[Wien] setrmt_lapw

[John Rundgren]

Dear WIEN2k Team,

Thanks for setrmt_lapw info posted by Laurence, Peter, Gerhard, and
Peter, in order of emails appearing on my screen.

Peter's second info is glowing hot: "extend the potential from RMT onto
some larger sphere (e.g. a WS sphere)". Such an extension is exactly
what is desirable for the application of WIEN2k to LEED scattering phase
shifts.

New inquiry: How is such an extension made? Is a piece of code available
somewhere in W12.1?

My phase shift code has an entrance for case.clmsum and case.vcoul as
is. But for comparison of WIEN2k's self-consistence with Mattheiss's
direct superposition I need freedom of manipulation to greater radii
than those delivered by setrmt_lapw. 

With best wishes,
John
KTH


On Thu, 2012-09-13 at 22:59 +0200, Peter Blaha wrote:
> I do not know what exactly you need, but just a remark:
> 
> One can expand the interstitial potential (fourier series) into Besselfunctions
> from any center and thus "extend the potential from RMT on to some larger sphere (e.g. a WS sphere)
> 
> Am 13.09.2012 22:54, schrieb Fecher, Gerhard:
> > Dear John
> > I guess the rMTs of Wien2k have not much to do with the rMT you need for LEED
> > as it for example known from Pendry's LEED codes (KKR type) .
> >
> > To calculate the scattering phase shifts you will need to use the complete potential but
> > in Wien you have an interstitial and you don't know which part belongs to what atom.
> >
> > KKR is doing that for example in a different way, it does not come with an interstitial but uses
> > Wigner-Seitz spheres and shape functions to describe the full symmetry potential
> > (for examples see the code of Hubert Ebert or Jürgen Braun,
> > check J. Braun, Rep. Prog. Phys. 59, 1267 (1996), but he also has much more recent papers)
> >
> > Some years ago I tried to convert the potentials but gave up,
> > good luck, my best wishes are with you
> >
> > Ciao
> > Gerhard
> >
> > DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> > "I think the problem, to be quite honest with you,
> > is that you have never actually known what the question is."
> >
> > ====================================
> > Dr. Gerhard H. Fecher
> > Institut of Inorganic and Analytical Chemistry
> > Johannes Gutenberg - University
> > 55099 Mainz
> > ________________________________________
> > Von: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at]" im Auftrag von "Peter Blaha [pblaha at theochem.tuwien.ac.at]
> > Gesendet: Mittwoch, 12. September 2012 15:40
> > An: A Mailing list for WIEN2k users
> > Betreff: Re: [Wien] setrmt_lapw
> >
> > RMTs are NOT set according to ionic radii, smallest potential or charge
> > density discontinuity,.... (why, we have a full potential anyway !),
> > but solely by the requirements that the wavefunctions of different atoms in a cell
> > converge approximately at the same Kmax value (plane wave cutoff).
> >
> > We know that the convergence in APW goes approximately with RMT * Kmax.
> > Suppose H converges at RKmax=3, but O requires RKmax=6, then we set the radii as
> > 0.5 and 1.0 for H and O, such that Kmax=6 and R_H * Kmax=3 and R_O * Kmax=6.
> >
> > These rules have been found empirical by tests.
> >
> > Am 12.09.2012 14:39, schrieb John Rundgren:
> >> Dear Prof. Blaha et al.,
> >>
> >> Questions about setrmt_lapw:
> >>
> >> 1) rmt is generated by perl script setrmt_lapw, which takes data from
> >> SRC_nn/nn.f written by Schwarz and Blaha in 1988. Is the underlying
> >> theory described in any publication?
> >>
> >> 2) Since "initialize calc." begins from setrmt before setting XC and
> >> before starting "run SCF", I believe that setrmt is based on free-atom
> >> Coulombic potentials together with the crystal structure (so that the MT
> >> spheres do not overlap).
> >>
> >> However, another idea is that rmt be determined by the total potential =
> >> Coulombic potential + Madelung's electrostatic potential + XC
> >> interaction.
> >>
> >> Unfortunately, this would mean that setrmt be a part of "run SCF".
> >>
> >> 3) For a test I calculate LEED phase shifts (0-300 eV) for TiO2
> >> comparing setrmt with a method using total potential [PRB
> >> 68,125405(2003), Surf.Sci.602,1299(2008)]. The Attached diagram shows
> >> that the total scattering cross section depends significantly on the
> >> rmt's.
> >>
> >> The diagram is produced using Mattheiss's superposition potential. My
> >> dream is to use SCF potentials for LEED phase shifts.
> >>
> >> I am occupied by a write-up on rmt's and SCF potentials, and I would
> >> gratefully listen to your comments on the rmt matter.
> >>
> >> Best regards,
> >> John Rundgren
> >> KTH
> >>
> >>
> >>
> >> _______________________________________________
> >> Wien mailing list
> >> Wien at zeus.theochem.tuwien.ac.at
> >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> >>
> >
> > --
> >
> >                                         P.Blaha
> > --------------------------------------------------------------------------
> > Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> > Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
> > Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
> > --------------------------------------------------------------------------
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