[Pw_forum] k points in epsilon.x
dev sharma
decboy9 at gmail.com
Mon Oct 12 13:59:50 CEST 2009
Thanks SIr, i will study Yambo or Sax.
Thanks,
Yours sincerely,
Dev ,
University of Delhi,
On Mon, Oct 12, 2009 at 3:59 PM, <marsamos at democritos.it> wrote:
> Dear User, for generating a kpoint grid supported by epsilon you can
> use the following small program (for pwscf input you have to specify
> nosym=.true., and KPOINTS crystal)
>
> program kpoints_gen
>
> integer :: ikz, iky, ikx, nk
> real :: weight
> real :: shiftx, shifty, shiftz
>
> read(*,*) nkx, nky, nkz, shiftx, shifty, shiftz
>
> nk=nkx*nky*nkz
> weight=1.0/real(nk)
> write(*,*) nk
> do ikz=1,nkz
> do iky=1,nky
> do ikx=1,nkx
>
> write(*,"(4f15.9)") (real(ikx)-real(1.0)+shiftx)/real(nkx),
> (real(iky)-real(1.0)+shifty)/real(nky), &
> (real(ikz)-real(1.0)+shiftz)/real(nkz), weight
>
> enddo
> enddo
> enddo
>
>
> end program kpoints_gen
>
>
> BUT I strongly suggest to you to use or the utilities inside SaX (see
> www.sax-project.org) or yambo (www.yambo-code.org) for calculating the
> dielectric constant. epsilon.x is not complete (it does not include the
> nonlocal part of the pseudo potential and is not able to include in the
> calculation the non-local field effects and excitonic effects). If YOU
> WORK WITH SEMICONDUCTORS OR INSULATORS YOU WILL NOT BE ABLE TO COMPARE
> WITH EXPERIMENTS. You should now which kind of RESPONSE you want to
> reproduce.
>
> bests
>
> layla
>
>
>
> Quoting Gabriele Sclauzero <sclauzer at sissa.it>:
>
> >
> >
> > dev sharma wrote:
> >> Sir, i want to calculate dielectric constant as a function of
> >> frequency. I have read the manual And it is written there that
> >> Epsilon.x doesn't support the reduction of the k-points grid into the
> >> unreducible Brillouin zone, so the previous PW runs must be performed
> >> with a uniform k-points grid and all k-points weights must be equal to
> >> each other, i.e. in the k-points card the k-points coordinates must be
> >> given manually in \emph{crystal} or \emph{alat} or \emph{bohr}, but not
> >> with the \emph{automatic} option.
> >
> > In your first mail you were speaking about the automatic keyword as
> > if it was an option
> > for a k-point list to be supplied to epsilon.x. As you have now
> > reported from the manual,
> > epsilon.x does not need a k-point grid, since it uses the k-points
> > from the underlying
> > data produced by the previous pw.x run.
> > For a cubic symmetry system, for instance, you can supply manually a
> > N x N x N mesh of
> > k-points (using crystal option might be the easiest solution, in my
> > opinion), which must
> > provide a good sampling the full BZ (it is not difficult to produce
> > one, see the source
> > code of pwtools/kpoints.f or PW/kpoint_grid.f90).
> > Be careful and check the code does not reduce the mesh by symmetry
> > (which is the default,
> > good behaviour of the code, that in this specific case you want to
> > avoid). Use the nosym
> > option if needed (as written in the manual).
> > You can also try to generate the grid with the automatic option of
> > K_POINTS after setting
> > to true nosym and noinv (see Doc/INPUT_PW.txt), but I'm not sure if
> > this always works.
> >
> >
> > Regards,
> >
> > GS
> >
> >
> >
> >> Thanks
> >>
> >> On Mon, Oct 12, 2009 at 12:40 PM, Gabriele Sclauzero <sclauzer at sissa.it
> >> <mailto:sclauzer at sissa.it>> wrote:
> >>
> >>
> >> dev sharma wrote:
> >> > hi 2 all,
> >> >
> >> > I have one question. In epsilon.x, the k points is not automatic
> >> > option. Sir, means how to give the K points option i.e. we have
> >> to give
> >> > only irreducible k points or like for the calculation ='bands' ,
> >> we have
> >> > give the path (like G{0,0,0}-->X(0.5,0,0)). If we have to give
> the
> >> > irreducible points , how to calculate those points ???? can i do
> >> this ,
> >> > that run the pw.x with a mesh like 4*4*4 grid and the number of
> k
> >> > points in the scf output are the required k points
> >>
> >> Never used this utility, so maybe my advice is useless: are you sure
> >> that epsilon.x does
> >> need a k-point grid on input? For what purpose are you using the
> >> program? Do you know what
> >> it computes? If not, please look at the documentation in
> >> Doc/eps_max.tex.
> >>
> >>
> >> GS
> >>
> >>
> >> PS: Please always sign your mails with your name and affiliation.
> Thanks
> >>
> >>
> >>
> >> --
> >>
> >>
> >> o ------------------------------------------------ o
> >> | Gabriele Sclauzero, PhD Student |
> >> | c/o: SISSA & CNR-INFM Democritos, |
> >> | via Beirut 2-4, 34014 Trieste (Italy) |
> >> | email: sclauzer at sissa.it <mailto:sclauzer at sissa.it>
> >> |
> >> | phone: +39 040 3787 511 |
> >> | skype: gurlonotturno |
> >> o ------------------------------------------------ o
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> >>
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> >
> > --
> >
> >
> > o ------------------------------------------------ o
> > | Gabriele Sclauzero, PhD Student |
> > | c/o: SISSA & CNR-INFM Democritos, |
> > | via Beirut 2-4, 34014 Trieste (Italy) |
> > | email: sclauzer at sissa.it |
> > | phone: +39 040 3787 511 |
> > | skype: gurlonotturno |
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