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[ธนูสิทธิ์ บุรินทร์ประโคน <thanusit@kku.ac.th>]

           screening main loop
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Dear Matteo Giantomassi

I have tried using the standard procedure to specify the k-grid for KSS
file generation, as you suggested.  As a result, the subsequent
screening calculation was successfully completed. So, I think the
problem is solved.

Kind Regards,
Thanusit Burinprakhon



> On May 15, 2008 1:01:49 AM ICT, "Matteo Giantomassi"
<Matteo.Giantomassi@uclouvain.be> wrote:
> 
> 
> 
> >
> > Dear Matteo Giantomassi
> > Thank you very much for your reply. I will try as you suggested on
the KSS
> > file generation.
> > Since the k-grid for screening calculation is the same as the mesh
used to
> > generate the KSS file, does it mean that Abinit will take the k-grid
> > directly from the KSS file without any need to input separately the
k-grid
> > for the screening run?
> 
>   Yes, you are right, most of the basic quantities needed by GW
>   are read from the KSS file. However you have to specify
>   the k-mesh in the input file otherwise abinit will stop
>   while parsing the input file
> 
> 
> > Kind Regards,
> > Thanusit Burinprakhon
> >
> >
> > On May 13, 2008 10:12:58 PM ICT, "Matteo Giantomassi"  wrote: > Dear All
> >>
> >> I've tried to perform the GW corrections for GaP band structue. My
> >> platform is Fedora 8.0 running on an Intel Core 2 Quad CPU with 4 Gb
> >> of RAM. I firstly calculated the ground state density and the KSS file,
> >> by using the parallelized Abinit 5.4.4(MPI version, prepared for a
> >> x86_64_linux) and the Abinit 5.4.4(sequential version, prepared for a
> >> x86_64_
> >> linux), respectively. Both calculations were successfully completed.
> >>
> >> However, when I carried out the screening calculation using the
> >> parallelized
> >> Abinit 5.4.4 with the pre-calculated KSS file, the program seemed to
> >> terminate
> >> within the screening main loop at the start of the "cchi0" calculation
> >> of
> >> the
> >> q point number 2. The error message at the end of the log file is as
> >> follows.
> >> The
> >> complete input and log files are listed below. (sorry if it's very
> >> lengthy)
> >>
> >> ....................................................................
> >> cchi0 : enter
> >>
> >> use symmetries = 0
> >> use time reversal = F
> >> spectral method = 0
> >> calculating chi0(q,omega,G,G")
> >>
> >>
> >> cchi0 : reading wavefunctions from file
> >> trying to allocate wavefunctions in real space
> >> allocated
> >> cchi0 : real space wavefunctions are now in memory
> >>
> >> calculation status ( 865 to be completed) :
> >> cchi0 : ik = 1 / 865 is = 1 done by processor 0
> >> cchi0 : ik = 2 / 865 is = 1 done by processor 0
> >>
> >> cchi0 : ERROR -
> >> kp=k-q-G0 not found
> >> ik = 3 k = 0.166667 0.166667 0.083333
> >> k-q = 0.250000 0.333333 0.083333
> >> -P-0000
> >> -P-0000 leave_new : decision taken to exit ...
> >> ......................................................................
> >>
> >
> >
> > Dear Thanusit Burinprakhon
> >
> > The difference between k-q and k should be a reciprocal lattice vector.
> > In your case the first two reduced components of k and k-q
> > do not cancel each other. I think the problem is in the k-mesh
> > used to generate the KSS file.
> >
> > Can you check if the errors shows up also if the k-mesh is specified
> > using the "standard" procedure, namely using ngkpt and nshiftk and
shiftk.
> > You might try the values used in the GW tutorial for silicon:
> >
> > # Dataset2: calculation of kss file
> > # Definition of k-points
> >
> > ngkpt2 4 4 4 (or 6 6 6)
> > nshiftk2 4
> > shiftk2 0.0 0.0 0.0 # This grid contains the Gamma point
> > 0.0 0.5 0.5
> > 0.5 0.0 0.5
> > 0.5 0.5 0.0
> >
> > You have to run these tests only to check if abinit finds
> > all the points it needs, so you can safely decrease
> > ecutwfn, ecuteps and .nbands during the tests.
> >
> >>
> >> I also have another question on the screening issue. Does Abinit need
> >> the
> >> k-point
> >> grid for screening calculations?
> >
> > Of course, the k-grid is the same as the mesh used to generate the KSS
> > file.
> > The dielectric matrix is calculated for a set of q-points that are given
> > by all the possible difference between two k-points (taking into account
> > symmetries)
> >
> > Hope this helps
> > Regards
> > Matteo Giantomassi
> >
> >
> >
> >
> >
> >
> 
>