[Pw_forum] Xspectra calculation (wumindt2)

[Matteo Calandra]

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" <wumindt2 at zju.edu.cn>
> Subject: Re: [Pw_forum] Xspectra calculation
> To: pw_forum at pwscf.org
> Message-ID: <VAKPWQRCYLTHVSRAHCOSTHTPZOSR.wumindt2 at zju.edu.cn>
> 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,
>