[WIEN]a question on lapw0

[Jiang Jun]

Dear Professor:
    In fack I have read the faq about "positive Fermi-energies" for so many 
times and I know it clearly that the the choice of potential zero-point is 
arbitrary and no physical meaning and also keep it in mind that the total-
Energy does NOT depend on this choice.BUT,I think it is too simple to 
interpret its really meaning in "faq" as below:

"Eigenvalues, core states, linearization energies, the Fermi energy,... are 
given in Rydberg units in wien2k, and are relative to a zero-point that is 
defined as the average of the potential in the interstitial region. This is 
an arbitrary choice……This has no physical meaning, and it is also not an 
indication of a possible error, it is just due to the choice of the zero-
point.

For a free atom, the choice of zero is arbitrary as well, but if one makes 
the usual convention that the potential at infinity is zero, then negative 
and positive energies indicate bound and unbound states, respectively. This 
is intuitively appealing. But for solids, there is nothing special about 
infinity: the solid is everywhere, also at infinity. Therefore, another 
convention has to be made, like the one explained above.
Please note, the TOTAL-Energy does NOT depend on this choice!!!) "


For me,It is very important to know where and how to choose the zero-point of 
potential.That is why I am buring with curious to know how to do THIS CHOICE 
again and again.Anyway，I am not satisfied with only the answer of faq and I 
don't think it is all the story also.

I am sorry for my reply with less politeness.I wish you are patient and nice.

> This topic was discussed 100 times in the mailing list (please search the 
> mailing list) and there is also a  "faq" page about "positive 
> Fermi-energies" at www.wien2k.at 

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