[Pw_forum] problem with Xspectra

[matteo calandra]

Dear Min Wu,

  the pseudopotentials to be used for the absorbing atom
in Xspectra are those having
the label _gipaw, two examples are:

Fe.pbe-sp-mt_gipaw.UPF
Fe.star1s-pbe-sp-mt_gipaw.UPF

The first one has no core-hole and has full gipaw informations
while the second one has core-hole and full gipaw informations.
Gipaw informations mean many things. What you need to know is that
GIPAW informations include the presence of the
all-electron wavefunction for the 1s core state.

Now when you run a simulation you first need to calculate the charge
density in the presence of a core-hole and thus use pseudo
Fe.star1s-pbe-sp-mt_gipaw.UPF . This is done by a standard pw.x
scf calculation using this pseudo.
In a second step you need to calcuate the Xanes cross
section and this is done by the Xspectra code.

In the calculation of the  matrix element appearing in the
Xanes cross-section (Fermi golden rule) the initial 1s state
IN THE ABSENCE of a core hole is needed. This information is contanined
in the pseudo potential WITHOUT the core hole (Fe.pbe-sp-mt_gipaw.UPF).
Thus you simply extract this wavefunction using the script given with the
Xspectra disribution and you put the name of the file produced by the script
in the input file of the Xspectra program.

You cannot use the 1s core function with the core hole simply because this is
wrong as the matrix element inthe cross section involves the product
between the initial and final states and the initial state has no core hole.

M.
> Message: 1
> Date: Tue, 05 Oct 2010 00:42:50 +0800
> From: "wumindt2" <wumindt2 at zju.edu.cn>
> Subject: [Pw_forum] problem with Xspectra
> To: pw_forum at pwscf.org
> Message-ID: <MOFPODZWLMRBXFNKFMQBMVXTLUKC.wumindt2 at zju.edu.cn>
> Content-Type: text/plain; charset="gb2312"
>
> Hi,
>
> I'm a new user of Xspectra.
>
> In the Xspectra example given in the pwscf code, it calculates the  
> XAS using the pseudopotential
> without core hole level. In this case, we need to extract the core  
> wavefunction from the GIPAW
> pseudopotential when we run the xspectra.x.
>
> Now there are pseudopotentials with core hole, normally named as  
> *.star1s*.UPF. So here is
> my question, after the SCF calculation, do we still need to extract  
> the core wavefunction from the
> peusopotential of the absorbing atom?
>
> If the answer is yes, then why we choose the core wavefunction from  
> the pseudopotential as the ground
> state, rather than the core wavefunction after the SCF calculation?
>
> Thanks!
>
> Min Wu
> 2010-10-4


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