AW: [WIEN]Why Fermi Energy is positive

[Gerhard Fecher]

The energy zero is, roughly speaking, the zero of the muffin tin potential, separating the atomic like potentials from the "free" band electrons.

Youre question was, why postive energies in atoms are unstable, but these belong to free electrons and not to bound ones. The energy of a free electron scattered by a atom or molecule should always be >0, that does not imply that the solution is unstable.

Ciao
Gerhard

-----Ursprüngliche Nachricht-----
Von: wien-bounces at zeus.theochem.tuwien.ac.at im Auftrag von Jiang Jun
Gesendet: Sa 15.04.2006 05:30
An: A Mailing list for WIEN2k users
Betreff: Re: [WIEN]Why Fermi Energy is positive
 
Anyway thank you very much for your soon reply!

Yeah.You are quite right,Energies of free electrons are always positive.
But,E(tot)=E(kinetic)+E(potential)

Here,E(Kinetic)>0.
Then if E(Potential)<0, Maybe E(tot) be <0.

In fact,I Do NOT suspect that there were something wrong with WIEN2K that 
leads to the Fermi-Energy be positive and What I wonder and much more care 
is: Where is the ZERO point of Potential in the Crystial-Calculation and What 
is its Physical means?

I believe just for the choice of the point of reference-potentical,part of 
the EIGENVALUES become positive.Maybe this is a elementary question in LAPW.

Best wishes!
                                               Sincerely Jun
> Energies of free electrons are always positive as the kinetic energy 1/2 m 
v^2 cannot be negytive (if neglecting inelastic approximations).
> 

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