Dear Mr. Gironcoli
Thanx for your answer, but sorry I'm not sure i follow you, could you open it
more?!
you mean in the case of periodic perturbation(like the constant one) we have a
change in the # of electrons? what exactly happens in this case, so we have to
shift the Fermi energy(in order to have neutrality condition)? What happens if
we do not shift it(As you see i want you to answer the question you made!)?
Thanx again
Ezad Shojaee - Tehran University
> At any q/=0 the perturbation is such that the number of electrons does > not
> change.> Even in the limit of q->0 the macroscopic term in the density
> response > is zero (because in a metal> the dielectic constant is infinite).>
> Now consider the case of a periodic (q=0) perturbation, the simplest > one, a
> constant, threated with or w/o the FE shift... which of the two > treatments
> corresponds to the result you would obtain in the liimit q->0 ?
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