[WIEN]a question on lapw0

[Peter Blaha]

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 

> Dear Professor Blaha:
>    I still have a problem on the choice of the zero-point of the potential 
> when I wonder the coherent energy of a crystal.Because we all know an 
> electron energy in atom is definded as the negative value of the energy 
> needed of moving it to infinity from the atom.While in WIEN2K,the total 
> energy of a crystal is calculated with potential zero-point defined as the 
> average of the potential in the interstitial region.I could understand that 
> 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.
> 
>    As far as I could understand I believe that there MUST BE a constant 
> added to both sides of the Schrodinger Equation so that it could give the 
> correct total-energy and generally speak,this constant is not the same one 
> from differnent system.My question is how to determin this constant in source 
> procedure of Lapw0 and whether it is possible to detect it from the output-
> files such as case.output0 and/or case.scf0?(I have confirmed that :VZERO 
> just only meaningful for slab but not for crystal itself)
> 
>    In my opinion this is an important and elementary question.Maybe my 
> consider is not correct,please pointit out and I really want to grasp the 
> spirit of WIEN2k more completely.Expect your patient and kind reply eagerly!
> 
>    Best Regards!
>                                                         your sincerly Jun
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                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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