[Wien] Improving vacuum basis set

[Laurence Marks]

Thanks,

In fact the problem turned out to be due to the vacuum being too large
for a negatively charged cell calculation where one can (due to how
charged cells are currently calculated) get a potential valley in the
center with true vacuum states.

On 10/24/06, Torsten Andersen <thor at physik.uni-kl.de> wrote:
> Dear Mr. Marks,
>
> that it appears at z=0.5 is suspicious to me. I would suggest that you
> make your supercell larger (my experience says 12-16 vacuum "layers"
> plus epsilon), and that you change the cell size in the "vacuum"
> direction(s) to a non-integer multiple of the lattice parameter(s).
> Then, as a third option, increase GMAX and/or RMT*kmax.
>
> Alternatively, there is a film-LAPW code from Jülich which matches the
> vacuum with evanescent waves, as far as I remember.
>
> Best regards,
> Torsten Andersen.
>
> Laurence Marks wrote:
> > Not in fact an atom, rather the electron density. I'm getting some
> > relatively flat, small density (~1e-4 via lapw5/rhoplot) far from the
> > surface, which appears to be stabilized by it's exchange-correllation
> > energy (vxc potential around -0.1 at z=0.5). I'm not sure if it's
> > real, or whether the basis-set for this type of density might not be
> > poor.
> >
> > On 10/23/06, georg at chem.au.dk <georg at chem.au.dk> wrote:
> >
> >>Do you mean an atom some distance from (weakly bonded to) the surface?
> >>
> >>One thing is that WIEN sets the linearization energy to 0.30 because the
> >>fermienergy is "usually" around 0.5 Ry in densely packed solids, so 0.3Ry can
> >>be expected to be somewhere in the valence bands.
> >>
> >>If you have an atom the upper most state will have a negative energy so often
> >>the lineraization energy needs to be changed. As the bands are flat sometimes
> >>the energies have to be set very precisely. Maybe the -in1new option can help
> >>you.
> >>
> >> Best wishes Georg
> >>Quoting Laurence Marks <L-marks at northwestern.edu>:
> >>
> >>
> >>>I am running in to some issues with electrons at some distance from a
> >>>surface, and I suspect that I might not have the best basis set for
> >>>these in a conventional calculation. I'm wondering if anyone has
> >>>thought about this problem and come up with some ideas to try.
> >>>
> >>>--
> >>>Laurence Marks
> >>>Department of Materials Science and Engineering
> >>>MSE Rm 2036 Cook Hall
> >>>2220 N Campus Drive
> >>>Northwestern University
> >>>Evanston, IL 60208, USA
> >>>Tel: (847) 491-3996 Fax: (847) 491-7820
> >>>email: L-marks at northwestern dot edu
> >>>http://www.numis.northwestern.edu
> >>>_______________________________________________
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> >>>
> >>
> >>
> >>--
> >>Georg Madsen
> >>Department of Chemistry
> >>Aarhus University
> >>DK-8000 Århus C
> >>Denmark
> >>tlf (+45) 89423885
> >>http://www.chem.au.dk/~webuorg/gm
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> >>
> >
> >
> >
>
> --
> Dr. Torsten Andersen        TA-web: http://deep.at/myspace/
> AG Hübner, Department of Physics, Kaiserslautern University
> http://cmt.physik.uni-kl.de    http://www.physik.uni-kl.de/
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>


-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
http://www.numis.northwestern.edu