[Wien] setrmt_lapw

Peter Blaha pblaha at theochem.tuwien.ac.at
Fri Sep 14 16:42:55 CEST 2012 

I see. You want to replace the "full potential" with a "ASA" potential, where the WS-spheres are
equal to the unit cell volume (and overlap !)

At least schematically such code is certainly in WIEN2k, but of course not directly usable.

E.g. in SRC_lapw0/lapw0.F   the coulomb potential in the interstital (written as Fourier series)
is expanded into "Besselfunctions" for R=RMT  (and you want to have it for R-values, which are
gt. RMT). The relevant code lines are:

         DO J=2,NKK

           ARG=RMT(JATOM)*ABSK(J)
           CALL SPHBES(lmax2+1,ARG,BES)
           CALL YKAV(J,JATOM,YKA,LMMTMX,LMMULT,LLMM)
           LMMULT1=0

           DO LM1=1,LLMM
             L=IABS( LM(1,LM1,JATOM) )
             M=LM(2,LM1,JATOM)
             LMMULT1=LMMULT1+1
             IF (LMMULT1.NE.1) THEN
               IF ((L.EQ.IABS(LMMULT(1,LMMULT1-1,JATOM))).AND. &
                 (M.EQ.LMMULT(2,LMMULT1-1,JATOM))) THEN
                 LMMULT1=LMMULT1-1
               endif
             endif
             CVOUT(LM1)=CVOUT(LM1) + POTK(J)*BES(L)*YKA(LMMULT1)
           ENDDO

This loops over all K of the fourier series, and in the second line
you would put "your" R (instead of RMT).
Then you calculate the besselfunctions and the spherical harmonics.

Maybe you need only LM1=Ll,m=0,0  spherical part ?

remember: exp(iKr)= 4 pi SUM_l (imag**l bes(K.r) * Y_LM(r) * conjg(Y_LM(K)) )

Regards

Am 14.09.2012 14:17, schrieb John Rundgren:
> Dear WIEN2k Team,
> Thanks for setrmt_lapw info posted by Laurence, Peter, Gerhard, andPeter, in order of emails appearing on my screen.
> Peter's second info is glowing hot: "extend the potential from RMT ontosome larger sphere (e.g. a WS sphere)". Such an extension is exactlywhat is desirable for the application of WIEN2k to LEED scattering phaseshifts.
> New inquiry: How is such an extension made? Is a piece of code availablesomewhere in W12.1?
> My phase shift code has an entrance for case.clmsum and case.vcoul asis. But for comparison of WIEN2k's self-consistence with Mattheiss'sdirect superposition I need freedom of manipulation to greater radiithan those delivered by setrmt_lapw.
> With best wishes,JohnKTH
>
> 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 no
t 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/> > --------------------------------------------------------------------------> > _______________________________________________> > Wien mailing list> > Wien at zeus.theochem.tuwien.ac.at> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien> > _______________________________________________> > Wien mailing list> > Wien at zeus.theochem.tuwien.ac.at> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien> >>
>
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>

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                                       P.Blaha
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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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