[Pw_forum] Xspectra calculation (wumindt2)

[wumindt2]

Dear Matteo,

Thanks for the information, i read the C. Brouder the paper a little bit.
I'am still not sure how to choose the polarization vector.
For instance, we have a crystal with spacegroup of P42/MNM, point group of 4/mmm.
According to the Table in C. Brouder's paper, this is a dichroism compound.
Thus, how can we choose the polarization vector when calculating the XAS
of this compound?
Can you please show me how? 

Thanks so much!

Cheers,

Min Wu
2010-10-12


>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 (wumindt2)
>Date: Mon, 11 Oct 2010 10:08:16 +0200
>
>Dear
>
>  I assume you are talking of the dipolar part only.
>For the quadrupolar it is substantially more complicate.
>The number of independent calculations that you have
>to perform to obtain the isotropic cross section (powder)
>depends on the  point group of the space group
>of your crystal.
>It is 1 for a cubic or tetraedric crystal,
>2 for a uniaxial crystal and it is 3, 4, 6 for a biaxial
>(ot trichroic) crystal.
>I suggest you read
>C. Brouder J. Phys.: Condens. Matter 2 (1990) 701-738
>for more details.
>
>M.
>
>
>> 
>> Message: 3
>> Date: Sat, 09 Oct 2010 22:48:53 +0800
>> From: "wumindt2"

>> Subject: Re: [Pw_forum] Xspectra calculation
>> To: pw_forum at pwscf.org
>> Message-ID:

>> Content-Type: text/plain;	charset="gb2312"
>> 
>> Dear matteo,
>> 
>> Thanks. 
>> 
>> For dichroism compound, do we just need the in-plane and the c-axis
>> polarization vectors? 
>> While for trichroism compound, do we need to calculate three different
>> polarization vectors?
>> Am i right?
>> 
>> Best regards,
>> 
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