[Pw_forum] xspectra calculation

[wumindt2]

Dear Matteo,

So when we just do the dipolar part, we don't need to care about the
k vector, right?

Besides, in order to  compare with an experimental spectrum, is it necessary to cut
the occupied state below Fermi energy level within our Xspectra calculation ?
In that case, we should set "cut_occ_states" = .true. and 
"ef_r" equal to the fermi energy we got in the scf calculation. Is it?

Best regards,

Min Wu
2010-10



>From: Matteo Calandra <matteo.calandra at impmc.jussieu.fr>
>Reply-To: PWSCF Forum <pw_forum at pwscf.org>
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] xspectra calculation
>Date: Tue, 19 Oct 2010 16:28:30 +0200
>
>Dear Min Wu,
>
> >
> >It seems i have found the problem. It's not the problem of the
> >xcoordcrys. I set it as .true. and the polarization vectors are 
>(0,0,1) >and
> >(0,1,0). The xray k vector is the default value (1,0,0).
> >BTW, can we use the same vector for polarization and xay k moment?
> >e.g. Both of them are (1,0,0). Is it OK?
>
>Of course epsilon and k MUST be ortogonal otherwise what you are doing
>is meaningless. If you calculate the dipolar part only then
>the k-vector is not used and can take any value.
>
> >
> >The problem i found is that i set the "cut_occ_states" = .true.
> >Then it cut all the occupied state that i expected to see.
> >When i reset it to .false., i saw the expected peak.
> >
>
>Maybe your ef_r is not in the correct units... Of course you put the
>Fermi level in the presence of a core-hole, don't you ?
>
> >I have another problem, what does the "ef_r" do in the calculation?
> >For instance, i got fermi level of -5 eV with scf calculation.
> >The i set ef_r= -5/13.6 Ry. Then, in the calculated xspectra data, 
> >where is
> >the Fermi level? It is ajusted to 0 eV, or still is the -5 eV?
> >
>
>zero, the energies are simply shifted.
>
>M.
>
>-- 
>* * * *
>Matteo Calandra, Charge de Recherche (CR1)
>Institut de Minéralogie et de Physique des Milieux Condensés de Paris
>Université Pierre et Marie Curie, tour 16, case 115
>4 Place Jussieu, 75252 Paris Cedex 05 France
>Tel: +33-1-44 27 52 16       Fax: +33-1-44 27 37 85
>http://www.impmc.jussieu.fr/~calandra
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