[Wien] LDA-1/2 in Wien2k?

[Profa. Lara K. Teles]

Dear Sir:
    We are trying to use our LDA-1/2 method with WIEN2k. The method was very
succesful when used with VASP and SIESTA (PHYSICAL REVIEW B 78, 125116
(2008)) and we were able to calculate semiconductor band gaps with GW
precision, without appealing to parametrizations.
    Now we plan to use the method in a all-electron calculation. We elected
the WIEN2k code for our calculations. The idea is just to add an external
potential to the existing Kohn-Sham potential. Thus we plan to add our
potential to the potential in the file case.vsp, and this is simple because
clearly that file contains r*v and can be simply read, and add our
potential to case.vns. In the latter case we will not add to the
non-spherical parts inside the MT spheres because we think that such
addition should not be important. We plan to add to the Fourier expansion at
the end of the file. Now comes our questions:
1 - The entries of the Fourier expansion in the file case.vns are the
Fourier coefficients themselves, or their complex conjugate?
2 - The expansion is such that its value inside the spheres are zero or very
small? That is, integrals of the potential outside the spheres can be made
by integration in the whole cell?
3 - Is there a constant multiplying the Fourier coefficients?
4 - The expansion is in "stars", as defined in the book of Singh?
5 - When constructing the potential, is it wholly displaced to fix the zero
of energy? Where is the energy zero?
    Let us say that, in trying to understand how the potential is written in
the files,
we made simple tests adding a constant inside the spheres and the same
constant outside. Of course we were hoping to obtain the same eigenvalues,
perhaps displaced by a constant. That was not what we got.
    We hope you clear out our misunderstandings.
    It s worth pointing out that we do not intend to work against the
copyright, but only apply the LDA-1/2 approach to the several different
electronic structure methods.
Sincerely
LKT

PS - We think we understood the file case.clmsum containing the charge
density. Thus we could take our potential, calculate its Laplacian and add
the resulting charge density to the file case.clmsum (our charge density has
zero total charge). But there is a problem: the exchange-correlation of our
effective density would also be added. So this procedure would only work if
you taught us to run lapw0 setting no exchange-correlation. The potential
generated would be the one to be added to case.vsp and case.vns.

-- 
Profa. Dra. Lara Kühl Teles
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Instituto Tecnológico de Aeronáutica (ITA)
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