I don't know why the space group is wrong. Will this
> cause
> mistake in the following calculations?
> Besides, If the point I want to calculate in GW is nonspecific point,
> what should I do to conclude this point in KSS calculation?
> If anyone has this experience, please instruct me. Thanks in advance.
>
>
> ________________________________
>
> Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it
> now.



--
Pierre-Matthieu Anglade

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