[Wien] vcoul

[Peter Blaha]

Hi,
I'm not sure I understand exactly what you did.

Anyway: put R2V (instead of NR2V) in case.in0 and you get the coulomb potential
in a file case.vcoul (format as  case.clmval), you can plot it using lapw5, or
you can have a look at the spherical symmetric part V_00(r).

Is this what you took in (1) ???

(2) I cannot imagine how one gets a proper coulomb potential form clmsum00 alone.
     (what about ZZ ??; what should be a "neutral muffin-tin" ???, it can hardly be
     neutral ??.
     for sure, the charges from outside the sphere affects the potential inside the sphere.

In fact, in lapw0 the coulomb-pot at RMT is determined solely from the plane wave
part !    You may have a look at M.Weinert's paper, according to which the potential
is calculated.

Am 29.11.2011 14:24, schrieb John Rundgren:
> Dear Wien2k Team,
> This is about vcoul(L,M=0,0) generated by Fe3O4 and Sr3Mn2O7. I compare
> two potential curves as functions of radius R:
>
> (1) VC(R)=vcoul00(R)/sqrt(4*pi), spherically symmetric;
> (2) VCpois(R), spherically symmetric, obtained from clmsum00 and
> Poisson's equation (using subroutine charg2.f). My boundary condition of
> PE is the conventional one giving zero VCpois for a neutral muffin-tin
> and large R.
>
> In summary, I expect that VC and VCpois are equal up to a constant,
> individual for individual atoms depending on the SCF boundary condition
> in Wien2k. Results for Fe3O4 and Sr3Mn2O7:
>
> Fe3O4, Table for potential value at RMT:
>          Fe1   Fe2   O
> VC     -0.13  0.18  0.37
> VCpois -2.03 -2.08 -1.15
> VCpois(R)=VC(R)+const with great accuracy.
>
> Sr3Mn2O7 with RMT's from setrmt_lapw, Table for potential value at RMT:
>          Sr1   Sr2   Mn    O1    O2    O3
> VC     -472  -382  -231  -258  -230  -250
> VCpois -2.0  -2.0  -2.6  -7.3  -7.5  -7.0
>
> First observation: the values differ by factors 35-235. How is the
> boundary condition for vcoul defined in Wien2k?
>
> Second observation: dVC/dR is<0 and dVCpois/dR is>0 for R in the
> neighborhood of RMT. Indeed, the latter behavior corresponds to a
> muffin-tin with negative charge.
>
> Third observation: VCpois(R) .neq. VC(R)+const. The disagreement is
> significantly great, see 1st Attachment.
>
> When the Fe3O4 calculation is used for LEED, the agreement
> theory-experiment is satisfactory [Surf.Sci. 602(2008)1299]. On the
> other hand, a LEED investigation on Sr3Mn2O7 would respond badly on a
> potential disagreement like the one demonstrated in the 1st Attachment.
> 2nd Attachment is SR3Mn2O7.struct.
>
> VC versus VCpois is a dilemma for Sr3Mn2O7. Is there an expert's input
> to w2web that would make the potentials equal? A discussion would be
> much appreciated.
>
> With best regards,
> John Rundgren, KTH, Stockholm
>
>
>
>
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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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