[Wien] setrmt_lapw

[Peter Blaha]

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
>>
>>
>>
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>>
>
> --
>
>                                         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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-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
-----------------------------------------